Empirical Labs FATSO

The FATSO acronym stands for Full Analog Tape Simulator and Optimizer. However, that only partially describes the effects and features offered by this 4/01/2001 8:00 AM Eastern

The FATSO acronym stands for Full Analog Tape Simulator andOptimizer. However, that only partially describes the effects andfeatures offered by this unique piece of audio gear.

Designed by Dave Derr, FATSO is the latest product offering fromhis company, Empirical Labs, manufacturers of the well-known EL-8Distressor, a favorite of many producers and engineers. It's myfirst choice in several situations that call for the use of acompressor.

After months of hearing rumors floating around the industryconcerning FATSO, it was with great anticipation that I receivedone of the first production units for review.


The EL-7, as the FATSO has been designated, is a 2-channel,digitally controlled, analog signal processor, capable of stereo ordual-mono operation. The front panel has four large, calibratedknobs that go up to 10 — not quite Spinal Tap, but veryclose. Two of the gray knobs are used for Input Level and two forOutput Level control. Three buttons per channel (the CompressionSelector switch, the Warmth/Link switch and the Tranny/Bypassswitch) and a host of LEDs for metering and status indicationcompletes the package.

Inputs and outputs are via XLR or ¼-inch TRS jacks, withthe XLRs differentially balanced on the inputs and outputs and the¼-inch jacks balanced on the inputs as well. Pin 2 is wired“hot” on the XLRs and is user-changeable to Pin 3 frominside the unit. The owner's manual makes a point of stressing thatthe unused pin of a single-ended XLR output cable should be“floated” rather than tied to ground to preventshorting out any of the output amps. I checked with the factoryabout this, as many potential owners of the unit may useoff-the-shelf cabling for their wiring needs. In many instances,pre-wired XLR to ¼-inch cables have the unused XLR pin tied toground on the minus side. This is true especially if they are ofthe unbalanced, two-conductor, musical instrument-type. Themanufacturer replied that this would only present a problem if acombination of XLR and ¼-inch jacks were used simultaneously.In case of doubt, Empirical Labs offers optional (correctlyconfigured) XLR to ¼-inch adapter cables.

No digital inputs/outputs are provided, even though the targetedmarket is obviously the DAW, MDM and hard disk recordingcontingency. I thought about this for a while and decided it was agood thing. Because this is an analog processor, you'd eventuallyhave to convert your digital signal to analog to use this unit,anyway. If Empirical Labs had included an AES or S/PDIF provision,then not only would the price increase, but you'd be forced to usetheir converters, however good or bad they were, instead of theconverters you already own and love. This way just saves you adecision and a step. If you don't want to ever leave the digitaldomain, then this is probably not the unit for you at mixdown, butit certainly could be helpful during tracking sessions.

A Link/Sidechain input and individual channel inserts are alsoprovided via ¼-inch jacks. The power cord is the IEC-removabletype, and an internal switch can change the operating voltage from110 to 220 VAC.


The one-rackspace unit is solidly built, and the quality,craftsmanship and heft of the box will be immediately apparent.But, after all initial impressions are expressed and descriptionsof its physical layout are noted, two burning questions about FATSOstill remain: What the heck does this thing do, and how does itsound while doing it?

What it does is not an easy question. The short version is thatit emulates the characteristics of an analog tape machine whenmixing and/or tracking digital signals to help“warm-up” their sound. Unfortunately, these days,“warm” is probably the most overused term for defininga desirable characteristic pertaining to a piece of audio gear.

A better — albeit longer — answer requiresdescribing the types of processing the FATSO has on-board, whilenoting that they can be used individually or in combination. Ohyeah, it sounds so sweet when performing all of these functions, aswell.

The first process the FATSO offers is Harmonic Generation/SoftClipping or Distortion Generation. This produces continuouslycontrollable second- and third-order harmonics, which, when addedto the signal, provide a richer, fuller sound. There is also anapparent increase in volume without an increase in level.

Many software plug-ins try to achieve this effect in the digitaldomain. However, the ones I've tried usually sound like they arejust overloading the system's electronics to unusable (andunlistenable) proportions. I find that this happens no matter howmuch its GUI looks like the controls of an analog tape machine.

Without giving away any of his design secrets, Derr stated thatdigital processing cannot be used effectively when creatingclipping and distortion generation for frequencies above 3 kHzwithout a byproduct of unpleasant artifacts. He believes that onlyif current sampling frequencies are greatly increased will digitalsignals ever hope to rival the resolution that can be achieved forthose purposes in the analog domain.

The FATSO, however, does this job so nicely that once you patchit in and tweak it up, you'll have a hard time ever taking it outof the chain.

The unit does add distortion to the signal, but it is perceivedas harmonics — not as overload. The second harmonic generatedis the equivalent of an octave above the fundamental tone or pitch,and the third harmonic is a fifth above that. This process addsbody and clarity to the mids, while “tightening up” thebottom, which is especially noticeable on smaller speaker systems.The bass will seem more defined, and, generally, the otherinstruments and vocals will be more “in your face.”

Of course, this effect, like all the processing in the unit, isa bit like hot sauce; a little goes a long way, and too much willkill the taste of what you are cooking up.

The Harmonics and Soft Clipping are always in the signal path,unless the unit is bypassed. The effect is controlled by the amountof input level the FATSO gets, as adjusted by Input Level pots.This may be a problem for some users. You always get the effectwhen you put anything through the box. Because that is the mainpurpose of the FATSO, I don't have a problem with the setup. Still,be aware that this is the case when using the device.


Four types of compression, with seven possible combinations, areserved up next. These have fixed-time constants and ratios, and theamount of gain reduction is, again, dependent upon the input level.The compression, however, can be bypassed from the circuitry withthe Compression Selector switch. Two LEDs on the front panel ofeach channel indicate the “0 VU” and“Pinned” status of the FATSO. These can facilitatesetting the input levels for the Compressor, Harmonics Generatorand Soft Clipping processes.

The manual notes that if compression is being used, then itshould be the first process set up. The rest of the unit'sfunctions should be adjusted relative to the compressor's settings.I found this to be critical.

The compression has that famous Empirical Labs quality, onlywithout the more extensive control of the Distressor. But, if youuse one of FATSO's compressors carefully and gently, the parametersthat you've chosen work just fine for both tracking and mixing.

The four types of compression start with the “Bus”mode. If the FATSO consisted of only this compressor and theHarmonics/Soft Clipping Generator, then I still would have beensold on the thing. When placed across the stereo bus of a mixer oron playback of a 2-track source, you can't help but smile. I foundmaterial I previously mixed with a bit of low-end boost could beremixed through the FATSO, without the low EQ, and have a fatter,tighter bottom.

The “Bus” compressor is designed to emulate an SSLStereo Bus compressor and, when used gently, does a nice job oftransparently pushing up your level a tad, without pumping or othernasty side effects.

The “General Purpose” compressor is the next type upon the menu. Having a little faster attack, I found it a bitheavy-handed for the stereo mix, but nice for printing tracks— sort of like a dbx 160X.

The “Tracking Compressor” is meant to emulate an1176 and does a good job. This sound is the closest that FATSOcomes to matching the Distressor. With its controls set for fastattack and release times, I found this setting the most useful ofthe compressors for individual instruments.

Finally, “Spank” is a high-ratio compressor/limiterhaving the characteristics of the compressor on an SSL talk-backmic, but with full bandwidth and better overall specs. It has an“over the top” sound when hit hard by a signal. Spankcan be used alone or as a peak limiter following any of the othercompressors.

The Compressor Selection switch cycles between the differentcompressor types, allowing one switch to choose any of the fourcompressor types individually, or to select Spank along with one ofthe other three in series. It also can bypass all of thecompression. Distressor users will be familiar with this type ofmultiplexed switching.

The “Warmth” (there's that word again) processing isan interesting and unique function. Its control steps through eightstages, starting with off, then, as marked by LED indicators, fromone to seven. Each degree of added Warmth causes more gainreduction, from a frequency-dependent limiter with a lightning-fastattack and release. The filter controlling the response of theprocess is carefully designed to lop off only the highest,shrillest frequencies very quickly and recover just as fast. Whenused judiciously, this truly mimics analog tape saturation andself-erasure. Most of the frequencies affected by the Warmthprocess are above 10 kHz. This helps tame “spitty”vocals, harsh, edgy cymbals, overly bright guitars, trashytambourines and other signals that may not respond well to thedigital recording medium.

The Warmth control and the compressors are heavily interactive,so, again, the compression should be set up first when using theseprocesses together.

Both FATSO channels can be linked for stereo, or multiple unitscan link together for 5.1 mixes. Unlike most other stereo units,the inputs and outputs on each channel are still individuallyadjustable. This allows tweaking the levels on both channelsindependently. However, to maintain good stereo imaging, the Inputand Output Control settings on both sides should be matched.


The final FATSO process involves an actual iron and coiled wiretransformer, known as the Tranny. This transformer is unlike thoseused on older (and some current) tube and Class-A gear to isolateand impedance-match the inputs and outputs of equipment. Theyimparted their coloration on the sound of the gear,unintentionally, by being a necessary evil in the circuit. TheTranny process is intentionally designed to add certaincharacteristics to the sound. In a nutshell, it adds a midrangebite while it softens transients and tightens up, yet increases theapparent loudness, of the bottom.

The Tranny/Bypass Control switch is used to toggle the Trannyin/out of the signal path. This may be a point of contention forsome people. In order to fit everything on the front faceplate ofthe unit and still use the same type of switches throughout, theTranny shares control buttons with the Bypass function. So, whenusing the true, hard-wired, relay-controlled Bypass on the box, onemust first switch through the Tranny function, if it is notengaged. If returning to the Tranny from a Bypass condition, thenanother two taps of the switch are required. The same system ofmultiplexing and cycling used on the other control buttons isemployed, but instead of moving through two steps of the samefunction, it steps through two separate functions. I got used tothis and it is no big deal, but some may find this a weak spot onthe FATSO.

The manual suggests a test for the Tranny process that is fun totry and will impress your friends, family, clients and pets. Send a40Hz sine wave through the unit, and match the levels with andwithout the Tranny bypassed. Now, pull out those Auratones, or anyother little speakers you've got, and monitor the tone without theTranny engaged on those guys. Then kick in the Tranny process. Iwon't give away the results.

A few clever tips are mentioned in the manual, as well, whichonly add to the versatility of the unit. By inserting a device withlevel-controlling abilities in the insert point of a channel, youcan raise or lower FATSO's threshold by changing the level of theinserted device. When you add gain at the insert, the threshold ofthe unit is lowered and the amount of distortion produced is less.The opposite holds true when the gain at the insert is lowered. Ofcourse, the inserts can be used in the regular manner, too, to addan EQ or some other device in the chain.

Sidechain processing is also available using the link outputs tosend signal to an equalizer and returning the EQ's outputs to thelink inputs of the same channel.

During mixdown, a good way to use the device is to set FATSOacross the stereo bus before any other EQ, compression or effectsare added to the individual tracks. You'll probably use less signalprocessing that way: FATSO becomes a sort of Exciter in reverse,adding honey to your mix.

The Compressor types have been designed with“headers,” which permit different value components tobe swapped with the existing ones in the FATSO. These will allowthe control of the time constants, ratio, threshold and othercharacteristics of the compressor to be changed and/orcustom-modified in the future as they are offered.

At $2,499, the FATSO should be considered by users of digitalaudio systems — DASH, DAWs or MDMs — who want theperfect unit-to-track through and for use across the stereo bus atmixdown. Analog audio users will find this another quality tool fortheir arsenal. Anyone who has longed for a 1-inch, analog, 2-trackmachine should check out a FATSO, as well.

Empirical Labs, dist. in the U.S. by Wave Distribution, 1170Greenwood Lake Turnpike, Ringwood, NJ 07456; 973/728-2425; fax973/728-2931; or

Bob Buontempo is a freelance engineer, producer and writer basedin the New York City area. His new goal in life is to make enoughmoney to eventually put himself in a good nursing home. You cancontact him, harass him or donate to his cause by e-mail