How to use a FET compressor: input, output and the knobs that run backwards

Short answer: turn INPUT up until the meter shows the amount of gain reduction you want, then turn OUTPUT down to match the level you started with. Pick a ratio (4 is the safe default), and remember that ATTACK and RELEASE get faster as you turn them clockwise. That is the whole routine.

A FET compressor is the fastest, most aggressive classic compressor design. It is the box engineers reach for when a vocal has to sit in front, a snare has to crack or a room mic has to explode. It is also the compressor that confuses people most, because it breaks the rules every other compressor follows.

There is no threshold knob

Most compressors have a threshold: the level above which compression starts. A FET compressor has a fixed threshold instead, and you push the signal into it with INPUT. More input means more compression. OUTPUT then sets the level that leaves the unit, so it works as makeup gain.

This feels odd for a minute and then becomes the fastest way to work: one knob for "how much", one knob for "how loud".

The one-minute routine

1. Set the meter to GR so the needle shows gain reduction.
2. Raise INPUT while the track plays until the needle swings back 3 to 6 dB on the loud parts. That is a typical amount for vocals and bass.
3. Lower OUTPUT until bypassing the plug-in no longer changes the loudness. Now you are judging tone, not volume. In PINCH-76, AUTO GAIN does this step for you.
4. Adjust ATTACK and RELEASE by ear (see below), then fine-tune INPUT.

The knobs run backwards

On a FET compressor, ATTACK and RELEASE get faster as you turn them clockwise. Position 7 is the fastest, position 1 the slowest. Almost everyone gets this wrong at first and turns the knob the wrong way when a sound is too squashed.

The ranges are also unusual. Attack runs from about 20 microseconds to 800 microseconds, so even the slowest setting is quicker than most compressors' fastest. Release runs from about 50 milliseconds to just over a second and changes with the music. Read attack and release, explained by ear for a full walk-through.

The ratio moves the threshold

PINCH-76 has four ratio keys: 4, 8, 12 and 20 (on the AE revision: 2, 4, 8 and 20). Higher ratios squash harder above the threshold, as on any compressor, and you can latch several keys at once.

The catch: on this design, each ratio key has its own threshold and knee. On the classic hardware the higher ratios start compressing later, so at the same INPUT setting 20:1 can show less gain reduction than 4:1. PINCH-76 calibrates every key, and every combination of keys, separately in the same spirit. When you change the ratio, look at the meter again and re-set INPUT. This one detail explains most "the ratio does nothing" complaints.

How much gain reduction is right?

There is no single answer, but most sources land in a familiar range. These numbers come from the recipes in the PINCH-76 user manual.

Starting points by source

Source	Revision	Ratio	Attack	Release	Gain reduction
Lead vocal	Rev D (LN)	4	3	5	3 to 6 dB
Bass DI	Rev D (LN)	8	2	3	4 to 6 dB
Snare	Rev F	8	3	6	4 to 8 dB
Room mics	Rev A	All	7	7	10 to 20 dB
Drum bus, parallel	Rev D (LN)	4	2	6	6 to 10 dB, MIX 35 %
Mix bus	AE	4	2	5	1 to 3 dB

Each line is a factory preset or a manual recipe in PINCH-76, so you can load it and adjust instead of starting from zero.

Questions

Why does my sound get louder when I add compression? Because you raised INPUT. Lower OUTPUT by the same amount, or switch on AUTO GAIN, before you decide if it sounds better.

Which revision should I start with? Rev D (LN) is the clean all-rounder. Rev A adds grit, Rev F adds bite, AE is the softest. See which revision for which job.

Can I use it just for colour? Yes. With ATTACK set to OFF, PINCH-76 stops compressing but keeps the sound of its amplifier and transformer.