Ross Compressor Replica Kit

The Ross Compressor Replica Kit is a DIY effects project from General Guitar Gadgets that builds a replica of the vintage Ross Compressor, a compression pedal treasured by many players. The kit includes all the parts and materials needed to build one, including the PCB, and the maker describes it as priced at about what you would pay for a PCB and parts bought separately¹. It was announced on December 4, 2014, with JD Sleep of General Guitar Gadgets writing that it "Includes all the parts and PCB to build this great compressor"².

What the circuit is

The Ross Compressor was copied from the MXR Dyna Comp, and General Guitar Gadgets describes the Ross version as treasured by many players as being "the one" compressor³. The lineage runs both ways: JHS Pedals, describing its own Dyna Comp mod, notes that "we perform the exact same mods that Ross performed on the Dyna Comps of the 70s"⁴. In other words, the Ross was a Dyna Comp with changes made at the factory, and those changes are what the replica kit recreates.

The two circuits are close enough that General Guitar Gadgets sells them as one project: the maker states that the Ross Compressor Replica and the MXR Dyna Comp replica "either can be built on the same PCB or with the same Kit"¹. Aion FX, an independent builder of similar circuits, sums up the difference between the two originals: "It has better power supply filtering and thus lower noise, but is otherwise very similar to the Dyna Comp"⁵.

What is in the kit

• All parts needed to build the compressor, including the PCB²
• The CA3080 transconductance IC at the heart of the circuit¹
• 1N914 diodes and an LED for the circuit's clipping stages¹
• Instructions, version 2014December29¹

The maker describes the design as "the true and tested age-old design" and the result as "very nice sounding compression"². As with any DIY project, the sound you get depends on the build; comments and questions are welcome and can be sent to the maker by email¹.

Setting one up

The Ross-style compressor design uses a trimpot that needs adjusting once the pedal is built. Guitar FX Layouts, an independent technical analysis site, gives this procedure for a Ross-style compressor with Sustain, Tone, Ratio, Attack and Level controls: set Sustain full clockwise, Tone full counter-clockwise, Ratio full clockwise, Attack at noon, Level to taste, then turn the trimpot for the cleanest sound⁶.

Where the Ross name stands now

The Ross brand itself has a history that a builder of this kit may care about. Ross performed the same mods on the Dyna Comps of the 70s, and the circuit's lineage traces back to the MXR Dynacomp compressor, which the Ross Compressor was copied from⁴³.

For more on the effect itself, see Compressor Pedals.