Compton compressor/limiter

Compton is the result of a long collaboration between Kyle Rasmussen of Vitriol and myself.

Kyle asked if we could do a compressor designed with metal in mind, which requires A LOT of care
and consideration with this type of effect.
After a number of failures and a lot of thought, I decided to try the THAT4305 dynamics
processor I’ve used in my Ball Gag gate forever. THAT Corp has a wealth of information
available in their technical documents and engineering support, both of which came in clutch.

That being said, this is no copy of a datasheet, and an embarrassing amount of work went into
its design.

The result is an incredibly low-noise and frequency transparent compressor that’s so versatile it’s replacing some boosts on my board. I’ve started to use it as an always-on pedal, which makes playing easier, adds note clarity in complex chords, and makes fast passages sound clearer.

It has many of the advantages of running an overdrive, with better compression control, lower
noise, and no change in tone. I’ve been somewhat shocked at how much I like it in the place of a traditional boost for amps I inherently like their tone.

Compton also features selectable settings, and a switchable clean blend. Both features can be
controlled with external TRS switching.

Top row controls
CLEAN BLEND – This control adds your unaltered dry tone back into the compressed signal via a lossless mixing circuit. This is only engaged when the Blend LED (blue) is lit, which can be done via the Blend footswitch or through an external TRS switcher (explained later)
At minimum, the output will be 100% the output of the compressor. At maximum, there is no
contribution of the compressor circuit and therefore the output is completely unaffected.

THRESHOLD – Threshold sets the signal level at which the compressor starts to do it’s job. In other words, this control tells the compressor WHEN to work.

At minimum, the threshold is lowest and therefore will engage compression at lower signal levels.

At maximum, the threshold is highest and therefore will require higher signal levels to activate the compression circuit.

To help simplify setting this control, the indicator LED for the BYPASS footswitch is bicolor, with
each color indicating if the pedal is compressing or if it is allowing signal through without actively
compressing. RED = compressing, GREEN = not compressing.

Simple!

COMPRESSION – Even for the unfamiliar, this control is very intuitive. Compared to the threshold control, Compression sets how much the signal is turned down when it exceeds the strength as set by the threshold. Comparatively, this control tells the compressor HOW HARD to work.

At minimum settings, the compressor does not limit the signal strength. As Compression is
increased, the compressor works harder and more aggressively limits (“turns down”) the signal
once exceeding the threshold.

For those in tune with compressors, this control works as a “ratio” control. At minimum
Compression setting, the ratio is 1:1. At maximum Compression setting, the ratio is ∞:1.

Not too bad, right?

GAIN – This control serves as an output level compensation, partially to address any possible loss in signal strength from the pedal doing its job…but also to allow the player to use this to boost the input of his or her amplifier.

There’s no need to overthink this – you can treat it like the volume control for the pedal.

At minimum, there is approximately -15dB in gain, at maximum there is approximately +15dB in
gain. Note, though, that is interactive with any signal strength reduction from the compression
circuit.

Bottom row controls
THRESHOLD – as above

COMPRESSION – as above

GAIN – as previously described

Note – the bottom row controls are only active when the A/B LED indicator (yellow) is lit. These
controls can be engaged via the A/B footswitch or through an external TRS switcher.

Switching and feature utilization
As mentioned, you can engage the Clean Blend control, or the bottom row of compressor
controls with their corresponding footswitch OR through the use of an external TRS switcher.

Footswitch use:
Blend – pressing turns the Clean Blend control on (lit blue) or off (unlit)

A/B – pressing engages the top Threshold, Compression, Gain controls (led unlit) or bottom row (lit yellow)

External TRS switcher:
Connect a ¼” TRS cable into the EXT jack. A/B is assigned to tip, and BLEND is assigned to
sleeve. Set your external switcher to connect tip to ground/sleeve to engage the bottom row of
controls. Set your external switcher to connect ring to ground/sleeve to engage the clean
blend.

Even when using an external TRS switcher, the LEDS will still function as normal to help verify what the hell is going on