Manley TNT User manual

4/19/11revCD
SECTION PAGE
INTRODUCTION 3
BACK PANEL & CONNECTING 4
FRONT PANEL 5
BEGINNINGS 6
IMPEDANCE 8
TUBE CHANNEL 10
COOL CHANNEL 13
TROUBLESHOOTING 19
CURVES 20
MAINS CONNECTIONS 24
SPECIFICATIONS 25
APPENDIX 1 - TEMPLATE FOR STORING SETTINGS 26
CONTENTS

INTRODUCTION
THANK YOU !
For choosing the Manley TNT Microphone Preamplier. The name of this mic preamplier “TNT” is
a reference to the two different channels, one that is Tube and the other No Tube. We see people today
hungry for a variety of preamps as a means of getting a variety of sounds and tones from the start. Of
course, mic selection and mic position can produce a wider variety of colors, but once that is locked
in, the preamp choice can be a signicant factor in some sessions and that subtle difference in others.
The designer considers the reference to TNT (the explosive) might be a bit apropos too. Both share
a reputation as a relatively powerful and particularly useful tool for the ‘difcult’ tasks while being
relatively safe (well, much safer and more stable than Nitro-Glycerine, its main component). Manley
would like to thank Steve Pogact for suggesting the name.
Most mic preamps are stereo, which is ne when one needs to record true stereo with matched mics
(few are), but the most common situations where one can compare and choose a particular preamp,
are the often the more relaxed overdubs. These are typically single miked or multi-miked where each
mic might be a different type and different distance from the source. So the TNT might be the ideal
cost-effective solution for these situations – maximum choices & minimum cost and rack space and
where you need to know you are using the one of the best.
Some people use the TNT simply because it offers two different sounds and is different from their
other preamps. Some people choose it because each channel may be a contender for the highest
caliber preamp in either the “tube category” or “solid-state category” and they demand the best. And
some users just like the unique controls and features. Of course, given a variety of sounds and fea-
tures, different people will gravitate to one side or the other and one feature or another. This is to be
expected and probably encouraged, however let us emphasize that we encourage you to dig in, use it
to its fullest and form you own opinions and methods that work for you.
GENERAL NOTES
LOCATION & VENTILATION
The Manley TNT must be installed in a stable location with ample ventilation. It is recommended, if
this unit is rack mounted, that you allow enough clearance on the top of the unit such that a constant
ow of air can move through the ventilation holes. Airow is primarily through the back panel vents
and out through the top.
You should also not mount the TNT where there is likely to be strong magnetic elds such as directly
over or under power ampliers or large power consuming devices. The other gear’s fuse values tend
to give a hint of whether it draws major power and is likely to create a bigger magnetic eld. Magnet-
ic elds might cause a hum in the preamp and occasionally you may need to experiment with place-
ment in the rack to eliminate the hum. In most situations it should be quiet and trouble free.
WATER & MOISTURE
As with any electrical equipment, this equipment should not be used near water or moisture.
SERVICING
The user should not attempt to service this unit beyond that described in the owner’s manual. Refer all
servicing to your dealer or Manley Laboratories. The factory technicians are available for questions
by phone [phone], or [phone] or by email at <[email protected]>. Fill in your
warranty card! Check the manual - Your question is probably anticipated within these pages......
3

THE BACK PANEL
First connect all the cables, then turn on the power, wait 30 seconds, then have fun, as if we had to tell you....
1) POWER CONNECTOR. First verify the POWER SWITCH on the front panel is off (CCW). Use the power cable supplied with
your TNT. One end goes here and the other end goes to the wall outlet. You know all this.
2) VOLTAGE LABEL (ON SERIAL STICKER). Just check that it indicates the same voltage as is normal in your country. It should
be. If it says 120V and your country is 220V, then call your dealer up. If it says 120V and you expect 110 it should work ne.
3) FUSE. Unplug the power cable rst. The Fuse Cap needs a push then turn a quarter twist CCW to pull off. Fuses are meant to
“blow” when an electrical problem occurs and is essentially a safety device to prevent res, shocks and big repair bills. Only replace
it if it has “blown” and only with the same value and type (500mA slow-blow for 120V, 250mA slow-blow for 220V). A blown fuse
either looks blackened internally or the little wire inside looks broken. A blown fuse will prevent all the LEDS from lighting and will
prevent any power and audio.
4) TUBE CHANNEL XLR JACK INPUT. ( Left) Accepts balanced or unbalanced sources. The pin out is as follows: PIN 2 = Posi-
tive = Hot, PIN 3 = Negative = Low or ground, PIN 1 = Chassis Ground. Be sure that the PIN 3 is connected to the negative or ground
and not “open” or a 6dB loss or loss of signal will happen. This input is transformer coupled. Switching PHANTOM POWER on, puts
approximately 48 volts via 6.8k resistors (double regulated 46-47 vdc typical) on pins 2&3.
5) TUBE CHANNEL XLR JACK OUTPUT. (Channel One or Left) Transformer Balanced and Floating. Only for +4dBu pro levels.
The pin out is as above. NOTE: Inserting a 1/4” plug into the “UNBALANCED OUTPUT” jack disables this XLR output !
6) TUBE CHANNEL PHONE JACK OUTPUT. (Channel One or Left) Unbalanced output only. Factory set-up for +4dBu pro lev-
els and mono or 2 conductor plugs. NOTE: Inserting a 1/4” plug into this jack disables the XLR output because it switches the trans-
former out of the circuit to prevent any loading. This 1/4” output should be used if the goal is to record as clean and tight a low end as
possible from tubes. This jack also should be considered if the destination or cables present a difcult load for the XLR transformer
output (high capacitance from long cables, or low resistance from 600 ohm vintage gear or more transformers).
7) COOL CHANNEL XLR JACK INPUT. ( Left) Accepts balanced or unbalanced sources. The pin out is as follows: PIN 2 = Posi-
tive = Hot, PIN 3 = Negative = Low or ground, PIN 1 = Chassis Ground. Be sure that the PIN 3 is connected to the negative or ground
and not “open” or a 6dB loss or loss of signal will happen. This input is transformer coupled. Switching PHANTOM POWER on, puts
approximately 48 volts via 6.8k resistors (double regulated 46-47 vdc typical) on pins 2&3.
8) COOL CHANNEL XLR JACK OUTPUT. (Channel One or Left) Transformer Balanced and Floating. The pin out is as above.
The 1/4” jack has no effect on this XLR (both can be used at once) but the OUTPUT MODE switch should be properly set (gener-
ally +4 Balanced for maximum headroom) however it is worth mentioning that a transformer oating output is equally happy driving
balanced or unbalanced inputs. But we will remind you that most unbalanced inputs are designed for -10 levels so in order for TNT’s
levels and LEDs towork as designed, if the desination is -10 consumer level the switch should be set for “-10 unbalanced” (usually ;>)
9) COOL CHANNEL PHONE JACK OUTPUT. (Channel One or Left) Balanced or Unbalanced output so a 2way or 3way(stereo)
plug can be used. Factory set-up for +4dBu pro levels. This 1/4” output should be used if the goal is to record as clean and tight a low
end as possible (transformerless). This jack also should be considered if the destination or cables present a difcult load for the XLR
transformer output (high capacitance from long cables, or low resistance from 600 ohm vintage gear or more transformers). The OUT-
PUT MODE switch should be properly set (depending on the destination and wires) because these outputs do not use cross-coupled
op-amps and are designed to properly drive either balanced or unbalanced systems providing the switch is properly set.
10) OUTPUT MODE SWITCH. Sets both the output level and whether both the XLR and 1/4” jack are balanced or unbalanced.
Normally this switch should be in the “+4 BAL” or Center position. Some PRO gear may prefer the “+4 unbalanced” position but this
style of input is becoming increasingly rare, however because the TNT loses 6 dB of headroom in this mode, it can be used for crea-
tive “drive” cleverness. Similarly the “-10 UNBALANCED” mode loses another 6 dB of headroom when ‘mismatched’ in typical +4
balanced systems. However, this mode is more likely to nd service because a fair amount of semi-pro and consumer gear with RCA
jack inputs are compatible with this level and 1/4” plug to RCA plug adapters are very common.
4
SERIALNUMBER
+4UNBALANCED
+4 BAL
-10UNBALANCED
OUTPUT MODE
MANLEY LABORATORIES, INC
13880 MAGNOLIA AVE., CHINO, CA 91710
PHONE [phone] FAX[phone]
SERIAL NUMBER
FUSE 1A @ 117V
FUSE .5A @ 220V
www.manleylabs.com
+4UNBALANCED
CAUTION -RISK OF ELECTRIC SHOCK. DO
NOT OPEN. REFER SERVICING TO
CAUTION: RISK OF ELECTRIC SHOCK. DO
QUALIFIEDPERSONNEL ONLY
TRANSFORMER & XLR
DESIGNEDBY HUTCH
TNT
DOES NOT BYPASS
TRANSFORMER
ISOLATED
CHANNEL 2
OUTPUT
TRANSFORMERLESS
OUTPUT
OUTPUT
MIC MIC
N9512422
1
TRANSFORMERLESS
OUTPUT +4 UNBALANCED
OUTPUT
DESIGNED BY HUTCH
OUTPUT
TRANSFORMER & XLR
BYPASS
DOES NOT BYPASS
TRANSFORMER & XLR OUTPUT MODE
+4 UNBALANCED
+4 BAL
-10 UNBALANCED
MANLEY LABORATORIES INC.
TNT
www.manleylabs.com
N9512423
1 3 8 9 10 7 6 5 4 2

TNT
+22
+10
0L
SIG
OUTPUT
INPUT
POWER
ON
OFF
60s
70s
CLEAN
IRON
TRIMGAIN
INSTRUMENT
FILTER
60 Hz
120 Hz
FLAT
PHANTOM
PHASE
ON
OFF
180
0
TRIMGAIN
INSTRUMENT
3MEG
1MEG
300K
10K
2400
600
FILTER
80 Hz
FLAT
PHANTOM
PHASE
ON
OFF
180
0
IMPEDANCE Ω
20
25
30
35
40
45
50
55
60
65
70 20
25
30
35
40
45
50
55
60
65
70
2
3
0
-1
300c
300
600
2K
2M 10M
100K
300K
1M
3M
BY MANLEY LABS
IMPEDANCE Ω
TUBE
CHANNEL
COOL
CHANNEL
+6
+10-10
-4
0
-8
-6
-2
+8
+4
+2
P
B
+6
+10-10
-4
0
-8
-6
-2
+8
+4
+2
P
B
COLOR
P
B
P
B
1 3 8 10 15
2 4 5 6 7 9 11 12 13 14 16 17 18
5
THE FRONT PANEL
TUBE CHANNEL
1) PHANTOM POWER: Toggle up turns 48 volt phantom power on (and the amber LED) which is needed for most FET condensor
microphones. Turn your monitors down because it may make a big ‘POP’. Avoid patching the mic lines if phantom is turned on. Some
ribbon mics can be damaged if phantom is on and cables or patches are changed, so don’t use phantom with ribbons - or be careful. 2)
PHASE SWITCH: Reverses the polarity (180 degrees) of the microphone signal. Sometimes needed in situations where two mics are
used and sometimes useful for vocals when headphones are used. Red LED is ON when PHASE switch is engaged.
3) HIGH PASS FILTER: Toggle up engages a basic 80 Hz  lter, Used to remove excess lows, rumble and some air conditioning
noise.
4) IMPEDANCE SWITCH: 3 position toggle changes the loading characteristics presented to the microphone or instrument. This
can subtly change the sound of the mic. “2400” ohms is considered normal or typical. “10K” is a lighter load and may be appropriate
for some sounds and often for ribbon mics. “600” ohms may tighten up the lows on some mics. Unlike many Impedance switches, the
volume will not change by 6 dB, and will stay relatively constant making comparisons easier. The numbers to the right of the switch
indicate the impedance given on the 1/4” Instrument Input, where 1 Meg simulateds a typical amp. Higher usually means brighter.
5) INSTRUMENT INPUT: Plug your guitar or bass in here. A plug inserted in this jack will disable the XLR Microphone Input.
6) GAIN SWITCH: This rotary switch sets the gain for the  rst ampli cation stage. The steps range from +20 dB to +70 dB and
when used with the TRIM (below) provides a range of +10 to +80 dB of gain. The bottom two LEDs (see #17) indicate “signal pre-
sent” and “overload” of this  rst stage. If internal jumpers are properly set, one can turn this switch higher for overdrive and turn down
the GAIN TRIM to optimise the level again. If the jumpers are set for “clean” then it may be dif cult to overdrive this stage.
7) GAIN TRIM POT: This pot is typically used to  nely adjust the gain as needed for the recording device or converter. The two top
LEDs are associated with this knob, and are intended to help set optimal levels, which are well (about 10dB) below when the TNT
clips.
COOL CHANNEL
8) PHANTOM POWER: Toggle up turns 48 volt phantom power on (and the amber LED) which is needed for most FET condensor
microphones. Turn your monitors down because it may make a big ‘POP’. Avoid patching the mic lines if phantom is turned on. Some
ribbon mics can be damaged if phantom is on and cables or patches are changed, so don’t use phantom with ribbons - or be careful. 9)
PHASE SWITCH: Reverses the polarity (180 degrees) of the output signal.
10) HIGH PASS FILTER: Toggle middle position is a 120 Hz HP  lter, Toggle up engages a less drastic 60 Hz  lter.
11) IMPEDANCE SWITCH: This is a 5 position rotary switch that both controls the loading on a connected microphone and in-
ternally directs and shares the signal between two different preamp circuits or topologies. The least amount of loading is the 2 MEG
setting and the next setting marked 2K (2000 ohms) might be considered traditional or typical (most preamps were designed for 2000
to 3000 ohms). Both of these two only use the cascode FET preamp. The next two settings share both the cascode FET preamp and the
current mode preamp, 600 and 300. The  nal setting, 300C, only uses the current mode preamp and relays bypass the sub-circuit used
for mixing the preamps, so it has some purist function.
12) INSTRUMENT INPUT: Plug your guitar or bass in here. A plug inserted in this jack will disable the XLR Microphone Input.
13) GAIN SWITCH: This rotary switch sets the gain for the  rst ampli cation stage. The steps range from +20 dB to +70 dB and
when used with the TRIM (below) provides a range of +10 to +80 dB of gain. The bottom two LEDs (see #17) indicate “signal pre-
sent” and “overload” of this  rst stage. Use this switch in conjunction with the 60’s-70’s switch and the LEDs to control the amount of
color or distortion. In this situation the GAIN SWITCH becomes a “drive” control too.
14) GAIN TRIM POT: This pot is typically used to  nely adjust the gain as needed for the recording device or converter. The two
top LEDs are associated with this knob, and are intended to help set optimal levels, which are well (about 10dB) below when the TNT
clips.
15) COLOR SWITCH: With the switch in 60’s or 70’s, a circuit is added that is designed to clip in an interesting way that somewhat
simulates the way magnetic tape, and guitar amps clip. Use the GAIN SWITCH to control the depth of distortion. In general best
results are obtained when the desired effect is subtle and this circuit is just lightly driven and obvious distortion is minimal. Of course,
sometimes more drastic effects are desired and the GAIN SWITCH can be turned up. Thicker distortion may take several processors.
The 60’s - 70’s switch can alter the highs depending on drive levels.
16) IRON EFFECT: This knob adjusts how audible the output transformer may be from exagerated at +3 to near zero at 0 and even
becoming inverse or the opposite of a transformer at -1. This control is essentially “out-of-circuit” with the knob straight up (12:00)
(like an EQ). The knob controls several subtle effects including low frequency level, low frequency distortion, high frequency level
and high frequency dynamics. This control is often subtle and somewhat signal dependent.
17) LED LEVEL INDICATORS: Simple indicators to show signal presence,  rst stage clipping, and more or less appropriate levels
for the next device. See page 000 for more deatails.
18) POWER SWITCH: With this switch UP, LEDs should come on and maybe sounds might come out the back XLRs......

BEGINNINGS
The TNT project began due to requests from fans of
the SLAM! and in particular Lynn Fuston of 3D Au-
dio Inc. The request was simply “Can you bring out
just the SLAM! Mic preamps without the Limiters and
other features. Then came the 3D Audio bulletin board
“Dream Pre-Your ideas wanted” thread which had a
lot of great ideas and diverse opinions. Perhaps the
most obvious theme was that engineers were now us-
ing several mic preamps at their disposal for a variety
of colors like they had always done with mics. This
was actually a pretty new trend in ‘92. How about a
box with a few different preamp topologies for differ-
ent sounds?
We began to experiment with some simple discrete
preamp design concepts and breadboarded a few ap-
proaches. Hutch had also had developed the “Rapture”
gain stage intended for a proposed digital converter
that was impressively un-colored and which became
the standard against which other ‘experiments’ were
compared.
Then the 3D mic preamp summit “Preamps in Para-
dise” happened January 2004. This was a historic
event in Tennessee with a panel of 10 notable preamp
designers, and 7-10 famous engineers known with rep-
utations as preamp connoisseurs. Amongst fascinating
stories and a sharing of approaches, this designer was
hearing a chorus of requests, a short list that includ-
ed “variable impedance – but minus the typical gain
changes” and “some new useful control or knob”. Up
to then, the solid state preamp we were working on
was envisioned as a typical minimalist ‘2 knob’ dis-
crete channel in some ways similar to the tube side
borrowed from SLAM!. But the engineers were ask-
ing for more control, and were describing approaches
based on sonic characteristics such as clean / not so
clean, bright / not so bright, transformer or transfor-
merless and this resonated with the designer’s session
experience. Designers talk about discrete topologies,
tube types and transformer details but recording engi-
neers talk about sounds and controls and session tech-
niques.
The initial concept of the TNT was to put two very dif-
ferent mic preamp technologies in the same box, and
that each were to be as simple as “plug in a mic and
it sounds ne”, without a lot of controls to get in the
way. In the end, the TNT did get new features and con-
trols such as the IRON knob, 60’s - 70’s switch and its
unique impedance control. And these were largely due
to engineer’s requests from the “Preamps in Paradise”
event.
At the 3D Preamp Summit, the topic of “vintage-
style” electronics came up, not because of huge de-
sire from the engineers but more as a designer topic
relating the headaches of recreating transformers and
obsolete parts accurate enough to be comparable to
the original. However where there was interest in old
school style was when the recording engineers began
to talk about how they did those classic 60’s sessions,
and the focus was on production technique and war
stories rather than components and gear. Maybe the
engineers were saturated with recreations of old gear
and were craving both the magic of old sessions and
yet new exciting toys to do their job with tomorrow.
A bit of both.
So we went back to the ol’ drawing board and back
to the lab bench and experimented with a variety of
circuits and topologies, but this time holding truer to
the end result the user would appreciate rather than the
internal workings that might have buzz word appeal.
Already the SLAM! preamp was not “all-tube” but
more of a hybrid FET-Tube cascode, so why stick to
“all-discrete” or “vintage-clone” when the engineers
seemed to be just concerned with sound or tone and
occasionally hoped they could get a few new controls
if possible.
The TNT solid state side evolved into a mix of dis-
crete, and op-amps plus it ended up with the Rapture
Amp for the line driver. Why this mix? Just our choice
based on listening comparisons where our choices
generally favored the cleaner or most true to the source
as a base. The users could always add stuff that gave
some color or texture onto that base and we provided
a few too.
We did come up with a few controls that gave some
possibilities for “tints” or “avors” that could be di-
aled in. For the most part these were designed to be
subtle rather than drastic because the TNT is a mic
preamp and not an EQ or a typical processor. In fact
even the IMPEDANCE switches were designed to not
mangle the sound in unintended ways - they should
be “just” impedance controls without baggage. Some
users may expect bigger sonic changes from huge im-
pedance changes or major audible effects from vary-
ing the IRON content, but the folklore surrounding
those ideas is maybe more dramatic than reality. These
controls were designed to reect reality which seemed
appropriate on a high end Mic Pre and tend to be more
like tweaks and trims. And this was more in-line with
the original concept of a basic good plug in a mic and
go preamp.
6

The TNT was getting interesting. We now had a tube
preamp from the SLAM! on one side plus two solid
state preamps working together on the other side, and
each of those 3 circuits had a unique sound or subtle
avor yet there was some common theme or style.
The tube channel is based on a JFET / Vacuum Tube
Triode cascode circuit that is quite unusual in that it
is a blend of old and new components. The cascoded
combination allows for high gain, low noise and low
distortion without using negative feedback.
On the solid state channel, one of the preamps also
uses JFETs in a cascode topology. The high imped-
ance circuit operates in the voltage mode. The ideal
voltage amplier would have innite input impedance
and the current ow would be zero. We use a paral-
leled cascaded ultra-low-noise FET / op-amp circuits
and the TNT requires a pair of those hybrids for bal-
ancing (8 discrete matched FETs). There are a few
interesting twists here too. When phantom power is
engaged, it uses the conventional 6.8 k-ohm phantom
power resistors plus the usual DC blocking capaci-
tors. So even if the impedance switch is set to 2 Meg
Ohms, the phantom circuit limits the impedance down
to about 14 kohms. But if phantom is turned off, TNT
removes those resistors (rather than switching them to
ground, as is standard procedure) and bypasses the DC
blocking caps, so that you truly have 2 meg input im-
pedance and DC coupling restored. And no free lunch
here either. Compared to the current mode amplier,
the voltage mode amplier typically tends to have
opposite characteristics in terms of its strengths and
weaknesses.
The low impedance circuit is based on a special Lun-
dahl transformer designed to operate in the current
mode. This allows the transformer to work down to
near DC yet be very small physically. This was paired
with an ultra-low noise, ultra-low distortion op-amp
that won in our listening tests.
By combining the JFET and Current mode preamps
we were able to create a variable impedance that
uniquely sensed and amplied both voltage and cur-
rent. And this in turn provided much better gain con-
sistancy while usually sounding a bit better than ei-
ther approach alone. In other words the volume didn’t
jump or shift as the impedance control was changed
unlike most (or all) other approaches. Some switch
transformer taps, but transformer frequency response
is very source dependent. And some preamps had 20
dB gain changes as the impedance knob was adjusted.
Now that users can accurately hear and compare the ef-
fect of variable impedance without huge gain changes
and without signicant frequency response changes,
it becomes truly interesting to hear what effects there
are. In most cases these effects are not life changing.
Even where low impedance settings seem to affect the
damping or tightness a dynamic or ribbon mic might
exhibit, one then may be faced with an unfamiliar
sound from a familiar mic. This may be a good thing
sometimes, but often one picks a familiar mic for its
familiar sound. And one may hear similarly question-
able highs in the high impedance settings. One might
hear excess sibilance or harshness that may be due
more to cables and cable distance than anything else.
In the end, one may be most comfortable with the two
middle settings of 600 and 2400 as the idea of extreme
impedances gradually lose appeal.
Maybe the TNT might be viewed as a bit of a myth-
buster in regards to “variable impedance”. Yes, it is
sometimes useful - but can often be subtle - not ex-
actly the most important feature for a mic preamp.
And then the basic premise of a tube preamp and solid
state preamp being very different sounding animals
might be a myth too. At one time we had both preamps
tuned and adjusted to be extremely clean and transpar-
ent. One might guess that two transparent gain stages
regardless of the technologies might sound the same,
which was essentially inaudible. We had to go back-
ward and re-introduce some of the “aws” to recreate
some of the creative differences that we all expected.
We added some internal jumpers that essentially un-
trim the tube bias trimmer pots that are tweaked to set
up minimum distortion.
Same thing with the IRON control..... So much has
been said about the sound of transformers lately that
many people expect that one component to almost
be responsible for every products signature sound -
wrong ! Sorry another myth. Most modern transform-
ers are pretty transparent when used properly.
In fact, we had to use several techniques just to make
the IRON control ‘audible’ including designing the
transformer with unusually low permeability lamina-
tions, driving it with a non-optimum source, and forc-
ing DC into a tertiary winding to create more distor-
tions. In other words it was a bit of a ght to make it
audible enough to wrap a control circuit around it.
7

Perhaps it is because those near opposite characters of
the two circuits, that when combined or blended the
audible benets and strengths of each prevail, while
the weaknesses of each are minimized. Of course, the
better each circuit is optimized, the closer they tend
to meet in the middle (transparency). Perhaps it is
because the approach of respecting both voltage and
current, it results in a form of optimal power transfer.
Optimal power transfer is a very old topic in electron-
ics and it relates to the old 600 ohm impedances pro
audio inherited from the telephone industry and the
75 ohm terminations we need to be concerned with
for word clock and video lines. Maybe with complex
sources, there is valuable information carried both in
voltage and in current and maybe most mic pre inputs
are not as simple as a basic resistor. In other words, to
some degree a typical microphone is a complex source
(especially dynamic, ribbon and transformer coupled
condensor mics) and a typical mic preamp input may
also be a complex load (especially if it is transformer
coupled) and the cable and connections between the
two might also be viewed as a combination of resist-
ance, capacitance, inductance and distance. So maybe
it is all too complex to grasp without some serious
computer modelling, but maybe it can be easy enough
just to hear in some situations - and we’’ll leave that
up to you.
We would like to speculate that one of the complexi-
ties that you might experience will be cable length.
While we were designing the TNT we noticed excess
high frequency sibilence coming in at the highest im-
pedance settings. We nally traced it to the mic ca-
bles that we were using. If we doubled the length, the
problem doubled and if we used a very short cable the
problem disappeared. And the problem wasn’t appar-
ent at low impedance settings. OK but why? Here is
where we have to speculate.
At low Z settings, it may be akin to our old 600 ohm
terminated lines that pro audio inherited from the tele-
phone industry. And that standard was set up to reduce
echoes in early long distance lines. It also resembles
the 50 ohm or 75 ohm terminated lines used for video
and word clock where cable reections impact high
frequencies. Normally we don’t consider audio fre-
quency cable reections to be a concern because they
don’t seem to affect the 20 kHz frequency response
or square waves on our ‘scopes. So our speculation
might be a question. How far do these cable reections
need to decay (in dBs given that -60 dB is 1/1000) be-
fore they do not intersect with our abilities to perceive
transients? Or how many microseconds of reections
and down to what dB? Just use a shorter cable.
Impedance Issues and Microphones
OK, the above might be a bit of technical mumbo-
jumbo and what you really want to know is what to
expect and listen for when you change the impedance
switch in your session. Simply, at very high impedance
settings, there are usually a little more highs. At low
impedance settings, with dynamic and ribbon mics
the bottom often tightens up. In the middle impedance
settings, the preamp may sound closest to what you
have grown to expect with that mic because most mic
preamps are medium impedance and typically 1000 –
3000 ohms.
With high impedance settings, one may be affecting
the mic and cable in a few ways. First, with trans-
former coupled mics like most dynamic, ribbon and
tube condenser mics, one might be setting up a high
frequency peak in the mic’s transformer that may have
been intended for 1 kohm to 3 kohm preamp imped-
ances. The opposite is also common, where very low
impedances may cause the transformer to roll-off
highs earlier than the designer intended (yeah, but
its your mic and your session, so choose the setting
with your ears). The other effect, goes back to that
rambling about cables and time domain effects. Listen
carefully for excessive sibilance and what might be
described as an articial harshness, and what perhaps
the most nely honed ears will hear as time-smearing
in the top octaves. This effect is directly related to
cable type and length, and once you lock into it, you
can prove it by doubling (or halving) the cable length.
Even better is moving the TNT into the studio once
you have your settings, and using a 4 to 8 foot cable
from the mic to the preamp. It seems puny low level
mic signals are more fragile to these effects than hot-
ter line level (and robust line driver driven) signals but
we don’t know why. Give it a try. If this seems a bit
inconvenient for level tweaks, add a simple passive
variable attenuator (fader or pot) in the control room
near your converter (if it has inconvenient input level
adjustments) if you are a purist, or use the compressor
or EQ gain controls, if you’re not. The TNT has quite
a bit of headroom (except in 60’s / 70’s mode) so there
won’t be much chance of overloading it and the real
thing to keep an eagle eye on is the analog to digital
converter at the end of the chain
Away from the extremes, the 2K (2000 ohms) set-
ting represents the standard impedance of most mic
preamps and what most microphones are designed to
drive. In other words, its safe, and maybe a bit ‘va-
nilla’ and this isn’t a bad thing. The 600 ohm setting
is also pretty safe and may have some advantages be-
cause it gets closer to a 50/50 blend of voltage and
current mode preamps.
8

At very low impedance settings with dynamic and rib-
bon mics another effect can come into play. Damping
is a term normally associated with speakers that refers
to the fact that a dynamic speaker comes to rest faster
and is better controlled when connected to a very low
impedance amp. (It was one of the biggest selling-
point features when early solid-state amps with tons of
negative feedback rst came out.) Damping often has
a dramatic effect on a speaker’s frequency response
and is one reason why some speakers work better with
solid state and some better with tube amps (they were
designed to, or what they were designed with). A simi-
lar effect often happens with dynamic mics and the
bottom tightens up at low impedances. Whether this is
desirable tends to depend on whether you are aiming
for a tight and probably ‘truer-to-the-source’ sound or
the sound of the mic that you and the world is more
familiar with and might be viewed as more authentic
or traditional. You might even use the tight 300 ohm
settings for tubby instruments and the 2K setting for
drier sources and mics.
To complicate matters further, it depends on the mic.
Modern FET condenser direct coupled (transformer-
less) mics are mostly immune to whatever setting im-
pedance you select, (though you might isolate some
of those cable and preamp circuit effects described
above) so expect generally very subtle or negligible
differences. At worst, with loud sources and lowest
impedances you might introduce early clipping with
the occasional FET condenser mic. Tube condenser
mics are fairly immune but the impedance may affect
the frequency response of the transformer. And with
ribbon mics, one concern might be getting enough
highs to start with, so you might want to especially
watch out for losing highs while you focus on the
tighter bottom with low impedances. But the good
news is that ribbon mics tend to be famously forgiving
when boosting the highs with a good EQ so it may be
easy to “get the cake and eat it” this time.
And for those who just don’t want to be bogged down
by any technical issues and complications: you are in
luck again – just turn the knob and pick the setting
that sounds best for this track. In fact, this is the best
advice for those that love all the technical explana-
tions too, and when you get down to the session, the
most important thing is to listen and choose based on
the heart and the tapping foot rather than the intellect
and some words in a manual or web-site. Remember
the music, remember to listen. The old adage remains
valid “If it sounds good, it is good”.
We touched on using the impedance switch by ear
and how the low impedance settings may be tighter
in the lows, the medium impedance settings might be
the ticket for the advantages of blended preamp those
settings represent typical mic pre impedances and how
the highest impedance may be useful for squeezing the
last drop of highs (but not necessarily the most accu-
rate highs).
One way (not the only way) to approach the IMPED-
ANCE switch is to begin at the middle or “600” set-
ting. Listen to what you get. If the sound strikes you
as OK but already a bit bright, then try the lower im-
pedance settings. If your rst impression is that this
instrument/mic sounds good but a little dark, then try
the higher settings. Quite likely, your rst impression
is that it won’t sound exactly OK or good enough, so
the best advice, is that you should be really be out in
the studio adjusting the mic position and you are not
at a point where the subtle effects of adjusting preamp
impedance will help enough. Maybe you started off on
the wrong foot, or wrong mic in this case. You might
try approaching mics the same way as the IMPED-
ANCE switch. If the instrument is hard sounding, try
a softer sounding mic, and vice versa. When you have
a bright stinging instrument, maybe you don’t want
to use the brightest mic in the brightest position and
coupled to a bright preamp in its brightest setting, fol-
lowed with EQ in maximum “air” settings. The real
trick to getting “air” is letting that track and the others
to “breathe”, give it some room to move, rather than
add some electronic artifacts. It doesn’t take Einstein
to suggest sounds or tones in a song are “relative” (and
so is volume).
A proven approach, is rst to listen to the instrument in
the studio, walking around, getting a handle on where
it sounds best and how the tone changes around the
instrument. We do that because instrumental projec-
tion isn’t necessarily obvious and because it gives you
a starting point and the information needed to tweak
mic positions. Then one might choose a microphone
or 3 and maybe based on complementary character-
istics. We might also suggest experimenting with mic
positions by ear rather than by the eyes, or ego. One
might say the rst task of an engineer is re-creating the
sound that the musician is hearing and intended. The
second task might be understanding the musician in-
tended it to sound better than what he got in the room
and that maybe something larger than life (as opposed
to squashed and smaller) might be what the sound be-
comes in the mix. Some of you laugh and say “Not my
clients, not my mixes!” One can hope.
9

The Tube Channel
The left side (T) or channel one, is almost an exact rep-
lica of the SLAM! Mic Preamplier and audio path.
The only differences are the addition of the Imped-
ance switch and an additional shunt regulator on the
phantom power. The latter reduces noise and provides
a softer-start & off with the phantom power switch-
ing – less thump and less chance of input transformer
magnetization.
After being introduced, the SLAM! Immediately de-
veloped a reputation as one of the best and easiest to
use tube mic pres. It seems to particularly shine on
the traditionally most difcult sources like sax, brass,
raspy vocals and most percussion. It might not be the
rst choice for those looking for a dramatically color-
ed preamp or those looking for gobs of tube-warmth
(distortion) and it isn’t a one-trick-pony that stamps
its own personality on every sound. However, it does
have both an input transformer (Lundahl) and output
transformer (the one we developed for the SLAM!)
and it does have two stages using tubes and it is true
class-A from input to output, so yeah, it does have
some character and tube-magic, and a tasteful amount
of warmth. In other words, clean but not sterile, and
it is neither avor-less nor overbearing. Perhaps, the
simplest description from a reviewer both describes
this tube preamp’s ‘sound’ and the designer’s actual
intention – “Just plug in a mic and it sounds great”.
There are twin tube gain stages based on one of most
rave-reviewed hi- phono preamps ever, “the Man-
ley Steelhead”. These gain stages can be described
as JFET-Tube cascode ampliers. The FET is the rst
stage to keep the noise oor low, and the tube pro-
vides the bulk of the voltage gain. The beauty is that
the FET and tube are so arranged to cancel the distor-
tion of the other (complementary). The topology and
balancing of this circuit has such low distortion that
there is no need for negative feedback, (which might
be appreciated by audiophiles). The circuit is also set
up to compensate for both FET and tube variations
and their drift.
This preamp also tends to have a great deal of head-
room in most situations. While one can push the rst
stage hard to get some clipping when desired, one re-
ally has to try hard – this preamp wasn’t designed to
be an expensive fuzz-box. On the other hand, this is
why it tends to work so well with difcult complex-
wave sources and why it succeeds as a “plug the mic
in and hit record” preamp.
Are there any tricks to using it, anything in particular
to be concerned about or suggestions about its care
and feeding? Practically none. Set the GAIN TRIM
knob to near the middle or straight up as a starting
point, turn the monitors down when plugging in a mic
cable or switching phantom on or off (as usual), ad-
just the GAIN rotary switch to get an good level, hit
record. The 4 LEDs on the far right are intended as a
rough starting point to set that “good level” but there
is ample headroom and low noise in the preamp that
the LEDs mostly serve as ‘signal present’ and ‘over-
load indicators’.
The IMPEDANCE switch can be set to taste. Prob-
ably the 4K setting may be the brightest or hardest,
and the 600 setting the softest or phat-est. It affects the
instrument ¼” jack that way too when fed by magnetic
pick-ups. It probably won’t have any effect on guitars
or basses that have internal preamps, or after pedals,
and probably no effect on synths. And on that note,
before you write off a mono preamp as a last resort
for synths because they all have stereo outputs – usu-
ally you can plug into just its left output and get the
full sound, save a track, and not be semi-forced into
yet another wide spread left-right synth sound. In the
mix, give it a position, and add some good convolu-
tion reverb (especially authentic rooms), and maybe it
will begin to resemble a real-life instrument and not a
‘stereo-type’ wash.
There are two outputs, a balanced XLR and an unbal-
anced ¼” jack. They sound a bit different and you can
get a little variation of tone that way too. The XLR
has a transformer in the path so it may sound a little
“warmer”, softer, rounder and fatter, more ‘vintage’
or ‘classic’. The ¼” output interrupts the feed to the
transformer and the XLR, and sonically it might be
called a hair brighter, harder, more transparent, or ac-
curate, depending on who is trying to describe subtle
little details in sounds, what aspect they are focusing
on and what instrument is being fed through it. Of
course life is never quite that simple, there is a vari-
able that can affect the XLR output and cause all the
above generalizations to be thrown out the window.
Transformers are dependant on the load. For example,
if there is appreciable capacitance in the cable because
it is a few hundred feet long, it’ll probably cause some
high frequency resonance (a few dB boost). label it or
dening hard and fast rules for recording music (other
than to impress your clients, of course).
10

Tube Channel Continued
If the transformer is driving some heavy resistive
load like some piece of vintage gear still set up for
600 ohms then you can expect some high frequency
roll-off and maybe a shift in the distortion and clip-
ping towards the tubes and away from the transformer.
Maybe the best approach, is just to listen and compare,
pick the best sounding output for this track, and don’t
worry about trying to label it or dening hard and fast
rules for recording music (other than to impress your
clients, of course).
Tubes will need to be replaced occasionally. Some-
times they last a few months, sometimes 30 or 40
years so about the only thing we can tell you is re-
place them when they get noisy, microphonic or the
preamp stops passing signal. Generally, there won’t be
a major advantage with new tubes, broken in tubes, or
esoteric and rare expensive tubes and in fact any of
these might be worse. Here is the thing – there are 2
trims for the 2 JFET-Tube stages that adjust the bias
and thus set the distortion null point. Inserting a fresh
tube might require adjusting both of those trims, and
that really should be done by a technician with a dis-
tortion meter for the best results. And there are anoth-
er two trimmers that are “ne gain adjustments” for
each stage, and while less critical, should be tweaked
with fresh tubes. In other words, the performance of
this preamp is equally dependent on the tubes and the
trimmer tweaks, and the tweaks are there to get ideal
performance from a variety of tubes and compensate
for drift in a tube over decades. The JFETS used as
the rst stage relax the requirements for a super-low-
noise, low-microphonic, expensive esoteric tube and
allow those pesky trimmers that should optimize for a
good variety of 12AX7A’s.
So the preceding paragraph was aimed at those who
like to buy $300 tubes on ebay, and that’s OK, but most
of us (and Manley Labs) tend to just use the $15 to $30
ones and get as good performance because we follow
the procedures. And those who just need to change a
12AX7A and don’t have access to a distortion meter
or don’t have the time, generally, it will work just ne
and the difference between tweaked-out and not, will
be negligible – You see, the circuits are also set up to
self-adjust to a large degree, so you can sweat the de-
tails or not, and usually be OK. And changing tubes is
almost as easy as changing a light bulb, about as easy
as changing a 9 volt battery in stomp-box and a whole
lot easier than changing a transistor or chip, especially
if its surface-mount. Your grandfather probably xed
the family TV any number of times. Relax.
About the only other “tricks” we might add here are
more general and apply to most preamps and not just
the TNT. Avoid plugging in mics, cables, mic patches,
etc when phantom power is turned on (and especial-
ly if the monitors are up). What can and often does
happen is that one “leg” of the balanced line (Pin 2
or Pin 3) connects rst, which can put a spike of 48
volts through a transformer and magnetize it. This has
been known to damage ribbon mics and there are usu-
ally transformers in ribbon mics, dynamic mics, many
condenser mics and of course many preamps, the TNT
Tube side included. There are some engineers that like
to demagnetize input transformers on preamps before
big sessions. Probably a small, weak cassette tape-head
demagnetizer won’t be too effective because virtually
all mic pre input transformers are mu-metal shielded,
but the bigger pro head de-magnetizers, carefully and
slowly brought near and away from the transformer
is probably a good thing to do as yearly maintenance.
One might also feed in a strong (say +25 dB) low fre-
quency tone and slowly decrease its level to zero once
in a while and get similar benets. As far as those dy-
namic and ribbon mics and their transformers, best not
to try because they also need those permanent magnets
(in the capsules). It might be worth checking with the
manufacturer on transformer coupled condenser mics,
but probably they would rather you not take a chance
or risk breaking something. So lets repeat, avoid plug-
ging in mics, mic patches etc with phantom on so that
you never have to worry about it. And lets also take
the devil’s advocate point of view to balance the issue.
Originally phantom power was called “phantom” for a
reason and most consoles of the 70’s and 80’s (before
external mic pres) didn’t have an on-off switch for
phantom power, per channel or even global – it was
always on. For 99% of us who were there, we always
turned down monitors when changing mics, and we
didn’t think to de-mag anything except tape heads and
we occasionally made great sounding records. Back
then, we weren’t looking for ‘air’, ‘warmth’ or ‘loud’,
we were just having fun capturing rst takes, hope-
fully exciting performances, and experimenting with
mic choice and positions.
A real good trick with mic preamps, console channels,
etc that isn’t mentioned nearly enough has to do with
the PHASE switch. It is relevant here because we ex-
pect the TNT will often be a rst choice for vocals and
many simple overdubs. In a single mic situation, you
in the control room probably won’t be able to hear any
difference with the phase switch in one position or the
other so you might write it off as insignicant.
11

Consider the singer, headphones on, and getting a
blend of their voice through bone conduction and
those phones. All too often there is something in the
chain with a polarity problem and it is usually a vin-
tage mic or the headphones but can also be caused by
a wiring mistake or a power amp. Did you ever get one
of those vocalists that continually complained about
her voice in the cans? Did you try ipping the phase?
One way will be thin and weird and the other will be
hopefully better, but only the person in front of the
mic can say. Might be worth singing into the mic your-
self, phones on, before the session while somebody in
the control room ips the switch for you. And while
you’re there, check out that headphone mix and level,
and the room temperature and creature comforts. This
will give you a bit more chance to work with the talent
in the beginning of the session -to also see if there is
some choice reverb in the phones that helps her per-
form and hit those notes. Either that or spend more
time auto-tuning later. These ‘tricks’ are not only lim-
ited to vocal sessions because a lot of times, the talent
is hearing a blend between the live room sound and
the headphone feed, but the benets of good sound in
the talent’s phones can be subtle, if you as the engi-
neer are focused on the ‘sounds’ in the control room,
because the benets tend to be in the performances.
One might also consider that one’s skills as an engi-
neer is often more related to the performances and hit
records that they have been ‘lucky’ enough to record,
than how great the mix was. Makes one wonder about
little things like phase switches, and using gear versus
choosing gear.
As a matter of fact, one can view the TNT as a single
piece of relatively simple gear that offers a fair number
of tints to explore and use. But that is the key! One has
to really dig in and explore the options and approach it
like an instrument with many possibilities. Though it
may be just another preamp that you try for 1 minute
and see if it delivers a sound that you like, it should
be approached as an instrument that needs some time
to learn. After all there is a variety of settings on the
Tube Channel, another bunch of settings to explore on
the Cool Channel and maybe the sound that you are
looking for is really there with a little coaxing in mic
choice and positioning choice and maybe even some
coaching of the talent to get that sound. Maybe one of
the biggest tricks that we can share is that it isn’t just
the gear, it is how one uses it. And before that, it is
about the source, the musician, the music and the in-
strument and the room, and you working with all those
factors before going crazy with choosing between 8
different preamps. The preamp does represent many
tints, but not prime colors.
More “Techniques” from other sources
For a really great source of tricks and techniques like
these, there are too few books. An Australian engineer,
who worked at Air Studios with Sir George Martin and
even has a forward by him, has written one of the best
books. The author is Michael Paul Stavrou and it is
called “Mixing with your Mind”
www.mixingwithyourmind.com, (Flux Research Pty
Ltd, P.O. Box 397, Mosman NSW 2088 Australia)
The inspiring part is that much of his focus deals with
the counter-intuitive and non-geeky approaches that
were learned the hard way through 20+ years of ex-
perience. For those struggling with technology, it may
suggest that some fresh techniques that reduce techno-
dependence, and for those that “just go for it” it may
enlighten them to very practical acoustic and signal
ow thoughts explained in easy visual metaphors. You
may be approaching the task of recording in one way,
and this book can pull you into a completely opposite
alternative, which of course lets you then roam that en-
tire space between your preconceptions and his. And
because it really is difcult to describe sounds in ways
that everybody understands, some of the labels and
categorizations tend to be personalized and this makes
for a great read.
Beyond that, it helps to know that “Stav” tends to be
a brilliant recordist who truly gets results on tape that
most of us would be jealous of - so he knows and has
taken the time to share in print - very rare.
On the other hand, we might suggest avoiding the dry
technical literature that seems to be the majority of
the recent texts on recording technology. Those might
be handy if you can make a living debating math mi-
nutiae or you are curious about those chips in the box
you bought. However most of them are almost useless
for both the recording engineer and the gear designers,
and often cloud the real issues rather than help. When
it comes to audio engineering, it mostly comes down
to the ears and making tasteful decisions. It may be
more an art than a science. It is not “paint-by-num-
bers”.
The point is this: If you are hungry for knowledge and
you search books and bulletin boards and magazines,
it all helps. What helps most is advice from guys do-
ing what you want to do and are experienced in deeply
and (importantly) are getting obviously good sound-
ing results. Artistic mentorship is at least as valuable
as it ever was, and is a huge advantage if you can get
it.
12

THE COOL CHANNEL
Solid State or Right Channel
The No Tubes side of the TNT gives you a range of
colors and might even be considered a contrast to the
Tube side. Or maybe not - If one has strong ideas that
tubes and transistors sound vastly different then the
TNT might be a little unsettling. For what it is worth
both the Tube side and Solid State side of the TNT are
pretty clean representatives of their technologies.
On the other hand it is extremely easy to nd a variety
of “personality preamps” using tubes (we make a few
too) that all sound different from each other. Similarly
there are many different solid state or discrete sounds.
It largely depends on topologies, parts choice (espe-
cially transformers) and a variety of other choices a
desinger might make (or a cloner might copy).
As a “clean” preamp (CLEAN setting and IRON
set fully counter-clockwise) we think the TNT Cool
Channel may be hard to beat for sheer transparency
and lack of electronic artifacts, especially in the 300
and 600 ohm impedance settings. It is also designed
to be useful as a fuzz-box or distortion device (60’s
or 70’s setting, INPUT GAIN hot, GAIN TRIM fully
counter-clockwise. It won’t simulate a Marshall stack
or analog tape with VU’s buried deep in the red but it
shares some of those characteristics and might be an
alternative sound and at least sounds better than most
preamps driven hard. Or it can give you a range of
subtle avors just as a basic preamp with the IMPED-
ANCE and IRON knobs, and/ or by using the 60’s &
70’s settings but driven lightly and before obvious dis-
tortion. These colors are set up to be easy and obvious
to use, even though they are for the most part subtle. In
fact, considering that this is really just a Mic Pre, and
not a compressor or EQ, it seemed most appropriate to
not go overboard and make it into an full blown proces-
sor, but rather give the user more control than is usual
yet keeping it within a ‘safe’ realm where it is unlikely
one will screw up a recording doing something that
can’t be un-done. That ‘subtlety’ might be obvious in
the IMPEDANCE switch, that unlike other preamps
that may have a 6 dB gain change from one setting
to the next, and again, the TNT is designed to have
maybe one dB of gain change from one extreme to the
other, with most mics. We consider this important for
selecting which impedance to use. Alternatively, com-
paring settings with radically different volumes makes
the process near impossible to do especially when the
differences tend to be subtle.
The IRON control may also be subtle in many situ-
ations because it uses the actual output transformer
(which starts off pretty good) rather than a fake simu-
lation just labeled to suggest a sound. The IRON con-
trol practically removes all audible effects of the real
output transformer in the “0” setting and that can be
easily veried by comparing the ¼” transformerless
output to the XLR transformer output.
Just a little note on the subtleties of the Impedance and
Iron controls: Maybe other units have more dramatic
changes when you adjust similarly labeled controls
and maybe what you are hearing then is aws in the
implementations or parts they use. We try not to do
that, and we won’t con you and we did put some ef-
fort into maintaining constant levels as these controls
are adjusted. We also try to maintain similar frequency
responses when impedance is changed, where others
don’t. So the TNT knobs do what they say they do, and
don’t add strange misleading effects (for a change).
The NT preamp starts as 3 gain stages. 2 are identical
and symmetrically used for opposite phases (XLR pin
2 and pin 3, ie; balanced) and are voltage ampliers
like 99% of all mic preamps. Unlike 99%, these volt-
age ampliers are very high impedance (2 meg ohms)
and exhibit very low capacitance and inductance, not
that microphones need or are designed for that light
of a load, but occasionally there are audible benets.
The third initial gain stage is a transformer input
current-mode amplier, which might be considered a
rare technology in a mic pre and nearly opposite to
the voltage amplier topologies. These 3 preamps are
variously selected and combined with the deceptively
simple IMPEDANCE switch. Rather than a resistor
that just shorts out the signal for lower Z, that resis-
tor feeds the current mode amplier in the TNT, and
the part of the signal that is normally thrown away is
amplied and mixed back in.
On the IMPEDANCE switch there are 5 positions.
Furthest counter-clockwise is the “300C” setting , and
next is the “300” setting. What is the difference? The
“300C” position is only the current mode preamp by
itself. The “300” setting uses both the current mode
and the voltage mode preamps and is closest to a good
50/50 blend. The next setting “600” restricts some of
the mic’s signal from going into the current stage and
more is available for the voltage stage, and the blend
is closer to 30/70. The 2000 ohm setting and the 2 meg
settings only use the voltage preamp.
13

The Impedance switch also has markings on the right
hand side that are for the INSTRUMENT input only.
How a magnetic pick-up reacts somewhat depends
on the impedance it is driving. This effect is diluted
because most guitars and basses have those volume
and tone controls that pretty much set the maximum
impedance the pickup will ‘see’. The pickups also
have to drive a length of cable, which often has ap-
preciable capacitance and may roll off some highs.
A fun trick for a session instrument is to bypass the
volume and tone controls (maybe on a switch??), just
leaving the pickup switch and jack, and then using
a fairly short low capacitance cable into a variable
impedance preamp like the TNT. In that situation the
IMPEDANCE switch becomes very dramatic and
the high impedance settings like “3 meg” and “10
meg” often get bright enough to sound much more
acoustic-like. Typical authentic guitar amp tones are
the 300K and 1 meg settings. The 100K setting may
be similar (thick and un-bright) whether the volume
control bypass mod is there or not. Guitars and basses
with “active pickups” (battery included) and gui-
tars feeding stomp boxes before the TNT, should be
mostly immune to the IMPEDANCE switch settings
and the 100K setting may have marginally less noise.
After the preamps are selected or are combined in
a very transparent summing amp, the next stage is
the “60’s / 70’s module” that contains a fairly simple
class-A all-discrete circuit, and is inserted when the
60’s or 70’s switch is selected, or relay-bypassed
when that switch is set to “CLEAN”. The module is
meant to simulate some of the qualities of vintage
discrete non-linearities, tape overload (what some
call tape compression), and changes the frequency
response slightly. It is not meant as a straight simula-
tion of any particular piece of vintage gear, and is
meant to evoke some general characteristics of those
eras and give the user a few more variations in the ol’
tool-kit. The 60’s/70’s switch also adds DC bias to
the output transformer to further simulate some old
technologies (and which can be further adjusted with
the IRON control). If sufcient interest is shown,
Manley may be able to offer alternative “modules”,
as this block is easily removed and replaced.
Then the signal hits the GAIN TRIM conductive
plastic pot, and is routed to the RAPTURE AMPS,
which are the nal line drivers in this preamp. It
drives the ¼” output directly and the output trans-
former (custom designed and manufactured in house
for the TNT) for the XLR output Two controls are
wrapped around the RAPTURE AMP.
One is the IRON knob, which compares the input
and output of the transformer, derives an error signal,
which is then sent to the IRON pot, that acts much
like an EQ boost/cut pot with zero ‘effect’ at 12:00 or
straight up. This way the user can reduce the effect
of the transformer to near inaudibility or exaggerate
it or just leave it as it is where this addional circuit
is essentially bypassed and the transformer output
is just pure conventional transformer and the ¼”
output is just clean and unaffected. In fact, if you use
the ¼” output and adjust the IRON control counter-
clockwise, you get an effect that might be called
“Anti-Iron” and could practically reduce the effect
of a transformer in the next piece of gear following
TNT, such as a compressor – kind of like “cleaner
than clean”.
The other circuit wrapped around the RAPTURE
AMP is the OUTPUT MODE switch on the back
panel. Rather than use the conventional cross-fed
feedback output that many use to make a balanced
output a bit fool-proof and simulate a transformer
and how it accommodates balanced and unbalanced
inputs, we have this switch. Why? For one thing, we
have the real transformer, for another, those circuits
are inherently usually within .5 dB of being called an
oscillator, and thirdly, the switch is 3 position, so we
can properly accommodate +4 unbalanced, +4 bal-
anced, and –10 unbalanced – all driven low imped-
ance, high current (full headroom down to 50 ohms)
and unconditionally stable. One might also note that
these two outputs are isolated and can serve to drive
two separate distant destinations easily.
The RAPTURE AMP itself was the result of months
of auditioning almost every discrete op-amp and gain
stage and every chip op-amp known to us to ever be
used for an audio product or published DIY project.
And we experimented with most of the tricks used to
further enhance all of these op-amps. In the end, we
found a circuit that was practically unique in its lack
of artifacts and sonic purity. After all those months of
R&D, it was decided that it should go in a block of
epoxy.
A similar routine of comparing the whole TNT
preamp to a lot of known expensive reference
preamps was performed while also continually
comparing the raw source to the preamps attenuated.
Lets just say we are condent that it is a winner and
particularly true to the source. Hope you like it!
14

Any particular tips using the NT channel?
Techniques specic to the solid-state side of the TNT
are not daunting. Most likely the rst thing to get your
attention will be the LED metering because it is a bit
unusual. The two bottom LEDs show the rst few
stages of the preamps or what is going on with the
stepped gain switch but BEFORE the Gain Trim knob.
The top two LEDs show that Gain Trim Knob and the
nal output.
The bottom GREEN LED shows “SIGNAL PRE-
SENT”. The RED LED above it shows when one
is beginning to distort the preamp or the 60’s - 70’s
circuit. So use this RED LED to help set how much
“OVERDRIVE” and a typical setting makes that LED
ash about 50% of the time - but trust your ears - too
much overdrive may be hazardous to ones career as an
engineer. You can’t undo mic pre distortion.
The top two LEDs are for the nal output and the
Green LED is intended to show a good level to your
converter and the RED LED is intended to indicate
probable A to D converter overload. Originally we had
that RED LED indicate when the Preamps began to
clip but they tended to stay dark, so now they just help
set a level for the next piece in the chain.
A good starting point for the 11 position GAIN switch
is “counter-clockwise” and the GAIN TRIM should be
set at roughly 12:00 or straight up. Turn up the GAIN
switch until you are getting a good level. You might
use the 4 LEDs on the TNT. The rst or bottom is a
“signal present indicator” and lights up about 20 dB
below optimum levels. The second from the bottom
LED shows clipping in the rst stages and follows the
GAIN switch but is before the GAIN TRIM pot. In
normal clean operation this LED shouldn’t light up
and is typically ‘skipped’. Where it will come in par-
ticularly handy is if you are operating the preamp to
deliberately over-drive it by turning down the GAIN
TRIM pot and turning up the GAIN switch. It should
be kept in mind that this won’t be easy in CLEAN
mode but it becomes quite easy in 60’s and 70’s modes.
An interesting sound is when that second LED is just
occasionally ashing in the 60’s/70’s modes, and the
distortion is subtle, and creates a psycho-acoustic ef-
fect of “character”, “richness” and a 3D effect.
When that LED is glowing steadily, the distortion
should pretty obvious. The LEDs are designed to ash
on both positive and negative peaks, and slowly fade. A
lot of peaks are too fast to see when the LED directly
displays peaks and the fade gives some clues to the du-
ration and musicality.
The top two LEDs are set to show output levels at the
output jacks. These are factory set up for +14 dB and
+20 dB over our standard +4 dBm so are technically at
+18 dBm and +24 dBm. Most A to D converters are
set up for +16, +18 or +20 so those two LEDs should
get you to a reasonable starting point and give you a
pretty good idea when clipping is likely. Of course,
you really do need to watch those A to D meters, or
tape machine VU meters as the nal judge, especially
when you have processing between the preamp and
recording device. However, if need be, there are inter-
nal trims for the LED thresholds, so one can set up the
LEDs for particular needs. It might be noted that there
is no LED to indicate when the TNT clips – because it
clips at over +30 dBm which is probably higher than
98% of the gear it might be driving. It seemed more
useful to indicate where the next device is likely to run
out of headroom, besides using the TNT for its own
overdrive effects is covered by LED #2.
If you tend to want the Cool Channel to be generally
your “clean preamp” and intend to use it as a reference
especially for acoustic instruments, then you might
want to consider using the 1/4” output as the main
output because the output transformer is not in that
path. And keeping it clean, you may want to leave the
“IRON” knob set at 12:00 or straight up. Turning the
knob either counter clockwise or clockwise introduces
some subtle transformer color. Now if there is another
transformer down the chain in another piece of gear
(or even a magnetic tape recorder), the counter clock-
wise settings may help minimize it’s contribution. You
might be able to use the 60’s - 70’s switch if you keep
the Input OL (overload) LED off by keeping the Gain
Switch lower and the Gain Trim higher or near its max
of +10 dB.
If you want the Cool Channel to be multi-tinted then
maybe the XLR output should be your choice. Then
experiment with all the preamp’s controls keeping in
mind that moving a microphone by a few inches might
affect the color more, maybe a different mic might be
more signicant a variation, and once you hit “record”
the player’s tone and volume usually change anyways.
15

Like most mic preamps, the TNT has high-pass l-
ters to remove unwanted low frequencies. The most
common situations to use it is for vocals to minimize
“pops”, wind noise and air conditioning rumble or
leakage, or for sounds that have little low frequency
information anyways, like acoustic guitar or high hats.
The basic idea is removing the garbage before it gets
recorded. You just might want to compare the effect of
a good analog high pass lter compared to the stand-
ard digital ones and also check out what happens when
both are used, from time to time. There are some engi-
neers that use a combination of a high pass lter and a
low frequency boost EQ, to get a tight fat bottom. For
that situation, we might suggest, auditioning the com-
bination but recording only the high pass lter, saving
the boost EQ for playback and rening in the mix.
There is a 3 way toggle labeled “CLEAN”, “70’s”,
“60’s”. The CLEAN setting has the TNT operate in
a standard clean mode. In fact, we probably could
have labeled it “damn stunningly clean” if there was
enough panel space. Tell tale things to listen for if you
want to compare clarity are ‘harshness in the highs’
‘smoothness and liquidity in the mids’ but also ‘snap
and punch’ and ‘dynamics in the deep lows’. It is hard
to overdrive this mode. We should point out, that for
“absolute clean” use the ¼” output, and the IRON
knob set to 1 (12 o-clock, straight up) to avoid any
transformer coloration. And “virtually absolute clean”
is using the XLR transformer output along with the
IRON knob set to –1 or fully counter-clockwise. This
method compensates for the transformer. Often the
300 setting on the IMPEDANCE switch sounds slight-
ly clearer as well. And while we are at it, if pure-clean
is the goal, choose your mic carefully, and avoid pro-
cessing or choose it extra carefully because it all adds
up, and nothing is perfect – in other words, maybe use
nothing, except a great passive ribbon mic, TNT and a
great converter running at 192K.
So if you are comparing preamps someday, your
natural tendency may be to set everything as at and
level as possible on each one, use the same mic and
try to judge which basic sound you prefer. If it seems
you tend to pick expensive transformerless discrete
preamps, the TNT should do well that way. Howev-
er if you tend to prefer color boxes, then maybe you
should be working with the TNT controls, setting up
modes and gains appropriately. Otherwise it would be
like comparing a several different cars without adjust-
ing the seats or mirrors. Even if the range of colors
isn’t drastic, one is still expected to adjust to taste.
While the CLEAN mode is a relay bypass of an ad-
ditional module, simply selecting “60’s” or “70’s”
engages this special module. It is a discrete class-A
circuit meant to simulate some of the stronger charac-
teristics of circuits and analog tape of those eras. The
most important thing that we must point out is that it is
purposely very level dependent and that it is between
the two gain controls so that the user can drive it as
hard or soft as they want to get a pretty wide variation
in tones. Driving it very lightly by keeping the GAIN
switch lower and the GAIN TRIM way up, mostly af-
fects the EQ and introduces a faster roll-off in the deep
lows and some shaping in the highs, so that there is a
subtle “presence” boost. Driving it a little harder is
particularly interesting and one begins to hear typical
vintage sounds including 3D depth, richness and edge
and a little further becomes a bit ballsy, aggressive and
forward. The trick is careful adjustments of those gain
controls and mic technique to land in the “sweet spot”.
This module can also be driven quite hard and be used
for some obvious dirt and you may nd that that the
character of the distortion is unlike most clipped
electronics and perhaps smoother, like analog tape or
a guitar amp. For the best overdriven guitar effects,
you may want to combine TNT with some good stomp
boxes driving into the instrument input, and some EQ
at the TNT output, and you might try feeding a real
speaker/room/mic or convolution reverb so that it
doesn’t end up too dry and clinical.
There isn’t much that can be said about the difference
between the 60’s and 70’s settings. “60’s” has subtler
shaping in the distortion and should sound brighter
when pushed hard. “70’s” uses more drastic shaping
and forces the output transformer to be biased, much
like some famous old British console electronics of
that period. One might say the “60’s” setting is more
like tubes and tape, and the “70’s” more like discrete
and transformer, depending how one associates tones.
In both cases, the distortion starts off mostly even or-
der and becomes more odd order as it is pushed harder.
Both tend to help get hotter levels due to softness of
the clipping character. Both are pretty easy to over-
drive and require care to avoid effects that cannot
be undone. Keep in mind, that usually an instrument
starts softer and gets louder during the song and dur-
ing the session and that our ears become less sensi-
tive & critical as the session wears on. When in doubt,
back down the GAIN switch one notch – better safe
than sorry.
16

The IRON knob may disappoint some who expect a
radical and obvious effect. It can be subtle, especially
for mid-range dominant sounds like vocals and gui-
tars because for the most part a transformer affects
the extreme lows, extreme highs and to some degree
the dynamics. This control is build around the actual
output transformer and lets face it, a good audio trans-
former shouldn’t be particularly colored and messy.
On the other hand, it has always been the transformers
in vintage gear that helped then sound warm, smooth
and round, yet were quite OK at passing audio pleas-
antly and without major damage. The IRON control
allows you to adjust the “Transformer Contribution”
from near zero audible effect, through to “typical” at
12:00, and further to where the effect is exaggerated
and practically tripled, which by the way, is still not
always obvious.
At very low frequencies a transformer can be said to
have 3 signicant effects: 1) it rolls off the subsonic
frequencies starting around 10 Hz, which is audible
due to the phase shift that happens mostly below 50
Hz, which acts to slightly delay the extreme lows. 2)
Hysteresis shapes the waveform for low level, low
frequency signals, putting a couple of bends around
the zero-crossing, which simply adds harmonics. 3)
Hot low frequency signals, can cause the transformer
to saturate or overload, again causing harmonics, and
may cause earlier roll-off, and more phase shift. It is
in the transformer design details that set the amount
and balance between those effects, and mostly a func-
tion of the core lamination material and size (weight
or bulk), but also a function of the number of turns of
wire, and how the transformer is driven, and the ex-
pected load. We design and manufacture these trans-
formers in house at Manley Labs.
At very high frequencies, the biggest effect is a ultra-
sonic roll-off. This can be as gentle as 6 dB per oc-
tave for several octaves but typically becomes 18 dB
per octave. In fact, the way that capacitance between
windings and leakage inductance interact, usually
creates a signicant bump in the frequency response
somewhere between 30 kHz and 100 kHz, which is
then tamed as standard procedure, by adding a re-
sistor and capacitor at the output or secondary, leav-
ing a smooth predictable roll-off usually around 80k
– 120 kHz. This still leaves some phase shift in the
5k - 20kHz range which is audible and gives one the
impression that the highs are softer and don’t extent
to innity.
This may surprise some people, but some designers
and researchers including yours truly, have experi-
mented and determined for themselves, at least, that
we might need a frequency response out to 500kHz or
1 megaHz to completely avoid any audible phase shift
in analog audio circuits and where absolute transpar-
ency is the goal. Then again, our ears adjust rapidly to
rather drastic roll-offs even as low as 10kHz and we
often choose a rolled-off high frequency response as
being more pleasant and comfortable. And some might
say, “no microphone or speaker can reproduce those
frequencies, so why bother?” but these effects are rela-
tive and additive, so every little bit may be audible
for those that can compare. And considering the best
audio systems only approximate full range live per-
formances, then maybe one of the signicant reasons,
is these infra-sonic and ultra-sonic roll-offs happening
too early, causing phase shift in the audible spectrum
and audible time smear. Dynamic performance is an-
other reason, but lets not dwell on that now. Given the
capabilities of modern audio, and the demands of the
audience, much of the goal is creating illusions and
emotional impact. This is how we should approach the
controls on the TNT, and maybe what should become
the criteria for choosing it against other preamps.
By now, you have probably correctly guessed that
turning the IRON control counter-clockwise results in
a cleaner, tighter bottom and extension in the highs.
Turning the IRON control clockwise results in a
rounder, smoother, warmer and softer tone. The mids
won’t be affected much, and mostly only in a rela-
tive way compared to the lows and highs, but if your
ears are great, you might notice a subtle effect with
IRON maxed, where the mids arrive slightly before
the lows and highs and that this is a big part of the
vintage sound. And if you have been reading carefully,
the transformer is biased in “70’s” mode so the IRON
control will have a slightly different (and greater) ef-
fect. You may have also picked up that the IRON knob
acts like an EQ knob, where it has near zero effect as a
circuit when the knob is straight up at 12:00.
We also mentioned that the ¼” output does not use
the transformer but is affected by the IRON knob. As
before, the IRON circuit is essentially bypassed when
the knob is straight up. Turning it counter-clockwise
introduces the transformer correction circuit, and with
this output, creates an Anti-IRON effect. Extreme
highs and lows are boosted slightly. As the Iron knob
is turned up, you introduce the effects of a transformer
into a transformerless output.
17

The ¼” transformerless output has a switch on the
back panel that allows it to PROPERLY drive +4 dBm
balanced inputs, +4 dBm (pin 2 hot) unbalanced inputs
(rare enough), and –10 dBu unbalanced inputs. In each
case, a very stable very and low output impedance is
given that does not suffer and cause common mode re-
jection problems when driving less than perfect cables
and inputs. Typical cross-coupled line drivers magnify
their source resistors while attempting to deal with im-
balances, which only magnies common mode rejec-
tion problems. For example, a great input stage may
have a CMRR spec of 60 dB at 1kHz, (and not in the
specs is that this typically drops to 30 dB at 20K, may
or may not be 80 dB at 60 Hz, and may be 30 dB at 10
Hz), but CMRR is more dependent on the output im-
pedance match of the device driving it, and that 60 dB
spec can drop to 20 dB when there is a 10% difference
between source resistance from Pin1 & Pin2. Cross-
coupled line drivers create CMRR problems for the
sake of idiot-proong and people using funky cables
and adapters. The TNT just uses a switch.
Transformers have traditionally been great at the idi-
ot-proong aspect and are very “forgiving” and solve
more practical connection issues than they create.
However, the back panel switch does have an effect
on the XLR transformer output. For both ¼” and XLR
outputs, in the “+4 balanced” mode, headroom reach-
es +30 dBm comfortably, but drops to +24 dBm when
the switch is set to “+4 unbalanced”, which probably
close to maximum level of most A to D converters.
This might be used to choose which box clips rst and
best. The impedance on pin2 and pin3 remains equal
and constant and low, so it will work better than most
balanced outputs into a balanced input even though
it is labeled “unbalanced”. In other words, when the
switch is set for
“unbalanced”, it will drive both balanced and unbal-
anced inputs ne, and unbalanced inputs at the right
level (no 6 dB drop), but does have 6dB less head-
room, which should still be good enough in most
situations (balanced into balanced is the best choice
generally). In the “-10 unbalanced” mode the ¼” jack
drops the appropriate 12 dB (not 14) and the XLR
drops 6 dB. Much semi-pro and most consumer gear is
happiest with –10 dBu signals, but you may need a ¼”
to RCA adapter. Again this can be used in some situ-
ations other than “standard procedures”. One can use
one output to drive an input in one room, the other to
a different room (like an amp in the studio or a remote
truck) and avoid a lot of hassle with splitter boxes or
ground loops and interaction.
Please note that the tube (T) channel has a different
output arrangement, uses different technology, has a
¼” output that is only unbalanced and doesn’t have the
back panel switch, yet the ¼” output will still be OK
to drive balanced inputs, especially if one is trying to
avoid transformers today.
18

TROUBLESHOOTING
There are a number of possible symptoms of something not quite right; some may be interfacing, others we will
touch on as well. If you suspect a problem, the following paragraphs should help.
NO POWER, NO INDICATORS, NADA - Probably something to do with AC power. Is it plugged in? Check the
fuseon the back panel. A blown fuse often looks blackened inside or the little wire inside looks broken or it’s resistance
measures higher than 2 ohms. A very blackened fuse is a big hint that a short occured. Try replacing the fuse with a good
one of the same value and size. If it blows too, then prepare to send the unit back to the dealer or factory for repair. The
fuse is a protection device and it should blow if there is a problem. If the unit works with a new fuse, ne, it works.
Sometimes fuses just blow for unknown reasons.
LIGHTS BUT NO SOUND - First try plugging the in and out cables into each other or some other piece of gear to
verify that your wires are OK. If not x them or replace them. Assuming that cables passed sound - it probably is still
a wiring thing. The output XLRs are transformer balanced which require both PIN 2 and PIN 3 to be connected some-
where. When driving an unbalanced input (inserts on some consoles) PIN 3 needs to be grounded or connected to PIN
1. Same with the unbalanced 1/4 inch jacks - if driving a balanced input you can’t ignore the negative side. It needs to
be connected to the sleeve of the phone plug. Another way to do basically the same thing is join PIN 1 and PIN 3 on the
XLR male at the destination. Easiest way - Use the balanced with balanced, unbalanced with unbalanced. That is why the
options are there.
LEVELS SEEM TO BE WRONG, NO BOTTOM - Several possible scenarios. Manley uses the professional standard
of +4 dBm = Zero VU = 1.23 volts AC RMS. A lot of semi-pro gear uses the hi- reference of -10 dBm = Zero VU. This
is a 14 dB difference that will certainly look goofy and may tend to distort. Often there are switches on the semi-pro gear
to choose the pro reference level. If the loss looks close to 6 dB and it sounds thin then one half of the signal is lost. The
cause is probably wiring again. One of the two signal carrying wires (the third is ground / shield on pin 1) is not happen-
ing. Check the cables carefully because occasionally a cable gets modied to work with a certain unit and it seems to
work but its wrong in other situations. If only one side of the TNT exhibits this problem, it may be a problem in the TNT.
HUM - Once again - several possibilities - several cures. Most likely it is a ground loop. Ideally each piece of gear
should have one ground connection and only one. However, the short list of grounds include the AC mains plug, the
chassis bolted to a rack with other gear, each input and each output. The two most common procedures are: try a 3 pin to
2 pin AC adapter (about a dollar at the hardware store).This while legal in many countries can be dangerous. Method two
- cutting the shield on one end of each cable. This is done by some studios at every female XLR to “break” all ground
loops. All the other gear in the rack is “dumping” ground noise onto the ground. Try removing the EQ from the rack so
that it is not touching any metal. You just may have cured a non-loop hum. Some gear radiates a magnetic eld and some
gear (especially if it has audio transformers or inductors) might receive that hum. A little distance was all it took. It is
worth a few placement experiments if you notice hum.
IT MAKES NOISES WHEN THE FRONT PANEL IS TAPPED - An easy one. Some tubes become microphonic
over time. That means they start acting like a bad microphone. Vibration has caused the supports for the little parts in the
tube to loosen and now the tube is sensitive to vibration. Easy - Replace the tube. Which one? The one that makes the
most noise when you tap it. Usually this will be the smaller tube closest to the front. The TNT will have to be on, con-
nected and speakers up but not too loud for the sake of your speakers.
19

Audio Precision 06/26/06 18:06:03
-160
-20
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
d
B
2k 16k4k 6k 8k 10k 12k 14k
Hz
Audio Precision 06/26/06 17:55:11
FFT SPECTRUM of THD Residual @ 1kHz
-160
-20
-150
-140
-130
-120
-110
-100
-90
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-70
-60
-50
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d
B
2k 16k4k 6k 8k 10k 12k 14k
TUBE CHANNEL DISTORTION FFT
TUBE CHANNEL DRIVEN JUST 2 dB HOTTER
The TOP graph shows the distortion harmonics just prior to full clipping.
Notice both even and odd harmonics and a smooth decay of upper harmonics.
The BOTTOM graph shows just slightly hotter signal brings the unit into
deeper clipping and the symmetrical clip brings in more odd harmonics
and involves more upper harmonics.
These graphs illustrate that tube circuits do not just create even harmonics
and that they don’t just create low order harmonics, nor does clipping just produce
odd harmonics. It is a little more complex than that. It depends on the topology,
circuit details, levels and measurement techniques.
What matters in this case is the lack of harmonics before clipping (low THD) which
is not graphed here because it is just a boring noise floor
20