Pete Cornish OC-1

The maker's core claim for the pedal is transparency: no change to frequency response, no distortion, and the absolute minimum of added noise¹. It carries three controls, Comp, Volume and Blend, and runs on a 9V DC supply.

How the OC-1 compresses

The OC-1 is a feed-forward design with what the maker calls a minimized two-stage audio signal path: an input buffer and an output make-up gain stage, with a light-controlled variable attenuator driven by the side chain². In an independent circuit trace published in 2019, Aion FX found the classic Cornish buffer followed by a three-way split into the compressed path, a clean path for blending, and a sidechain peak detector⁴.

Aion FX's trace describes the compression itself as a simple voltage-dividing attenuator, formed by a resistor and the LDR (light-dependent resistor) portion of a vactrol, essentially a dynamically operated volume reduction⁴. They note that this method of volume reduction is the same type used in the first optical compressors of the 1950s, such as the LA2A⁴. The sidechain turns the audio signal into a control current that illuminates the LED in the vactrol, a topology Aion FX reported they had not seen before⁴.

The controls: Comp, Volume and Blend

Aion FX's trace adds two practical notes on how the controls interact. The volume and blend controls are somewhat interactive, so the volume may need to be backed off when blended signal is added to keep a constant level. And the volume control's minimum position is unity rather than zero volume, because it is an op-amp gain stage rather than a traditional volume knob at the end of the circuit⁴.

Power and connections

The OC-1 has no battery input; it is powered through an input for a 9V DC supply². The adapter should be noise free and fully stabilized at 9V DC, capable of supplying 20mA. The coax connector is 5.5/2.1mm with the center pin negative².

Connections are straightforward: guitar to the OC-1 INPUT using screened cable, and the OC-1 OUTPUT to your amp input using screened cable².

An original design from Pete Cornish

Pete Cornish describes the OC-1 as a completely original design, not copied from any previous or current device, and notes it was introduced in common with the recently introduced CC-1, a compressor with active three-band EQ². Aion FX's independent trace backed the claim: their X-ray examination of the circuit, which was covered in thick epoxy, was enough to tell them the OC-1 was in fact an original design, not quite like anything else they had seen⁴.

The OC-1's own approach differs from the CC-1's: where the CC-1 offers active Bass, Middle and Treble bands that are completely independent, the OC-1 has no tone controls at all, consistent with the maker's claim of no change to frequency response⁶¹.

Each unit is hand built, wired and tested by Pete, Lynda and Mingus Cornish². The pedal carries a two-year warranty from date of purchase covering original manufacturing faults, with normal wear, misuse, unauthorized modifications and accidental damage excepted; the warranty is voided if the guarantee labels are damaged or removed, and it is not transferable².

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