Instruction Manual
UAD Powered Plug-Ins Manual - 222 - Chapter 18: Empirical Labs EL7 FATSO
FATSO Screenshots 
FATSO Functional Overview
Four Processing 
Types
The FATSO was essentially designed to integrate frequencies in a musical 
manner and provide some foolproof vintage sounding compression. Gener-
ally, it is difficult to make the unit sound unnatural due to its vintage topology. 
FATSO provides four types of processing.
Saturation and 
Distortion 
Processor
Harmonic Generation & Soft Clipper
Basically, this is a distortion generator associated with the Input knobs. Any-
time you pass a signal through the FATSO, it passes through this part except 
in bypass. This processing is useful to softly but instantly clip peaks and tran-
sients, allowing a higher average level. Aggressive distortion can also be 
achieved through the same controls.
It is well known that the triode distortion in tube circuits produces lots of 2nd 
order and 3rd order harmonics, in somewhat varying ratios. Analog tape 
also saturates in this manner. The 3rd order harmonic is induced in the 
FATSO by increasing the level through two discrete distortion circuits and is 
usually the result of flattening the tops and bottoms of waveforms. Second or-
der harmonics are also added especially while compressing in the FATSO. 
The FATSO’s input clipping will give you the same result. These lower order 
harmonics form “the octave” and “the octave and a fifth” to the fundamental 
musical tones. They are actually “musical” distortion. Harmonics above the 
Figure 80. The FATSO Jr. plug-in window
Figure 81. The FATSO Sr. plug-in window










