Empress Effects ECM-519 compressor - Manual (Page 11)

Xformer Loading
The compressor is equipped with an output transformer that
can be switched in and out of the circuit.
Off: In this mode the unit runs with an electronically balanced
output. It is very clean and provides the largest bandwidth.
On: This inserts the output transformer in the circuit. It is pretty
clean sounding but you'll start to notice a smoothing of
transients providing a warmer top end, and a slightly thicker
low-mid from slight saturation in the low frequencies.
Loaded: In this mode the output transformer is loaded down so
it saturates easily. This really smoothes out the transients, and
provides a vintage feel. It's amazing for controlling cymbals in a
drum buss or for taming sibilance in vocals.
Tip: The transformer is at the very output of the unit. So if you'd
like to add the transformer sound without any compression, you
can run with completely dry mix to do this.
Tip 2: The Output control on the front panel also controls how
much level the transformer sees, so turning up the output will
provide more saturation.