UTA UNFa-1 User manual

UNFa-1 User Manual Version 1.0
UTA
UnderToneAudio
1. INTRODUCTION 2
2. SAFETY/POWERING UP 3
3. RACK MOUNTING 6
4. AUDIO CONNECTIONS 7
5. FRONT PANEL CONTROLS 8
6. EXPLANATION OF FEATURES 10
9. SPECIFICATIONS 13
1

1. INTRODUCTION
Congratulations! You are the proud owner of the UTA UNFa-1 UnFairchild Accessory unit that
adds a whole new world of control and exibility to the UnFairchild 670M mkII.
To get up and running right away with your UNFa-1, skip to Chapters 2 (Powering Up), 3
(Rack Mounting), and 4 (Front Panel Controls). The most vital information about the proper
installation of the UNFa-1 in this manual is in Chapter 3 (Rack Mounting). The rest of the
manual contains more detailed information that is not essential for understanding the
unit’s basic functionality.
The UNFa-1 is a collection of new features, some of which I always knew I wanted on the Un-
Fairchild and some of which I discovered I wanted on the UnFairchild after years of use. I always
knew I wanted a built in HP lter for the side chain and a WET/DRY mix control but there were
already so many new controls on the UnFairchild that I felt it was better to save them for an op-
tional add on. The WET/DRY mix requires adding an additional active gain stage that didn’t exist
on the original Fairchild and I felt permanently adding it to the original UnFairchild unit would
stray too far from the mission of faithfully recreating the integrity of the Fairchild circuit. These
additional feature would also drive the cost higher on a unit that is already on the very high end
of the world of high end audio gear. I didn’t want people paying for features that they might not
want or never use and were never on an original Fairchild.
The Feedback/Feed Forward blend control is something I discovered in my travels with the Un-
Fairchild 670M mkII as I explored using it on absolutely everything. It is by far my favorite of
the new features added with the UNFa-1. I was enjoying the incredibly aggressive compression
character you can achieve with the Feed Forward splitter cables but found that, at times, it was
dicult to nd a setting that wouldn’t over compress on some sections while under compressing
on others. I started experimenting with blending Feedback and Feed Forward externally on my
console. The results were immediately, massively satisfying but the setup was complicated and
cumbersome. I knew I wanted this feature to be more eortlessly available.
I realized that it was impossible to do Feed Forward compression at the same time as either of the
M/S modes. There were times when I needed to do this, so that is xed with the M/S mode switch
on the UNFa-1. There were times when the simple approach of“loudest channel takes over” ste-
reo linking was unforgiving when you have extreme dierences in the left/right source material.
The “AVG” mode addresses that issue.
I will get into detailed explanations and examples on how to apply all of these exciting new fea-
tures later in this manual!
-Eric Valentine
2

SAFETYINSTRUCTIONS

WARNING:Toreducetheriskoffireorelectricshock,donotexposethis
producttorainormoisture.

CAUTION:RISKOFELECTRICSHOCK.DONOTOPEN.Therearenouserserviceablepartsinside
theproduct.Referservicingtoqualifiedservicepersonnel.
Inordertoensuresafeoperationofthedevice,followtheseguidelines:
1. Readtheinstructionmanualinitsentiretybeforeoperatingtheequipment.Retainthe
manualforfuturereference.
2. Observeallsafetyprecautions,warningsandinstructionsnotedinthismanual.
3. Alwaysunplugthisdevicefromthewallsocketbeforecleaning.Useonlydrycloth.Do
notuseaerosolsorsolvents.
4. Keepthisdeviceawayfromsourcesofwatersuchaspools,bathtubsandsinks,anddo
notexposeittorainorsplashesofwater.Donotplaceobjectsfilledwithfluidonthe
device.
5. Ventsareprovidedforheatdissipationonthesidesandtherearofthedevice.Maintain
atleast2”(5cm)spacearoundtheseventstoprovidesufficientventilation.
6. Keepthedeviceawayfromsourcesofheatandopenflamesuchasheaters,radiators,
stoves,litcandles,etc..
7. Makesurethepowercordisintactbeforepluggingitintothedevice.Donotusecords
withvisibledamagetotheinsulationorconnectors.
8. Thisdeviceisequippedwithasafetyfeaturethatrequirestheuseofathreepin
groundingpowerplug.Donotdefeatthesafetypurposeofthegroundingplug.Ifthe
providedplugdoesnotfityouroutlet,consultanelectriciantoreplaceyourobsolete
poweroutlet.
9. Useonlyaccessorieslistedinthismanualorotherwisespecifiedbythemanufacturer.
10. Donotinstallthisproductoncartsorothermovingobjects.
11. Whenthedeviceisinuse,routethepowercordinsuchawaythatwillpreventitfrom
beingsteppedon,trippedon,pinchedordamaged.
2. SAFETY/POWERING UP
3

12. Donotusethisdevicewithwallorceilingmountsnotspecifiedbythemanufacturer.
13. TocompletelydisconnectthedevicefromtheACMains,disconnectthepowercord
fromtheACreceptacle.Foradditionalprotection,unplugthedeviceduringelectrical
storms,orwhennotusedforlongperiodsoftime.
14. Nouserserviceablepartsinside.Referservicingtoqualifiedpersonnel.Iftheunitwas
exposedtoliquid,excessiveheatorfire,orsustainedmechanicaldamageofanykind,
donotattempttooperateit.Disconnecttheunitfromthewalloutletandconsult
qualifiedservicepersonnel.

INSTRUCTIONSFOR220240VACOPERATION
1. Beforeproceeding,disconnectthepowercordfromtheACinlet.
2. ThisdeviceisprovidedwithapowercordforNorthAmerican110120VACoperation.
Foroperationinotherlocationsand/orfromothervoltagesources,usethecorrecttype
ofpowercordforyourareaandvoltagesource.
3. ThisdeviceisprovidedwithT0.4AACMainsfusesinstalledfor110120VACoperation,
andincludesT0.2Aaccessoryfusesfor220240VACoperationpackedseparately.Open
thefusedrawerontheACreceptacleontherearofthedeviceandreplacetheT0.4A
fusewiththeT0.2Aaccessoryfuse.
4. Inthefusedrawer,changetheACMainsswitchfromthe110Vpositiontothe240V
position.
5. Assurethatthefusedrawerissecuredclosedbeforeattachingthepowercord.

INSTRUCTIONSPOUR220240VACFONCTIONNEMENT
1. Avantdecommencer,débranchezlecordond'alimentationdelaprisesecteur.
2. Cetappareilestfourniavecuncordond'alimentationpourl'AmériqueduNord110
120VAC60Hz.Pouruneutilisationdansd'autresendroitset/oud'autressourcesde
tension,utiliserlebontypedecordond'alimentationdevotrerégionetsourcede
tension.
3. CetappareilestfourniavecT0.4AACMainsfusiblesinstalléspouruneopérationde
110120Vca,etcomprendT0.2Aaccessoiresfusiblespourunfonctionnement220
240VACemballésséparément.Ouvrezletiroirdufusiblesurlaprisesecteurà
l'arrièredel'appareiletremplacerlefusiblede0.4ATavecl'accessoirefusibleT
0.2A.
4. Dansletiroirdefusible,changerlessecteurCApasserdelaposition110Vàla
position240V.
5. Assurezvousqueletiroiràfusiblesestfixéferméavantdefixerlecordon
d'alimentation.
4
PCB

Before you connect the AC power cable, check to make sure the AC
operating voltage on the unit is set to properly match the voltage of
your AC outlets. The options are 110 V (appropriate for 110 V - 120 V
range) or 240 V (appropriate for 220 V - 240 V range). The operating
voltage of the UNFa-1 can be changed by removing the small tray in
the power entry module. Simply ip around the small PCB inside the
tray so the correct voltage is showing in the window when the tray is
re-inserted in the power entry module. When changing the UNFa-1 to
a dierent operating voltage, you must also change to the appropri-
ate fuse value to be sure it is either properly protected, or won’t im-
mediately blow the fuse (see Picture 1 or 2 for appropriate fuse values).
PLUGGING THE UNFa-1 INTO A 220 V- 240 V OUTLET WHEN SET
FOR 110 V OPERATION WILL LIKELY RESULT IN DAMAGE TO THE
POWER SUPPLY OF THE UNIT AND REQUIRE SENDING IT BACK TO
UTA FOR REPAIR!!!
Once you have conrmed that the operating voltage is set correctly,
make sure the power switch is in the “OFF”or “OUT” position. Plug
the supplied IEC AC power cable into the AC power receptacle on the
back of the unit. Plug the other end into an appropriate grounded
AC outlet. You are now ready to power up the unit. Simply push the
power switch on the front panel to the“ON” or “IN” position. When
the UNFa-1 is powered on you will see the the red LED illuminate. This
indicates that the UNFa-1 is powered up and ready for use.
The UNFa-1 is protected by a “slow blow” or time delay fuse. The fuse
can be found mounted in the removable tray (see Picture 3). There is
also a small compartment that holds a spare fuse. The spare fuse is a
T0.4A fuse for 110 V operation. If the UNFa-1 blows a fuse, it is best to
rst try to determine what caused the fuse to fail before installing the
spare. Once the cause for failure has been resolved, install the spare
fuse and you are ready to go!
Picture 1 shows the UNFa-1 set in the 110 V
mode. This will work for voltages from 110
V - 120 V
Picture 1
Picture 2
Picture 3
Picture 4
Picture 2 shows the UNFa-1 set in the 240
V mode. This will work for voltages from
220 V - 240 V
Picture 3 shows the fuse tray and the hid-
den spare fuse housing
Picture 4 shows the PCB
voltage selector
5
POWERING UP

3. RACK MOUNTING
The UNFa-1 is a Class A device. Class A circuitry unavoidably generates heat. How one chooses to rack-mount
these devices can have a signicant aect on the ambient temperature inside the enclosure. We have done
everything we can (short of using a fan) to improve the thermal performance and we have put them through
“worst case” rack mounting scenarios to make sure that they will perform reliably under those conditions.
WE STRONGLY RECOMMEND LEAVING A GAP BETWEEN THE UNFa-1 AND THE UNFAIRCHILD MOUNTED
IN A RACK TOGETHER. It will ensure longest possible healthy function of both devices.
6

4. AUDIO CONNECTIONS
REAR AUDIO INPUTS/OUTPUTS
XLR AUDIO INPUTS/OUTPUTS - Use these connectors as your main inputs and outputs for the UnFairchild
670M mkII. The DB25“UnFairchild Interconnect” snake will pass these signals on to the UnFairchild 670M mkII.
DB25 UNFAIRCHILD INTERCONNECT - Connect the DB25 end of the provided“UnFairchild Interconnect”
snake to the DB25 connector on the back of the UNFa-1 unit. All 8 of the XLR connectors on the other end of
the “UnFairchild Interconnect” snake needs to be plugged into the corresponding inputs and outputs on the
back of the UnFairchild 670M mkII unit.
(Back of UNFa-1)
(Back of UNF 670M II)
7
INPUT VOLTAGE:
110-120/220-240VAC,
60/50Hz
110V - T 0.4A
240V - T 0.2A
Maximum Power
Consumption 25W
Serial #
UnFairchild Interconnect
Model: UNFa-1
CAUTION
!
Voltage select in fuse drawer
MAINS FUSE: RISK OF ELECTRIC SHOCK
DO NOT OPEN
WARNING: SHOCK HAZARD - DO NOT OPEN
AVIS: RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR
R Ho S
2011/65/
E
U
INPUTS
LR LR
OUTPUTS

5. FRONT PANEL CONTROLS
8
MIXFB/FF HP FREQ
BYPASS
IN
OUT
IN
OUT
AVG
IND
M/S
UTA
UNFa -1
FB
16
8
404
8
12
16
FF
FB
16
12
8
40
8
12 12
16
FF
23
OFF
32
44
83 113
155
213
292
400
23
OFF
32
44
60 83 113
155
213
292
400
OUTPUT
-10 0
-9
-8
-7
-6 -5 -4
-3
-2
-1
-10 0
-9
-8
-7
-6 -5 -4
-3
-2
-1
WETDRY
16
12
8
404
8
12 12
16
WETDRY
16
8
404
8
12
16
460
1
52 3 6 7 8 4
DESCRIPTION OF FRONT PANEL CONTROLS
1. POWER SWITCH - This switch power the unit on and o
2. POWER LIGHT - This light is illuminated when the unit is powered on.
3. AVG,M/S,IND - These toggle switches add additional control for stereo linking and M/S modes. When
they are both in the down position, the UnFairchild can behave as two mono compressors. When the left
toggle is in the up position, the left and right signals are blended together and sent to both channels for
“Averaged”stereo linking (more about this on pg. 11). When the right toggle is in the up or “M/S” position
the feed forward signal is converted to M/S so you can do M/S compression on FF or blended side chain
signals. (More about this on pg. 12). The “SIDE CHAIN INSERT” toggle switches on the UnFairchild must
be turned on for these features to function.
4. FB/FF - These rotary switches control the blend between Feedback and Feed Forward signals going to
the side chain inputs. When the control is fully counterclockwise the side chain input will receive 100%
Feedback signal. When the control is turned fully clockwise the side chain input will receive 100% feed
forward signal. When the controls are in the 12 O’clock positions, the side chain input will receive equal
amounts of Feedback and Feed forward signals. The numbers indicate a dierence in volume. Each
step of the rotary switch adds 2dB of dierence in volume. For example, the “4” position in the clockwise
direction indicates that the “FF” signal will be 4 dB louder than the“FB” signal. The “SIDE CHAIN INSERT”
toggle switches on the UnFairchild must be turned on for these features to function.
5. HP FREQ - This rotary switch sets the high pass frequency for the side chain signal. In the fully coun-
terclockwise position there is no high pass ltering happening. As the knob is turned clockwise the high
pass frequency will get increasingly higher. The lter is 12dB/oct Butterworth lter at the frequencies in-
dicated by the marking on the panel. The “SIDE CHAIN INSERT” toggle switches on the UnFairchild must
be turned on for these features to function.

PANEL CONTROLS (CONTINUED)
6. MIX - This control allows you to blend the compressed signal with the original un-compressed signal.
The numbers indicate a dierence in volume. Each step of the rotary switch adds 2dB of dierence in
volume. For example, the “4” position in the clockwise direction indicates that the “WET” signal will be 4
dB louder than the “DRY” signal.
7. OUTPUT - This rotary switch allows you to reduce the output volume of the blended output signal
10dB in .5 dB steps. I have found that the UnFairchild can sound really good when pushing A LOT of level
through it. By reducing the output level, you can get the benets of pushing a lot of level without clip-
ping the input of whatever device comes after it.
8. BYPASS - These toggle switches allow you to bypass the MIX and OUTPUT processing done by the
UNFa-1. These bypass switches only bypass the processing done by the UNFa-1 and do NOT bypass the
processing done by the UnFairchild 670M mkII. If you want to bypass the compression entirely, you have
to use the bypass setting on the unFairchild itself. It is done this way so users can bypass all of the active
circuitry of the UNFa-1 and use the UnFairchild 670M mkII as it was originally designed.
9

6. EXPLANATION OF FEATURES
THE FB/FF CONTROL
We added the FB/FF control so you can get the full benets of applying Feed Forward (“FF”) compression
to the UnFairchild circuit. FF compression is a wonderfully aggressive sound but can be a bit unwieldy at times.
Being able to blend the Feed-Forward (“FF”) signal with the Feedback (“FB”) signal allows you to add just the right
amount to get that amazing aggressive sound without having the compression fall of a cli of over compressing.
If any of you have experimented with FF compression by using the included “Y” cables, you probably know that it
is a very extreme eect that can easily cause the compressor to sound like it is malfunctioning. Wildly over com-
pressing to the point where the signal is being cut o entirely. Blending in some of the FB signal eliminates that
issue. On more percussive signals like a drum mix, we have found that setting the control around 4 or 8 on the FB
side can give you some really great aggressive, grabby compression without freaking out too much. Lower set-
tings in the 12 to 16 range on the FB side, can be really great for overall mix buss compression if you want to hear
the compression eect more. Higher settings like 8 to 12 on the FF side can give really extreme drum compression
that isolates the transients and can be blended in with the mix control. It can serve as a “Transient Designer” type
eect.
THE HP FREQ CONTROL
This is pretty straight forward at this point. Many of you are likely already aware of the practice of High
Passing the side chain signal on a compressor. For those of us that like to have a lot of low end in our mixes, it is
helpful to make the compressor LESS sensitive to those frequencies so it is not mostly reacting to only the low fre-
quencies and pulling down the volume of the overall mix. The HP FREQ control allows you to control this issue. It
is really helpful when compressing a drum mix. If you like A LOT of kick drum in your drum mix and are compress-
ing the overall drum mix, the compressor will mostly just be compressing the kick drum hits and make it impos-
sible to maintain the level of the kick drum in the drum mix. Simply turn up the HP FREQ control to the 83 to 113
range until the compressor is equally compressing both the kick and snare in the mix. The same principal applies
to an overall mix buss but the setting is typically a little more subtle. Usually in the 44 to 60 range. If additional
processing of the side chain signal is needed, it is best to add it between the INSERT RCV snake XLRs and the Un-
Fairchild Insert Returns.
THE MIX CONTROL
This is also pretty straight forward at this point. Many of you are likely already aware of “parallel”compres-
sion. With parallel compression, you are blending the compressed signal with the original uncompressed signal in-
stead of only hearing the compressed signal. It allows you to use more extreme compression settings without hav-
ing the signal sound too compressed. Why is this useful? Why wouldn’t you just use a less extreme compression
setting if you want it to sound less compressed? Blending more extreme compression can sound very dierent
than simply setting the compressor less extreme. When compressors are imparting more signicant amounts of
compression (in the 15 - 20 dB range of gain reduction) you get more artifacts from the compression eect (distor-
tion, pumping, etc.) Sometimes these artifacts can be very desirable but make the source sound too compressed.
By blending in some of the uncompressed signal you restore the dynamics of the original source while keeping the
artifacts of the extreme compression setting. I like to apply this feature by starting with the mix control in the fully
clockwise position at 100% wet blend. I nd an extreme compression setting that has all of the desirable color-
ation I am looking for, then blend in some of the dry signal (by turning the mix control counter-clockwise) until
enough of the dynamics have been restored.
10

11
THE OUTPUT CONTROL
As mentioned in the “Front Panel Controls”section, we have found that the UnFairchild can sound really
good when pushing A LOT of level through it. By reducing the output level, you can get the benets of pushing a
lot of level without clipping the input of whatever device comes after it. The setting we generally use for this is to
turn the input gain on the UnFairchild all the way up (don’t be shy... This thing sounds great when it’s pushing a lot
of level). Then adjust the “Threshold”control for the desired amount of compression. If the resulting output level
is clipping the input of the following device (A/D converter, EQ, etc.) then simply turn down the output level with
the “OUTPUT” control on the UNFa-1 until you have the appropriate level.
Some of you may have noticed that under very extreme compression settings the right and left sides
can sound a little dierent even when stereo linked. This is due to the inherent limitations of the design utilizing
Vari-Mu tubes for the gain reduction. Dierences in the tolerances of the tubes can be more signicant when you
get deeper into the gain reduction curve of the tubes. The original Fairchild 670 did not even oer a stereo linked
mode, maybe for this reason. The issue can be compensated for by adjusting the bias current of each collection
of 4 tubes for the left and right sides. We are using the bias current adjustment as the“GAIN TRIM”control on the
UnFairchild (bias current also is a great way to adjust the overall level of a channel). With output level control on
the UNFa-1 you can now use the “GAIN TRIM” control on the UnFairchild to match the stereo compression for ex-
treme compression settings while maintaining the left/right balance of the two channels. If you are applying very
extreme compression on a sound source, let’s say a drum mix, and you hear the left and right sides not matching
perfectly, then listen to each side individually and determine which of the two sides sounds more compressed.
Turn up the UnFairchild “GAIN TRIM” control on the side that sounds more compressed by .5dB and then turn down
the “Output” control on the UNFa-1 .5dB (1 click) to match the level. Listen again and see if the two sides are better
matched. You can repeat again if the same side is still sounding too compressed.
THE AVG MODE
The “AVG” or “Average” mode oers a dierent way to achieve stereo linked compression. There are now 3
ways to have both channels compressing the stereo information the same or similar.
Original Link Mode - (UnFairchild set to Link, UNFa-1 “AVG” o or in the down position). If you only use the “Link”
mode on the UnFairchild than whatever channel (Left or Right) has the loudest signal will take over and trigger
compression on both channels. This is best when you want the compression to be more sensitive to signals that
are hard panned left or right. Signals that are hard panned will compress approximately 3dB more than if they are
panned to the center (depending on your “pan law” setting).
Link + AVG Mode - (UnFairchild set to Link, UNFa-1 “AVG” on or in the up position). With this combination of
settings, the left and right signals are summed to mono before being sent to the side chain. The result is that the
UnFairchild will compress more consistently regardless of where something is panned. The benet of this is that
hard panned signals will not excessively pull down the level of a whole mix.
IND + AVG Mode - (UnFairchild set to “IND”, UNFa-1 set to “AVG”). With this combination of settings, the identical
mono summed signal is being sent to both channels but the channels are not linked together. You can manually
set the UnFairchild for the best matching of left to right compression. The benet of this that occasionally the tol-
erances of the tubes make it dicult to electronically link the two channels together and have them match exactly
with extreme amounts of compression. With this setting you can simply match them by ear.

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THE M/S MODE
The M/S mode on the UNFa-1 simply makes it possible to do M/S compression with Feed Forward com-
pression. If you like Feed Forward compression and M/S processing the benets are obvious... You’re welcome. It
is important to know that both the UnFairchild AND the UNFa-1 need to be in M/S modes for this to work.
The M/S and AVG modes are mutually exclusive. When you engage the M/S mode the AVG mode is bypassed.

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8. SPECIFICATIONS
INPUT VOLTAGE 110-120/220-240 VAC, 60/50 Hz
MAINS FUSE
110V T 0.4 A
240V T 0.2 A
MAXIMUM POWER CONSUMPTION 25 W
INPUT IMPEDANCE
LINE INPUT 25K
OUTPUT IMPEDANCE
LINE OUT 47Ω
FREQUENCY RESPONSE
LINE IN/OUT 10 Hz - 50 kHz +0 /-1 dB
NOISE FLOOR
LINE IN/OUT -91 dBu (20 Hz - 20 kHz)
MAX LEVEL BEFORE CLIP
LINE IN/OUT +27 dBu (or better)
DISTORTION
LINE IN/OUT .005% at +27 dBu
DIMENSIONS
FRONT TO BACK 12.25”
(WITH HEAT SINKS and KNOBS) 14”
LEFT TO RIGHT 17.25”
(WITH RACK EARS) 19”
WEIGHT
ACTUAL 12 lbs
SHIPPING 15.8 lbs