Empirical Labs EL7X Fatso Stereo Audio Processor

Dial in some warmth to digital recordings with the FATSO's harmonic generation, soft clipping, low-pass filter, tape emulation and classic knee compression.

Empirical Labs' FATSO -- that stands for Full Analog Tape Simulator and Optimizer -- is more than just a 2-channel compressor. It adds warmth and saturation with a low-pass filter to round off the sharp edges, simulates the effect of old transformers and tape heads, and gently "soft-clips" peaks like saturated tubes or analog tape.

Get back what your digital recordings lack with the FATSO! With XLR and TRS I/O, this 2-channel analog device specializes in adding "musical non-linearities" to your signal with effects like harmonic generation and soft clipping, high-frequency saturation, transformer and tape head emulation, and knee compression.

The FATSO Goes to Eleven

ELEVEN is a compressor for the Fatso, replacing the old GP Ratio, and emulates the famous UREI 1176LN in 20:1, with the slowest attack, and fastest release. This 1176 setting has been used on countless hit records through the decades. With the slower "1176" attack, the transients keep the dynamics present, while the high ratio, can radically limit the dynamic range of any source, making it present and sitting in a nice little place in your mix. One can slam it, or just touch it with a few dB of compression. You will find it great on Vocals, Bass, acoustic guitars, drum room mikes, pianos etc.

The ELEVEN ratio took several months of experimentation, and required a rather radical attack mod to get close. It was one of those projects that Dave Derr, the designer, thought would only take a few days, but upon read more initial research and listening tests, subtleties emerged which required starting over several times. "I got in one of these design loops, where you would get one thing right, then change another parameter or component, and find that it changed the first thing you thought you had right. It was actually a long frustrating series of changes, that slowly spiraled towards the desired result. Any kind of math calculations or scaling seemed useless. In addition, while testing 1176's, I discovered issues that I'm quite sure were not intended by the original designers, and probably things of which they were not even aware. But using modern digital oscilloscopes and analyzers, along with digital workstations, and our good old ears, we could see artifacts that the original designers couldn't." "Heck, they may have even tried to fix the little imperfections that gave the 1176 its unique character, had they the tools to see them. Thank gosh they didn't, right?

Anyway, the design loop was frustrating, but like anything that takes you to unexpected places, hopefully you come out a little bit wiser, and with a great product. I hope our customers find the new ELEVEN ratio fun to use, and discover it can add some more magic to your music."

NOTE: ALL existing older "Fatso Jr's" can be modified to change the GP ratio to the new ELEVEN ratio. In addition, all Fatsos shipped from Empirical Labs since June 2013 have had the ELEVEN ratio already installed in the circuit, under the GP ratio, so if you bought a Fatso recently, you probably already have the equivalent EL7-X circuitry.

New Logic and Interface Operation

The original Fatso Jr could operate quite warm. Since heat is the enemy of reliability, we decided to do what we could to cool the unit down in this re-design. By replacing discrete logic with a microprocessor, and eliminating warm running and often unreliable display circuitry, the current draw was dropped over 20%, allowing the power supply and analog circuitry to benefit from a cooler running product.

The FATSO also has greatly improved interface operation. Holding any button in for a second will make the control step backwards, so the user doesn't have to cycle around to go back one step in setting one parameter. In addition, the Stereo Link is improved and offers a second link method by holding in both COMP buttons. It locks the compressors and Bypass logic together, and allows either channels' buttons to control the settings. Much more foolproof.

There is now a separate LED for the TRACK (Tracking) compressor, so that two LEDs do not have to be used, and interpreted by the user. SPANK is now a Blue LED delineated from the other compressors off to the side, to indicate that it is different and can be used in conjunction with the other ratios. Customers will find compressor selection more obvious and FUN.

Fatso's Four Types of Operation

- Harmonic Generation and Soft Clipper (Distortion Generation) -- this class A circuit gently rounds the peaks like saturated tubes or tape.

- High Frequency Saturation (Warmth) -- a one-of-a-kind dynamic low pass filter which softens high frequencies when they "pile up" on a source.

- Transformer & Tape Head Emulation -- a simulation of the effect of input and output transformers of older devices, which adds the low frequency harmonics that characterize them, as well as analog tape..

- Classic Knee Compression -- your typical automatic leveling device found on just about every instrument and vocal track as well as on the overall buss, done Empirical Labs compression -- smooth and sweet, but in your face!

Arguably the coolest and most unique device in the Empirical Labs arsenal, the FATSO (Full Analog Tape Simulator and Optimizer) is a digitally controlled analog device that gives musicians and engineers easy access to many of the desirable characteristics exhibited by older tube and Class A electronics and magnetic tape mediums. This two channel audio processor musically integrates frequencies and transients, increasing the apparent volume while keeping tight control over peak levels.

With the FATSO, recording studios and audio production facilities can enhance and soften the sound of Hardware Digital Recorders (HDRs) and Digital Audio Workstations (DAWs). Mix engineers will have the option not to have to use bulky, expensive analog tape recorders to get the warmth and sweet high end they've come to rely on for so many decades. Owners of DAWs and HDRs can finally put a stop to complaints about the coldness and brittle edge of their mixes and instruments. Even audiophiles can benefit from the FATSO, bringing back the warmth and ambience of LP's and tapes to their CD players and other digital reproduction mediums.

As with most Empirical Labs products, the unit is incredibly easy and fun to use. Large Distressor-style knobs control the input and output levels. Four meticulously tweaked compression modes - including the extremely popular "Buss" setting and the legendary "Spank", a subtle knee followed by hard limiting resembling the SSL talkback compressor - can be selected (and combined!) with the push of a button. Seven different high frequency saturation "Warmth" settings are accessed just as easily. The FATSO also features switchable transformer circuits, which can add the musical artifacts generated by classic devices like NEVE, API, etc such as low order clipping and inter-modular distortion, transient clipping... and some other very musical non-linearities. True to its name, the FATSO is rather sturdily constructed - you'll be impressed with how well built it feels when you first lift it out of the box.

The FATSO has been the "secret weapon" of studio and live engineers for many years, allowing them to add the elusive magic of vintage gear to their sound. Once you start using it, you'll never want to be without it!
read less

- Freq. Response is 2 Hz to 60 kHz in clean audio mode (+0, -3 dB).
- Dynamic Range 110 dB from maximum output (20%THDsoft clipping) to minimum output. Greater than 100 dB signal to noise.
- Distortion Ranges between .06% and 20% depending on mode and settings.
- DC coupled Input and Outputs
- High quality audio caps used internally. Compressor Time Constants - Attack range 1mS - 60mS. Release range .05 sec to 3.5 seconds. Attack and Releases are fixed by the compression type selected.
Dimensions and Weight in Packaging
Base Item
Shipping Weight: 12.5 lbs
Shipping Dimensions: 23 x 16 x 4 in
Manufacturer Part Number (MPN): EMP FATSO

For support or warranty questions, please contact the manufacturer:
Phone: 973-728-2425

Reviewers gave this product an overall rating of 5 out of 5 stars. (8 ratings)
Submitted May 2, 2004 by a customer from verizon.net


Overall: 5 out of 5 stars
(see rating details)
I will always own one till the day i die, become maimed, crippled or what ever ill probably be buried with it.
Very Quite and really warms up the signal. gets rid of the peircing highs on all of my tracks. Also the comressor especially Tracking is very very usefull. I would trade all my other compressors for this Including my 1176 and SSL Talkback.
All i have to say is with what other product can you get analog sound without running to tape. You get no tape noise and saved me thousands in tape costs.
Ive had mine for 3 years have taken it to shows and its been dropped kicked stepped on and still works perfectly.
THE ABSOLUTE BEST PIECE OF GEAR I OWN. 2300 is nothing to what it has saved me in tape and time.
Manufacturer Support
FREE FREE FREE Tech support is FREE Repairs are FREE and to have them look at it was FREE they replaved my knobs that i broke, my front panel that was bent, and my top cover that was beat to crap. All for free. they had it back to me in 2 days.
The Wow Factor
Very easy to use but i feel it needs more spicing up on the text and front panel.

Musical Style:

Hip hop,Reggae
27 of 30 people (90%) people found this review helpful. Did you?
Thanks for your opinion!


  • 18 x  
  • 12 x  
  • 8 x  
FREE -Day Shipping!
Get it  for
Get it by if you order within
Shipping to