Full Analog Tape Simulator and Optimizer

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.

The EL7X (shown above) is the next generation of the EL7 Fatso Jr. The original EL7 is no longer in production, however, they can be updated to the EL7X. Click here for more information.

The FATSO Goes to Eleven

ELEVEN is a new 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. Click here to find out how to upgrade your EL7 to an EL7X.

Four Types of Processing

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!

Universal Audio's FATSO Emulation

Endorsed and scrutinized for accuracy by designer Dave Derr of Empirical Labs, Universal Audio has painstakingly recreated the FATSO Jr. in this highly anticipated UAD Powered Plugin, capturing the sonic nuances of the original hardware. As part of the FATSO Powered Plugin, UA has also worked closely with Dave Derr to model the original concept of the FATSO, the FATSO Sr., with attack, release, and threshold compressor controls, among other features not available elsewhere.

Dimensions: 6.1″ x 2.8″

EL-FTC FATSO Threshold Controller

Expand the range of your FATSO and fine-tune the relationship between the Compression and Saturation circuits with the EL-FTC FATSO Threshold Controller. The EL-FTC plugs directly into the Sidechain Inserts on the back of the FATSO, giving you instant access to a world of tonal possibilities.

Click the link below to find a dealer:


  • Frequency Response – 2 Hz to 60 kHz in clean audio mode (+0, -3 dB).
  • Dynamic Range – 110 dB from maximum output (20 %THD soft clipping) to minimum output. Greater than 100 dB signal to noise.
  • Distortion – Ranges between .06% and 20% depending on mode and settings.
  • I/O – DC Coupled input and outputs.
  • Compressor Time Constants – Attack range 1ms – 60ms. Release range .05sec – 3.5 seconds. Attack and Releases are fixed by the compression type selected.
  • Power Consumption – 15 Watts Max.
  • Metal Chassis – single height 1.75″ high, 10″ deep, 19″ wide.
  • Shipping info – Box dimensions 22.5″ x 18.5″ x 3 1/4″.


for existing FATSO Jr. owners

Bronze Upgrade


The ELEVEN ratio
Four new compressor headers
Power transformer test and replacement (if necessary)
New EL7X Metal Front Panel
Two new front panel PCBs (lower power consumption)

Silver Upgrade


The ELEVEN ratio
Four new compressor headers
Power transformer test and replacement (if necessary)
New EL7X Metal Front Panel
Two new front panel PCBs (lower power consumption)

All upgrades include a 24-hour burn in, full QC and unit test for the latest specifications, and free shipping back within the continental United States.


You can alter the standard thresholds of the FATSO by inserting a level control in the Sidechain point. By turning the gain down there, the threshold will move higher, elevating operating distortion. Adding gain there will lower the threshold and lower Distortion/Saturation. Find your nearest retailer: https://wavedistro.com/dealers/

It is also possible to make the FATSO have frequency dependent compression using the Sidechain insert Jack (was previously labeled INSERT on older FATSOs). Send the tip of the Sidechain jack to an EQ, and return EQ to the ring. The sidechain must not have appreciable delay nor be out of phase since it will affect the response time and possibly comb filter the control signals when in Stereo.

Unlike the older units, the FATSO is uniform and predictable from one unit to the next. Precise factory calibration assures that if you go from one FATSO to the next, these settings will all sound the same. The only big variable is the input and output pots, which is why we use high resolution knobs, for recall. Differences in the new X version and the Older FATSOs The FATSO Jr was redesigned to lower power consumption and heat, as well as make the interface operate more like it was originally envisioned. The controls can now step backwards one setting by holding the associated button for less than a second. This enables the Bypass to be accessed with one button press from any state, as well as compare compressor and WARMTH settings more easily.

A “soft knee” is a compression curve where the first few dB of gain reduction occur at very low ratios, gradually increasing as the signal increases (gets louder). This makes the onset of compression very hard to detect. The knee usually extends for a few dB and gradually flattens out toward a final ratio. All the FATSO compressor types have dominant knees except for SPANK. The BUSS Type Compressor has a knee that can be as long as 15 dB, It was setup for 3 – 5dB to sound HOT like tape.

Place the FATSO at the output of your mixer before your power amps to level and fatten up the whole show. The BUSS compressor can level out volume differences while keeping the “smack” intact. Some house engineers use more aggressive FATSO compressors. The TRANNY may help on smaller systems to get the low freqs clearer, but it does gently roll off subsonic content, whereas many venues want to “show off” subs below 40Hz. There are dozens of clubs around the world warming their House PA systems with FATSOs.

By placing the FATSO immediately before a digital mixdown recorder such as a Hard Disk, RAM, or CD recorder, you should be able to get the sweet high end and low frequency fatness that you would get mixing to an analog tape recorder. Compression should usually be the BUSS type, use the warmth to soften the high end and the TRANNY to add some definition and warm harmonics to the low frequencies.

You really need several of each! Actually there is only a little in common between the two units. If you need a fully controllable compressor, that sounds like it has tubes and can emulate some famous older compressors, get the Distressor. If you do a lot of work in the digital domain and miss some of the smooth round bottom and softened high end of analog tape recordings, get the FATSO Jr. The FATSO does have some kick butt compressors in it but they are not fully adjustable. The Fatso was really intended to help get a good analog tape sound without analog tape… we just happened to have enough room to put in some really good compressors too.


Magazine Reviews


“People used to have to hunt for old, expensive gear to get the kind of sounds that the FATSO gives me.”
Ed Cherney
Lenny Kravits, Dave Matthews, Eric Clapton, etc.
“The winner of the highly-coveted, 'I’m going to write you a check right after the show' award was picked up by Empirical Labs for its FATSO processor”
Craig Anderton
Pro Sound News
“The kick drum chain was pretty complex, and on the bass and keys, I used a variety of the old compressors, as well as six Fatso compressors chained together for the surround mix and the SSL console compressor for the 2-channel mix. They sound great; they are clean and variable and dynamic.”
Kevin Shirley
Using the FATSO for Led Zepplin's 5.1 Live DVD
“In a word, the FATSO is a very good answer to what a lot of people loathe about digital recording. It smooths out the sharp, brittle edges to exactly the extent you choose, and fills in the hairline cracks just right. I use one on almost every mix I do. I could easily use one and quite possibly two more.”
George Massenburg
Journey, Toto, Earth, etc.

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