Behringer Tube Ultragain T1953 User manual

TUBE ULTRAGAIN T1953
Version 1.2 December 2002
Users Manual
ENGLISH

2
TUBE ULTRAGAIN T1953
This symbo , wherever it appears, a erts
you to important operating and mainte-
nance instructions in the accompanying
iterature. Read the manua .
SAFETY INSTRUCTIONS
CAUTION: To reduce the risk of e ectric shock, do not remove
the cover (or back). No user serviceab e parts inside;
refer servicing to qua ified personne .
WARNING: To reduce the risk of fire or e ectric shock, do not
expose this app iance to rain or moisture.
DETAILED SAFETY INSTRUCTIONS:
A the safety and operation instructions shou d be read before the app iance is operated.
Retain Instructions:
The safety and operating instructions shou d be retained for future reference.
Heed Warnings:
A warnings on the app iance and in the operating instructions shou d be adhered to.
Follo instructions:
A operation and user instructions shou d be fo owed.
Water and Moisture:
The app iance shou d not be used near water (e.g. near a bathtub, washbow , kitchen sink, aundry tub, in a wet
basement, or near a swimming poo etc.).
Ventilation:
The app iance shou d be situated so that its ocation or position does not interfere with its proper venti ation.
For examp e, the app iance shou d not be situated on a bed, sofa, rug, or simi ar surface that may b ock the
venti ation openings, or p aced in a bui t-in insta ation, such as a bookcase or cabinet that may impede the
f ow of air through the venti ation openings.
Heat:
The app iance shou d be situated away from heat sources such as radiators, heat registers, stoves, or other
app iances (inc uding amp ifiers) that produce heat.
Po er Source:
The app iance shou d be connected to a power supp y on y of the type described in the operating instructions
or as marked on the app iance.
Grounding or Polarization:
Precautions shou d be taken so that the grounding or po arization means of an app iance is not defeated.
Po er-Cord Protection:
Power supp y cords shou d be routed so that they are not ike y to be wa ked on or pinched by items p aced
upon or against them, paying particu ar attention to cords and p ugs, convenience receptac es and the point
where they exit from the app iance.
Cleaning:
The app iance shou d be c eaned on y as recommended by the manufacturer.
Non-use Periods:
The power cord of the app iance shou d be unp ugged from the out et when eft unused for a ong period of time.
Debris and Liquid Entry:
Care shou d be taken that debris and/or iquids do not enter the enc osure through openings.
Damage Requiring Service:
The app iance shou d be serviced by qua ified service personne when:
- The power supp y cord or the p ug has been damaged; or
- Debris or iquid has entered the app iance; or
- The app iance has been exposed to rain; or
- The app iance does not appear to operate norma y or exhibits a marked change in performance; or
- The app iance has been dropped, or the enc osure damaged.
Servicing:
The user shou d not attempt to service the app iance beyond that which is described in the operating instruc-
tions. A other servicing shou d be referred to qua ified service personne .
This symbo , wherever it appears,
a erts you to the presence of
uninsu ated dangerous vo tage inside
the enc osurevo tage that may be
sufficient to constitute a risk of shock.

3
TUBE ULTRAGAIN T1953
FOREWORD
Dear Customer,
We thank you for expressing your confidence in BEHRINGER products by purchasing the BEHRINGER
TUBEULTRAGAIN. It is one of my most p easant tasks to write this preface, as our engineering team has
made it possib e to enhance the traditiona tube circuitry design (particu ar y for our VINTAGER series of
products), and adapt it to meet the high sound qua ity and dynamics requirements of modern, pro- eve audio
techno ogy. The fact that we are sti fascinated by antique tube radios and amps as we as the fine and warm
tona character that we usua y associate with them, are the reasons why vacuum tubes have kept their ground
even in state-of-the-art circuit topo ogies used especia y in professiona audio techno ogy or high-end devices.
We are particu ar y proud that we have found an extreme y effective symbiosis between so id-state and tube
techno ogies making them affordab e to anybody interested in audio techno ogy. As a ways, our top-priority
concern when deve oping this device was the demanding end user, in other words: you. It was our major goa
to meet your demands. Sure, it meant a ot of hard work to deve op such a product, but the fun has made it a
worthwhi e. The shine in the eyes of the many interested musicians at the Music Fair 1997, when they saw our
VINTAGER mode s for the first time, was a asting incentive driving our deve opment efforts.
It is our phi osophy to share our joy with you, because you are the most important member of the BEHRINGER
fami y. With your high y competent suggestions for new products youve great y contributed to shaping our
company and making it successfu . In return, we guarantee you uncompromising qua ity (manufactured under
ISO9000 certified management system) as we as exce ent technica and audio properties at an extreme y
favorab e price. A of this wi enab e you to fu y unfo d your creativity without being hampered by budget
constraints.
We are often asked how we can make it to produce such high-grade devices at such unbe ievab y ow prices.
The answer is quite simp e: its you, our customers! Many satisfied customers means arge sa es vo umes
enab ing us to get better conditions of purchase for components, etc. Isnt it on y fair to pass this benefit back
to you? Because we know that your success is our success, too!
I wou d ike to thank a peop e whose he p on Project TUBEULTRAGAIN has made it a possib e. Everybody
has made very persona contributions, starting from the designers of the unit via the many staff members in our
company to you, the user of BEHRINGER products.
My friends, its been worth the troub e!
Thank you very much,
U i Behringer

4
TUBE ULTRAGAIN T1953
T1953
TUBEULTRAGAIN
Tube Microphone/Line Preamplifier
sU tra ow-noise discrete microphone/ ine preamp ifier with se ected 12AX7 tubes
sULTRA-TUBE circuitry (UTC) adds desired amount of warmth without additiona noise
s Mic input stages are based on high qua ity, discrete conjugate transistor pair circuitry
s U tra-wide bandwidth from 18 Hz to 30 kHz for open sound
sWarmth contro a ows precise dosage of desired tube effect
sComp ete y versati e DI-Box due to servo-ba anced inputs and outputs
sLeve converter from -10 dBV to +4 dBu
sSoft mute +48 V phantom power to avoid switch-on thumps
sFu y tunab e and switchab e 12dB high-pass fi ter
sSwitchab e phase reverse to correct phase prob ems
sU tra ow-noise 4580 audio operationa amp ifiers offer outstanding sound performance
sHigh y accurate metering with true RMS eve detection
sServo-ba anced go d-p ated XLR and 1/4" TRS inputs and outputs
sHigh-qua ity detented potentiometers and switches with vintage-sty e knobs
sHuge back- it ana og VU meters and sty ish retro design
sBEHRINGERs high-performance OT-1 output transformer retrofitab e
sManufactured under ISO9000 certified management system

5
TUBE ULTRAGAIN T1953
TABLE OF CONTENTS
1. INTRODUCTION..................................................................................................................... 6
1.1 The concept .................................................................................................................................... 6
1.2 Before you get started ..................................................................................................................... 7
1.3 Contro e ements ............................................................................................................................. 7
2. OPERATION .......................................................................................................................... 10
3. APPLICATIONS ..................................................................................................................... 11
3.1 The TUBEULTRAGAIN as a microphone preamp ........................................................................... 11
3.2 The TUBEULTRAGAIN as a eve converter ................................................................................... 12
3.3 The TUBEULTRAGAIN as a direct injection box ........................................................................... 12
3.4 The TUBEULTRAGAIN as tube interface ...................................................................................... 12
4. TECHNICAL BACKGROUND .............................................................................................. 12
4.1 Audio dynamics ............................................................................................................................ 13
4.1.1 Noise as a physica phenomenon ....................................................................................... 13
4.1.2 What are audio dynamics? ................................................................................................. 14
4.2 The tubes used in the TUBEULTRAGAIN ..................................................................................... 15
4.3 Tube history .................................................................................................................................. 15
4.4 Design and functiona princip e of tubes ........................................................................................ 16
4.5 Properties of tubes ........................................................................................................................ 17
4.6 The best of both wor ds ................................................................................................................. 18
4.7 UTC circuit .................................................................................................................................... 18
4.8 Studio app ications ........................................................................................................................ 18
4.9 Phantom power ............................................................................................................................. 19
5. INSTALLATION ..................................................................................................................... 20
5.1 Rack mounting .............................................................................................................................. 20
5.2 Mains connection .......................................................................................................................... 20
5.3 Audio connections ........................................................................................................................ 21
5.4 Transformer-ba anced output (option) ............................................................................................ 21
6. SPECIFICATIONS ................................................................................................................. 22
7. WARRANTY ........................................................................................................................... 23

6
TUBE ULTRAGAIN T1953
1. INTRODUCTION
With the TUBEULTRAGAIN you have purchased an extreme y musica and f exib e microphone preamp ifier.
Our ULTRAGAIN range of devices has been a hit ever since we introduced our first mode some 5 years ago.
This high-end microphone preamp is based on many years of experience and findings in amp ifier techno ogy
and is used throughout the wor d in renowned studios, sound reinforcement systems as we as in broadcast
and te evision studios. Improving the egendary ULTRAGAIN even further was a rea cha enge, and we are
proud of our success. The BEHRINGER TUBEULTRAGAIN meets highest and no-compromise requirements
in terms of operation, sound, specifications and workmanship.
Even at the conception of the TUBEULTRAGAIN it was c ear that we had to combine the outstanding technica
specifications of our ULTRAGAIN with a warm tube sound. We are therefore proud to be ab e to present the
TUBE ULTRAGAIN, a device featuring our new y deve oped UTC vacuum tube circuit combined with a
no-compromise approach.
The heart of the TUBEULTRAGAIN is an extreme y ow-noise microphone preamp circuit that uses discrete
components to produce a high y transparent sound. In combination with our BEHRINGER tube techno ogy, the
operationa amp ifiers 4580 and a sophisticated circuit topo ogy, the TUBEULTRAGAIN yie ds exce ent noise
and distortion properties! The switchab e +48 V phantom power supp y a ows for connecting a most any kind
of microphone and suppresses power-up thumps with its soft mute function.
Our engineering team has made it possib e to enhance the traditiona tube circuitry (particu ar y for our
TUBEULTRAGAIN) and adapt it to meet the high sound qua ity and dynamics requirements of modern,
pro- eve audio techno ogy. The fact that we are sti fascinated by antique tube radios and amps as we as
the fine and warm tona character that we usua y associate with them, are the reasons why vacuum tubes
have kept their ground even in state-of-the-art circuit topo ogies used especia y in professiona audio
techno ogy or high-end devices. We are particu ar y proud that we have found a high y effective symbiosis
between so id-state and tube techno ogies making them affordab e to a most anybody in audio techno ogy.
With the exception of 2 12AX7/ECC83 tubes, the TUBEULTRAGAIN T1953 is based on SMD techno ogy
(Surface Mounted Device). These subminiature components known from aerospace app ications ensure both
extreme packing density and greater re iabi ity.
Speaking of re iabi ity: qua ity assurance p ays an ever important ro e in todays production methods. To
guarantee even greater operationa re iabi ity, our products are manufactured under one of the most stringent
industria qua ity assurance systems: ISO9000. This European certification is granted exc usive y to
companies whose manufacturing processes are in fu comp iance with this accurate standard.
1.1 The concept
The phi osophy behind BEHRINGER products guarantees a no-compromise circuit design and emp oys the
best choice of components. The op-amps, type 4580, used in the TUBEULTRAGAIN are chosen for their
superior signa -to-noise ratio, ow distortion and inear performance. Additiona y, the TUBE ULTRAGAIN uses
high qua ity resistors and capacitors with very tight to erances, high-grade switches as we other se ected
components.
The TUBEULTRAGAIN uses 12AX7 / ECC83 tubes. These triodes are capab e of hand ing a arge dynamic
range with itt e microphony. Add to this their re ative ruggedness and above average ife span and you can see
why its one of the most popu ar and re iab e pre-amp tubes on the market. These features a so ensure you
their avai abi ity for many years to come.
Balanced inputs and outputs
As standard, the BEHRINGER TUBE ULTRAGAIN is insta ed with e ectronica y servo-ba anced inputs and
outputs. The new circuit design features automatic hum and noise reduction for ba anced signa s and thus
a ows for troub e-free operation, even at high operating eve s. Externa y induced mains hum etc. wi be
effective y suppressed. The automatic servo-function recognizes the presence of unba anced connectors and
adjusts the nomina eve interna y to avoid eve differences between the input and output signa s
(correction 6dB).
Transformer-balanced outputs (optional)
In contrast to e ectronic ba ancing, the use of transformer-ba anced outputs offers the advantage of ga vanic
separation between units. E ectrica potentia differences and ground oops in audio insta ations do not
1. INTRODUCTION

7
TUBE ULTRAGAIN T1953
therefore impair the performance of the units. The transformer-ba anced outputs, common y used in radio and
TV engineering, can a so be fitted retrospective y upon request. The BEHRINGER transformer OT-1 is
designed to the highest exacting standards and is avai ab e as an accessory.
1.2 Before you get started
Your BEHRINGER TUBEULTRAGAIN was carefu y packed in the factory and the packaging was designed to
protect the unit from rough hand ing. Neverthe ess, we recommend that you carefu y examine the packaging
and its contents for any signs of physica damage, which may have occurred in transit.
+If the unit is damaged, please do not return it to us, but notify your dealer and the shipping
company immediately, other ise claims for damage or replacement may not be granted.
Shipping claims must be made by the consignee.
The BEHRINGER TUBEULTRAGAIN fits into two standard 19" rack units of space (3 1/2" / 89.5 mm). P ease
a ow at east an additiona 4" depth for the connectors on the back pane .
+Be sure that there is enough space around the unit for cooling and please do not place the
TUBEULTRAGAIN on high temperature devices such as po er amplifiers etc. to avoid
overheating.
The mains connection of the TUBEULTRAGAIN is made by using the supp ied cab e. It meets a of the
internationa safety certification requirements. P ease make sure that a units have a proper ground
connection.
+Before you connect your TUBEULTRAGAIN to the mains, please make sure that your local
voltage matches the voltage required by the unit!
As a standard the audio inputs and outputs on the BEHRINGER TUBEULTRAGAIN are fu y ba anced. If
possib e, connect the unit to other devices in a ba anced configuration to a ow for maximum interference
immunity. The automatic servo function detects unba anced connections and compensates the eve difference
automatica y (6dB correction).
1.3 Control elements
Fig. 1.1: Front panel of the TUBEULTRAGAIN
The front pane of the BEHRINGERTUBEULTRAGAIN consists of two identica channe s with four switches,
four rotary contro s and 4 ana og meters.
1. INTRODUCTION

8
TUBE ULTRAGAIN T1953
Fig. 1.2: Control element on the front panel
1Use the MIC/LINE switch to togg e between MIC and LINE modes. When the switch in up position, the
unit works in MIC mode (now you can activate the +48 V switch if required; in LINE mode this function
is disab ed). The new y deve oped UTC circuitry is active in both modes.
+Please note that the input phone jack is disabled in MIC mode, i.e. you must use the XLR
connector to access the microphone amp.
2This +48 V switch activates the +48 V phantom power circuit that uses the signa eads to supp y
condenser microphones with the required operating vo tage.
+Please check the connected signal source for matching specifications before you s itch
phantom po er on, so as to avoid damage to the microphone, etc.
3The CLIP LED signa s that a eve of at east +18dBu is present after the microphone amp stage. With
too high a eve the CLIP LED warns you to reduce the gain with the MIC TRIM contro , so as to avoid
distortion caused by over oading. During norma operation, the LED shou d not ight up at a .
4The MIC TRIM contro is enab ed in MIC mode on y and a ows for app ying gain from 10 to 60dB to the
input signa . In view of the extreme y high gain eve s that can be app ied, you shou d verify that the gain
contro is proper y set before you power up the unit. In case of doubt, set the contro fu y counter-
c ockwise, and start from there s ow y raising the gain. High gain settings and the resu ting eve s can
damage subsequent devices.
5With the PHASE REVERSE switch the input signa is reversed in phase by 180°. This function is
avai ab e both in MIC and LINE modes.
6When the high pass fi ter is in high position, the FREQUENCY contro defines the fi ters cut-off
frequency. With a setting range from 12 to 350Hz the fi ters main task is to e iminate bottom-end
rumb e noise, etc.
7The HIGH PASS switch activates/deactivates the fi ter.
1. INTRODUCTION

9
TUBE ULTRAGAIN T1953
Fig. 1.3: Tube ection of the TUBEULTRAGAIN
8Use the LEVEL contro to set the signa gain at the input of the tube stage. The gain can be set from
-20 to +20dB, i.e. the signa can be attenuated or amp ified by 20dB. When the contro is at its center
position, the eve is una tered. This contro is active in both MICROPHONE as we as LINE mode. Use
this contro to adapt the TUBE ULTRAGAIN to either home-recording eve (-10dBV) or professiona
eve (+4dBu). When this eve is too ow the tube effect becomes ess audib e and the signa -to-noise
ratio deteriorates.
9The PEAK LED above the LEVEL contro warns you of over oad of the unit. The LED shou d not ight up
during norma use. If the LED ights up frequent y, reduce the eve with the LEVEL contro to avoid distortion.
10 The VU meter disp ays the output eve if the TUBE ULTRAGAIN in a range from -20to +2dB. The 0dB
marker corresponds to the studio reference eve of +4dBu. Set the LEVEL contro so that the eve
meter just touches the red zone. A ways try to optimize the signa -to-noise ratio using this meter.
11 With the WARMTH contro you can set the amount of harmonics that are added to the origina signa .
This contro s the tube sound.
12 The WARMTH meter disp ays the amount of added harmonics. With this meter you can easi y reach an
optimum setting for the WARMTH contro .
13 With the POWER switch the TUBEULTRAGAIN is turned off and on. You shou d a ways make sure
that the POWER switch is in the Off position when initia y connecting the unit to the mains.
+Please note that the POWER s itch does not completely disconnect the device from the mains.
If the device is not in use for a long period of time, please disconnect it from the mains by
unplugging the po er cord from the po er socket.
15 17
1614
Fig 1.4: Back panel of the TUBE ULTRAGAIN
1. INTRODUCTION

10
TUBE ULTRAGAIN T1953
14 SERIAL NUMBER. P ease comp ete and return the warranty card within 14 days of the date of
purchase. Otherwise, you wi ose your right to the extended warranty. A ternative y, you can register
on ine at our website under www.behringer.com.
15 FUSE HOLDER / VOLTAGE SELECTION. Before connecting the T1953, confirm that the vo tage
disp ay matches your oca mains vo tage. When rep acing the fuse, you must a ways use the same
type. In many units the fuse ho der can be insta ed in one of two positions, a owing you to switch
between 230 V and 120 V. If you wish to operate a unit outside Europe at 120 V, then a stronger fuse
must be used (see chapter 6 SPECIFICATIONS). The mains connection is made via the IEC
receptac e. An appropriate mains cab e is inc uded.
16 AUDIO IN. These are the audio inputs of your TUBE ULTRAGAIN, avai ab e both as ba anced 1/4" TRS
and XLR connectors. The XLR connector is the common mic/ ine input. Both the XLR and the jack
connector accept unba anced as we as ba anced signa s. See chapter 5 INSTALLATION when wiring
unba anced.
17 AUDIO OUT. These are the audio outputs of your TUBEULTRAGAIN. Matching 1/4" TRS and XLR
connectors are wired in para e . The nomina eve is +4dBu. The maximum output eve is +16dBu.
2. OPERATION
Before you can use the BEHRINGER TUBEULTRAGAIN as a preamp, we recommend that you study the
various functions of the device. The high gain factors provided by the microphone preamp can produce extreme
eve s on the output side, which may damage subsequent devices. So, you shou d start with the fo owing basic
setting:
&RQWROHOHPHQW 6HWWLQ
J
+48 V switch OFF
MIC TRIM control 10 dB
MICROPHONE/LINE switch LINE
PHASE REVERSE switch OFF
HIGH PASS switch OFF
LEVEL control 0 dB
Tab. 2.1: Ba ic etup of the TUBEULTRAGAIN
Reduce the vo ume eve of the subsequent audio system to a minimum, and connect a microphone to the XLR
input connector on the BEHRINGER TUBEULTRAGAIN. Use either the 1/4" TRS or XLR output connectors to
connect the audio system. Owing to its output-side servo-ba ancing circuit, the TUBEULTRAGAIN detects
whether you use a ba anced or unba anced configuration and adjusts the eve interna y.
Now, power up the entire equipment and press the MIC/LINE switch upwards to activate the microphone
preamp. If you wish to use a condenser mic requiring +48 V phantom power, p ease press the +48 V switch.
+Please make sure that you are using an appropriate microphone before you s itch on the
+48 V supply. Read the operating instructions accompanying the microphone. Some condenser
mics might need another type of po er supply, older dynamic microphones could be
damaged by the +48 V voltage, and unbalanced microphones should never be operated in
combination ith a +48 V po er supply.
Configure the equipment according to the app ication on hand, speak into the microphone and turn the GAIN
contro c ockwise unti the 0dB LED ights up. If your DAT recorder, mixing conso e or other subsequent
devices have high-precision eve meters, you can use these to verify the correct eve setting.
The maximum output eve depends on the device that fo ows next in the audio chain, and must therefore be
set specifica y. The high-precision eve meter on the TUBEULTRAGAIN indicates the current operating eve .
The CLIP LED ights up at a eve of +18dBu signa ing that you have an additiona headroom of 5dB avai ab e,
before the microphone preamp starts over oading. If distortion/over oading occurs at high vo ume eve s, you
shou d reduce the gain with the MIC TRIM contro .
2. OPERATION

11
TUBE ULTRAGAIN T1953
The LEVEL control
The LEVEL contro sets the signa gain at the input of the tube stage. Use this contro to adapt the
TUBE ULTRAGAIN to either home recording eve (-10dBV) or professiona eve (+4dBu). When this eve is
too ow the tube effect becomes ess audib e and the signa -to-noise ratio deteriorates.
To obtain the best possib e signa -to-noise ratio and subsequent y the best possib e sound, keep an eye on the
VU eve meter. If the eve at the input of the tube stage is to ow you wi ose the tube sound and have a higher
noise f oor. Use the CLIP LED above the meter to ensure that the eve is not set too high. This LED may ight
up brief y at signa peaks but shou d never ight up constant y.
When using the TUBEULTRAGAIN as microphone amp ifier, set the LEVEL contro to 0dB for optimum
signa -to-noise ratio. Adjust the sensitivity with the MICTRIM contro s. If so desired you can even overdrive the
tube stages de iberate y to gain a specia effect. When the tubes are overdriven severe y the effect resemb es
the overdriving of a guitar amp. This is comp ete y different from the subt e effect of the WARMTH contro . Use
the contro s with discretion, remember: ess is more.
The PHASE REVERSE s itch
The PHASE REVERSE switch reverses the audio signa s phase by 180°. Usua y, you wont need this switch.
However, in some cases, it might be necessary to reverse the signa phase, for examp e, if a microphone cab e
has been connected incorrect y (pins 2 and 3 interchanged), or if severa microphones are used and specific
circumstances with regard to room acoustics are causing prob ems (e.g. frequency cance ations are usua y
caused by phase prob ems). The phase reverse function wi he p you ocate and e iminate any such prob em.
The HIGH PASS s itch
When you pick up acoustic signa s with microphones, it is usua y necessary to e iminate ow-end signa
portions, such as rumb e or pop noise, or other interference frequencies. Often, such frequencies have very
high amp itudes and do not on y deteriorate the sound qua ity but can a so damage the power amps or
speakers. Your TUBEULTRAGAIN features a tunab e high pass fi ter with a very high s ope. Activate the HIGH
PASS switch and adjust the FREQUENCY contro , so that any disturbing frequencies are faded out as much
as possib e, with the east damage done to the actua audio signa s. Press/togg e the switch severa times to
make an A/B comparison.
The WARMTH control
The UTC circuitry forms an integra part of the BEHRINGERTUBEULTRAGAIN. It provides the distinct tube
sound. Gent y turn the contro c ockwise to add increasing amounts of harmonics. It improves the
transparency of other instruments, particu ar y those rich in upper harmonics. The WARMTH meters provide an
instant overview of the process.
3. APPLICATIONS
This section describes some typica app ications of the BEHRINGER TUBEULTRAGAIN. Starting from the
fo owing basic settings you can use it to so ve the majority of audio prob ems.
P ease take your time to study the app ication examp es, so as to be ab e to fu y exp oit the TUBEULTRAGAIN
and its variety of features.
Basica y, the TUBEULTRAGAIN can be used in five areas of app ication:
1. Using the TUBEULTRAGAIN as a high-qua ity microphone preamp.
2. Using the TUBEULTRAGAIN to convert home recording to studio eve s, and vice versa.
3. Using the TUBEULTRAGAIN to ba ance unba anced signa s (DI-box).
4. Using the TUBEULTRAGAIN to enhance the sound of the program materia by adding tube warmth.
3.1 The TUBEULTRA AIN as a microphone preamp
Hook up a microphone and set the basics setting as described in chapter 2. Turn the WARMTH contro fu y
counterc ockwise and you have a very pure and neutra mic preamp with exce ent noise and distortion figures.
Turn the WARMTH contro c ockwise to increase the tube sound with the UTC tube stage.
3. APPLICATIONS

12
TUBE ULTRAGAIN T1953
3.2 The TUBEULTRA AIN as a level converter
Semi-professiona devices in hi-fi and home recording environments are usua y operated with a nomina eve of
-10dBV (0.316 V), whi e the eve used in studios is 0dBu (0.775 V) or +4dBu (1.23 V). So, when you connect
devices of both types to each other, you shou d do this via some kind of eve trans ator.
The BEHRINGER TUBEULTRAGAIN is exce ent y suited for this app ication. In LINE mode, the LEVEL
contro a ows you to raise or ower the input signa eve by as much as 20dB. The functions PHASE
REVERSE and HIGH PASS are a so enab ed in this mode.
3.3 The TUBEULTRA AIN as a direct injection box
When e ectrica signa s de ivered by instruments such as guitars, keyboards, etc. are transported over ong
unba anced ines, the transmission qua ity may be affected by hum or other interference signa s induced in the
cab e. This prob em is usua y encountered in studio or stage environments, where ong cab e engths and
magnetic fie ds of great magnitude may produce interference.
So-ca ed direct injection (DI)-boxes are used to counter this effect: the DI-box converts the unba anced signa
coming from the instrument into a ba anced signa that is sent over the ine. Interference induced in ba anced
cab es is then e iminated by a subsequent ba anced input stage.
Using the TUBEULTRAGAIN for this kind of app ication is easy. Simp y connect the ine output of your
keyboard to the 1/4" TRS input on the TUBEULTRAGAIN. Then use the TUBEULTRAGAINs ba anced output
to send the signa to a stage box or other transmission chain. You can use both the XLR and jack connectors
of the TUBEULTRAGAIN. Set the unit to LINE mode, with any additiona functions switched off (an exception
being the LEVEL contro which can be used to adjust eve s, if necessary).
3.4 The TUBEULTRA AIN as tube interface
In your dai y studio work, the TUBEULTRAGAIN can be used for a variety of app ications that provide subt e
sound enhancement. For examp e, it gives percussion instruments more punch, or improves the
transparency of other instruments, particu ar y those rich in upper harmonics. The source materia is enriched
in sound vo ume and bri iance. Enhanced depth makes it easier to ocate individua instruments. Voca
sounds gain in presence and vo ume, without masking other instruments. Thus, voices become a more integra
part of the overa mix. Synthetic sounds, especia y MIDI guitar sounds become more rea and natura than
without the TUBEULTRAGAIN. So, with the TUBEULTRAGAIN you can adopt a more active approach during
the mixdown process and work out subt eties, whi e focusing particu ar y on the musica aspects of your
recordings.
When the TUBEULTRAGAIN is used as a microphone preamp or as ine driver, this effect can be obtained at
the recording stage. But tracks that are a ready aid can benefit from processing by the TUBEULTRAGAIN.
Make sure that the unit is switched to ine, and that the PHASEREVERSE and HIGHPASS switches are not
engaged. You can insert the TUBEULTRAGAIN in the channe or subgroup inserts of your conso e. The
TUBEULTRAGAIN can a so easi y be used on the entire mix, when inserted in the main mix bus or as a seria
devices between the desk and for instance a DAT recorder the who e mix can benefit from the warm tube
sound.
4. TECHNICAL BACKGROUND
The steady deve opment of modern sound reinforcement systems has made it possib e to produce a most any
eve of oudness. Yet, the increase in oudness goes in ine with a need for optimized audio qua ity. Today,
audiences expect to hear a powerfu and transparent sound. To fu y understand how the BEHRINGER
TUBE ULTRAGAIN works you wi need to know the meaning of a decibe and how audio dynamics work.
With the TUBE ULTRAGAIN, as with any other type dynamics processor the amount of boost/attenuation
app ied is expressed in decibe s (dB). Whats a decibe ? The abbreviationdB is not a unit (a though often used
as one), but describes a ogarithmic proportion. The entire dynamic range of human hearing (from the thresho d
of audibi ity to a jet-airp ane, see fig. 4.1) starts with about 0.00002 Pa (thresho d of audibi ity) and goes up to
130 Pa (thresho d of pain). This a so means that 0dB is not si ence, minus infinitydB wi mean abso ute
si ence.
4. TECHNICAL BACKGROUND

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TUBE ULTRAGAIN T1953
0
20
40
60
80
100
120
140
160
Threshold Of Audibility
Falling Leaves
Recording Studio
Quiet Apartment
Normal Conversation
"Loud" Office
Power Drill
Threshold Of Pain
Jet Engine
Machinery Hall
Sound-Pressure Level (dB SPL)
Fig. 4.1: Dynamic range of human hearing
The range of sound pressure eve s or the dynamic range of human hearing encompasses a factor of 10,000,000.
This enormous range of va ues is difficu t to hand e and additiona y does not represent the subjective
perception of sound, since human hearing tends to use a ogarithmic curve. When an increase in oudness by
the factor two is perceived as one step, four times the oudness eve equa s two steps. So, the decibe is a unit
of measurement that describes a eve in re ation to a reference quantity. To make c ear which reference
quantity is meant, the abbreviation SPL (sound pressure eve ) is sometimes used together withdB. Starting
with a va ue of 0dB SPL (= 2*10-5 Pa) for the thresho d of audibi ity, anydB va ues can be ca cu ated by means
of the fo owing formu a:
/
S
S
=⋅
20 2
1
log
L = e.g. the abso ute sound pressure eve indB SPL
p1 = e.g. a reference sound pressure of 0.00002 Pa
p2 = the sound pressure (in Pa) produced by the sound source to be ca cu ated
og = decima ogarithm.
As can be seen, human hearing has a very wide dynamic range of about 130dB, which surpasses the range
of a DAT or CD p ayer with an approximate range of 96dB. From a physica point of view, a 3dB boost
corresponds to an increase in power by the factor 2. However, the human ear perceives a signa to be twice as
oud as before on y if it is boosted by about 10dB.
4.1 Audio dynamics
As demonstrated, it is possib e to manufacture ana og audio equipment with a dynamic range of up to 130dB.
In contrast to ana og techniques, the dynamic range of digita equipment is approximate y 25dB ess. With
conventiona record and tape recorder techno ogy, as we as broadcasting, this va ue is further reduced.
Genera y, dynamic restrictions are due to noisy storage in transmission media and a so the maximum
headroom of these systems.
4.1.1 Noise as a physical phenomenon
A e ectrica components produce a certain eve of inherent noise. Current f owing through a conductor eads
to uncontro ed random e ectron movements. For statistica reasons, this produces frequencies within the
who e audio spectrum. If these currents are high y amp ified, the resu t wi be perceived as noise. Since a
frequencies are equa y affected, we term this white noise. It is fair y obvious that e ectronics cannot function
4. TECHNICAL BACKGROUND

14
TUBE ULTRAGAIN T1953
without components. Even if specia ow-noise components are used, a certain degree of basic noise cannot
be avoided.
This effect is simi ar when rep aying a tape. The non-directiona magnetic partic es passing the rep ay head can
a so cause uncontro ed currents and vo tages. The resu ting sound of the various frequencies is heard as
noise. Even the best possib e tape biasing can on y provide signa -to-noise ratios of about 70dB, which is not
acceptab e today since the demands of isteners have increased. Due to the aws of physics, improving the
design of the magnetic carrier is impossib e using conventiona means.
4.1.2 What are audio dynamics?
The human ear can detect the most wide ranging amp itude changesfrom the s ightest whisper to the
deafening roar of a jet-p ane. If one tried to record or reproduce this wide spectrum of sound with the he p of
amp ifiers, cassette recorders, records or even digita recorders (CD, DAT etc.), one wou d immediate y be
restricted by the physica imitations of e ectronic and acoustic sound reproduction techno ogy.
The usab e dynamic range of e ectroacoustic equipment is imited as much at the ow end as at the high end.
The therma noise of the e ectrons in the components resu ts in an audib e basic noise f oor and thus
represents the bottom imit of the transmission range. The upper imit is determined by the eve s of the interna
operating vo tages; if they are exceeded, audib e signa distortion is the resu t. A though in theory, the usab e
dynamic range sits between these two imits, it is considerab y sma er in practice, since a certain reserve
must be maintained to avoid distortion of the audio signa if sudden eve peaks occur. Technica y speaking,
we refer to this reserve as headroomusua y this is about 10 - 20dB. A reduction of the operating eve
wou d a ow for greater headroom, i.e. the risk of signa distortion due to eve peaks wou d be reduced.
However, at the same time, the basic noise f oor of the program materia wou d be increased considerab y.
Ear
Microphone Amplifier
Power Amplifier
Tape Recorder
Radio
Cassette
Recorder
P/dB
140
120
100
80
60
40
Fig. 4.2: The dynamic range capabilitie of variou device
It is therefore usefu to keep the operating eve as high as possib e without risking signa distortion in order to
achieve optimum transmission qua ity.
It is possib e to further improve the transmission qua ity by constant y monitoring the program materia with the
aid of a vo ume fader, which manua y eve s the materia . During ow passages the gain is increased, during
oud passages the gain is reduced. Of course it is fair y obvious that this kind of manua contro is rather
restrictive; it is difficu t to detect signa peaks and it is a most impossib e to eve them out. Manua contro is
simp y not fast enough to be satisfactory.
4. TECHNICAL BACKGROUND

15
TUBE ULTRAGAIN T1953
Fig. 4.3: The interactive relation hip between operating level and headroom
The need therefore arises for a fast acting automatic gain contro system which wi constant y monitor the
signa s and which wi a ways adjust the gain to maximize the signa -to-noise ratio without incurring signa
distortion. This device is ca ed a compressor or imiter.
4.2 The tubes used in the TUBEULTRA AIN
A c oser ook at deve opments and trends in audio techno ogy shows that tubes are current y enjoying a
renaissance, in a time when even amateur musicians are free to use digita effects processors and recording
media, and ever more affordab e digita mixing conso es are becoming a natura part of the equipment of many
semi-professiona studios. The manufacturers try with ever new a gorithms to get the most out of DSPs (Digita
Signa Processors), the heart of any digita system.
Sti , many audio engineers, particu ar y o d hands often prefer using both o d and new tube-equipped devices.
As they want to use their warm sound character for their productions, they are ready to accept that these
goodies produce a higher noise f oor than modern, transistor-based devices. As a consequence, you can find
a variety of tube-based microphones, equa izers, preamps and compressors in todays recording and
mastering environments. The combination of semiconductor and tube techno ogies gives you the additiona
possibi ity of using the best of both wor ds, whi e being ab e to make up for their specific drawbacks.
4.3 Tube history
Due to many patent itigations, it is difficu t to determine exact y when the tube was born. First deve opments
in tube techno ogy were reported between 1904 and 1906. It was a research task of that time to find a suitab e
method for receiving and rectifying high frequencies. On Apri 12, 1905, a certain Mr. F eming was granted a
patent for his hot-cathode va ve which was based on Edisons incandescent amp. This va ve was used as a
rectifier for high-frequency signa s. Robert van Lieben was the first to discover (probab y by chance) that the
anode current can be contro ed by means of a perforated meta p ate (grid), one of the mi estones in the
deve opment of amp ification tubes. In 1912, Robert van Lieben fina y deve oped the first tube for the
amp ification of ow-frequency signa s. Initia y, the biggest prob em was to produce sufficient vo ume eve s,
which is why resonance step-ups (though impairing the frequency response) were used to maximize the
attainab e vo ume. Later, the objective was to optimize the e ectroacoustic transducers of amp ifiers in such a
way that a broad frequency band cou d be transmitted with the east distortion possib e. However, a tube-
specific prob em is its non- inear amp ification curve, i.e. it modifies the sound character of the source materia .
Despite a efforts to ensure a arge y inear frequency response, it had to be accepted that tube devices
produce a bad sound. Additiona y, the noise f oor generated by the tubes imited the usab e dynamics of
connected storage media (magnetic tape machines). Thus, a one-to-one reproduction of the audio signa s
dynamics (expressed as the difference between the highest and owest oudness eve s of the program
materia ) proved impossib e. To top it a , tube devices required the use of high-qua ity and often cost y
transducers and sophisticated vo tage supp ies.
4. TECHNICAL BACKGROUND

16
TUBE ULTRAGAIN T1953
With the introduction of semiconductor techno ogies in the fie d of audio amp ification it soon became c ear that
the tube wou d have to give way to the transistor, as this device featured an enormous y enhanced signa -
to-noise ratio, ess comp ex power supp y and improved frequency response. P us, semiconductor-based
circuits can be rea ized much more easi yfor ess money. Two decades ater, the introduction of binary
signa processing meant the beginning of a new era of recording media that provided p enty of dynamic
response and a owed for oss-free copying of audio signa s. As digita media were enhanced, however, many
peop e began to miss the warmth, power and ive iness they knew from ana og recordings. This is why purists
sti today consider digita recordings as steri e in sound.
4.4 Design and functional principle of tubes
Tubes can be rough y c assified according to the number of e ectrodes they use. There are tubes with two,
three or five e ectrodes usua y referred to as diodes, triodes or pentodes.
Fig. 4.4: Diode
The diode contains two e ectrodes in a vacuum g ass bu b that have e ectrica connection to the outside. The
vacuum a ows for a free movement of e ectrons. When one of the e ectrodes is heated up (= thus becoming a
cathode), it begins to emit e ectrons. When a positive dc vo tage is app ied to the other e ectrode (= anode), the
negative e ectrons start to wander from the cathode to the anode. With reverse po arity between cathode and
anode, a current f ow is not possib e because the unheated anode emits more or ess no e ectrons. This design
was used, for examp e, as a rectifier in the power supp ies of amp ifiers. The magnitude and ve ocity of the f ow
of e ectrons depend on the cathodes temperature, the materia it consists of, and the magnitude of the anode
vo tage. When the e ectrons hit the anode they produce heat that is dissipated by using arge anode p ates.
Fig. 4.5: Triode
The triode has an additiona meta grid between anode and cathode. By app ying a negative vo tage, this grid
can be used to contro the interna resistance of the tube, and hence the anode current. When the grid bias
vo tage (vo tage between cathode and grid) becomes negative, the current f owing to the anode is reduced
because the negative y charged grid repe s the arriving e ectrons. As a consequence, there are ess e ectrons
to reach the anode. When the bias vo tage is raised towards zero, the f ow of e ectrons acce erates. When it
fina y becomes zero or even positive, the grid current begins to f ow which considerab y reduces the current
f owing to the anode and can possib y destroy the tube. Triodes are most common y used in preamps, often in
pairs arranged in one tube (twin triode).
4. TECHNICAL BACKGROUND

17
TUBE ULTRAGAIN T1953
Fig. 4.6: Pentode
In a triode the capacitance between grid and anode is a prob em with regard to high frequencies and arge
amp ification factors. For this reason, the pentode has a positive y charged screen grid between the contro grid
and the anode. However, the positive charge of the screen grid attracts e ectrons emitted from the anode p ate
when it is hit by arriving e ectrons. To prevent this e ectron emission, a dece erating or suppressor grid is
p aced between anode and screen grid. As it is negative y charged it b ocks the e ectrons, so that they cannot
reach the screen grid. Pentodes are most common y used in power stages.
4.5 Properties of tubes
In genera , the saturation (overdriving) of both transistor and tube-based circuits resu ts in various types of
distortion. These phenomena are quite comp ex in the rea wor d, but for the sake of a straightforward
mathematica description we are going to c assify them as inear and non- inear distortion. Linear distortion is
produced by frequency-dependent amp ification or attenuation processes such as occurs in a kinds of fi ters
and equa izers. Linear-distortion signa s have the same frequency portions both on the input and output sides,
but with different phase positions and amp itudes. Non- inear distortions have additiona harmonics and
distortion components that were not contained in the origina input signa .
For examp e, when the p ainest of a osci ations, a sine wave with a fixed frequency f, is overdriven, new
osci ations with frequencies of 2*f, 3*f, etc. (integra mu tip es of the origina frequency) are produced. These
new frequencies are referred to as upper harmonics grouped as odd and even harmonics. Un ike the transistor,
saturated tubes most y produce even harmonics which are perceived by the human ear as more p easant in
sound than odd harmonics. Another important aspect ies in the fact that tubes produce distortion more
gradua y than transistors, which is why we speak of the saturation of a tube stage. When you overdrive a
transistor you get a sudden square deformation of the sine signa app ied at the input, which produces an
extreme harmonic spectrum at the output.
Non- inear distortions are measured with a distortion factor that consists of the tota harmonic distortion [k] and
partia harmonic distortions [kn]. The atter are defined as the ratio between the vo tage of a sing e harmonic
and the vo tage of the distorted overa signa . Thus, the content of even harmonics is expressed as k2, k4, ...
and that of odd harmonics as k1, k3, ...
N8
8
QQ
JHV
=
Formula for calculating partial harmonic di tortion
The tota harmonic distortion is the root of a squared distortion factors of the second and third degrees. Since
the higher harmonics have on y itt e impact on the measured resu ts, they can be neg ected.
NNN=+
2
2
3
2
Formula for calculating total harmonic di tortion
In tube circuits the distortion factor k2 is used to describe an effect which the human ear c assifies as
p easant. A so the frequency bands in which distortion occurs p ay an important ro e because the human ear
differentiates very c ear y in the frequency range of human speech.
4. TECHNICAL BACKGROUND

18
TUBE ULTRAGAIN T1953
4.6 The best of both worlds
Despite many efforts neither manufacturers nor deve opers have succeeded so far in simu ating these positive
properties of the tube by means of other devices. Additiona y, the natura capabi ities of the tube to act as a
soft imiter can on y be mimicked with high y sophisticated circuitry. Todays studio techno ogy requirements
are therefore met by a combination of both high-grade semiconductor and tube techno ogies. In this context,
tubes no onger serve their origina purpose as amp ifiers, but are used for the detai ed shaping of sound.
4.7 UTC circuit
In
Out
WARMTH
Fig. 4.7: UTC circuit
The TUBEULTRAGAIN sp its up the audio signa app ied at the input and processes it different y for both
signa paths. Each of the two tube ha ves amp ifies the origina signa and the signa modified in its phase
spectrum (twin triode). Additiona harmonics are produced by s ight y overdriving the tube stage. When the two
signa s are processed by the UTC circuit, the interference noise found in conventiona tube circuits can be
arge y e iminated, and the actua tube effect be added gradua y. The more you turn the Warmth contro to the
right, the more tube sound wi be added to the origina signa .
4.8 Studio applications
In a recording studio tubes do not perform the same task as they do in an overdriven guitar amp, where the
considerab y higher saturation of the tube(s) eads to a fu and often de iberate modification of the input signa
(in many cases combined with a heavy increase in noise f oor eve s). In the studio more subt e effects are
needed. Here, tube circuits add ife to the signa s tona character and increase its power to make itse f heard.
Often, tubes a so increase the signa s perceived oudness (in re ation to the unprocessed signa ), i.e. the
perceived oudness goes up a though the vo ume eve remains the same. This is because the dynamic range
of the app ied audio signa is imited by the tube circuit, whi e the amp itude of the signa with the owest
oudness is raised. Thus, increasing tube saturation produces a s ight compression effect over the entire
dynamic range.
A simi ar effect can be perceived when ana og tape is saturated. This saturation effect a so compresses the
recorded audio materia and produces additiona harmonics.
4. TECHNICAL BACKGROUND

19
TUBE ULTRAGAIN T1953
Video Tape
Compact Disc
Analog Records
FM Radio
Digital Tape (16 Bit)
Analog Tape
dB
100
75
50
25
Analog Mixing Console
Fig. 4.8: Dynamic range of variou media
4.9 Phantom power
Condenser microphones need a specific supp y vo tage po arizing the condenser diaphragm. This vo tage can
be furnished from an interna battery, or an externa power supp y that is either connected direct y to the
microphone or supp ies the vo tage through the microphone cab e. In practice, this technique is usua y referred
to as +48 V or phantom power supp y, and uses the microphone cab e to carry both the audio signa and the
supp y vo tage required for the microphone.
P ease read this chapter thorough y: phantom power can damage the microphone, if used improper y.
Fig. 4.9: Functional diagram of phantom power upply
We speak of phantom power when a microphone cab e is used to carry severa signa s, with a DC vo tage
 ayered on the actua audio signa . The typica phantom DC vo tage is +48 V, which is app ied both to the
positive (pin 2) and negative inputs (pin 3) of the XLR connector, using current- imiting resistors. As the
phantom vo tage is sp it up in a ba anced configuration among the signa eads, there is no need to app y it
direct y to the microphone transducer or the microphone itse f, where it cou d damage the transducer and/or
capsu e. In an unba anced configuration, DC vo tage wou d be app ied direct y, which wou d inevitab y ead to
disturbing noise or cou d even damage the e ectronics.
4. TECHNICAL BACKGROUND

20
TUBE ULTRAGAIN T1953
To e iminate this risk, the BEHRINGER TUBEULTRAGAIN automatica y disab es the unba anced jack in MIC
mode. Microphones can thus on y be connected to the XLR connector.
Never switch on the +48 V supp y when you use unba anced microphones, as this cou d cause e ectrica
damage.
Some peop e ho d that the sound of dynamic microphones is affected when the +48 V supp y is on, or that
ribbon microphones cannot be operated from an input equipped with +48 V phantom power. None of these
statements is true. As a matter of fact, prob ems of this kind are caused by one of the fo owing reasons:
1. When the output transformer of the microphone suffers from a short circuit or eakage current at any point,
disturbing noise, c icks or hum can occur. In this case, you shou d have the microphone repaired.
2. When you connect a microphone whi e the +48 V supp y is switched on, it cannot be guaranteed that both
signa eads of the XLR connectors estab ish the e ectrica contact precise y at the same point of time.
Therefore, detrimenta current cou d f ow because the connection is temporari y unba anced. We recommend
that you switch off the +48 V supp y before you attempt to connect a microphone.
+Please make sure that you are using an appropriate microphone before you s itch on the
+48 V supply. Read the operating instructions accompanying the microphone. Some condenser
mics might need another type of po er supply, older dynamic microphones could be
damaged by the +48 V voltage, and unbalanced microphones should never be operated in
combination ith a +48 V po er supply.
5. INSTALLATION
5.1 Rack mounting
The BEHRINGER TUBEULTRAGAIN fits into two standard 19" rack units of space (3 1/2" / 89.5 mm). P ease
a ow at east an additiona 4" / 10 cm depth for the connectors on the back pane . Be sure that there is enough
air space around the unit for coo ing and p ease do not p ace the TUBEULTRAGAIN on high temperature
devices such as power amp ifiers etc. to avoid overheating.
5.2 Mains connection
The mains connection of the TUBEULTRAGAIN is made by using a mains cab e and a standard IEC
receptac e. It meets a of the internationa safety certification requirements.
+Please make sure that all units have a proper ground connection. For your o n safety, it is
advisable not to remove the ground connection ithin the units or at the supply, or fail to
make this connection at all.
Before you switch on the unit, check that it is configured to match your AC mains vo tage requirements. If it
does not comp y, then it is necessary to switch the operating vo tage to the correct supp y requirements
BEFORE turning on the unit, otherwise the unit cou d be severe y damaged. You wi find this combined fuse
ho der/vo tage se ector at the back, adjacent to the IEC receptac e. IMPORTANT: This does not apply for
general export models hich are built for one operating voltage only.
The AC vo tage se ection is defined by the position of the fuse ho der. If you intend to change the operating
vo tage, remove the fuse ho der and twist it by 180 degrees before you reinsert it. Matching the two markers
monitors the se ected vo tage.
+If the unit is s itched to another operating voltage, the fuse rating must be changed. See the
technical specifications in the appendix.
A safety fuse protects the unit from serious defects. If the fuse b ows, this is a warning sign and a ways
indicates that the circuit is over oaded. The fau t must a ways be repaired before the fuse is rep aced. If the
safety fuse is fau ty and needs rep acing after the unit is repaired, p ease make sure that you rep ace it on y
with the identica type and rating. NEVER use fuses of different ratings or cover fau ty fuses with a uminium foi .
This can cause fire and e ectric shocks and wi endanger your ife and the ives of others.
5. INSTALLATION