Alesis 3630 Stereo Compressor


Out of stock


The 3630 has become a bit of a legend due to its unsubtlety, alleged poor sound quality and its capacity to provide vicious pumping compression

I bought a couple to modify to see if they could be improved.  Do they sound bad?  No – they sound like pretty much any other VCA-based compressor when they’re not working hard. Do they sound good? That depends on your definition of good

I found they are difficult to set up and very critical of threshold and attack times. Once set correctly they are very effective, and once set to pump like crazy they produce a wonderful squashed sound which is fantastic added to the original sound (aka parallel compression)

The sidechain input means it’s easy to pump the compressors using an external key signal. Typically that’d be a short sample like a woodblock driven by a sequence in your DAW

The late-model Rev D 3630s (like the one in this auction) had better Op-Amps and VCAs (THAT 2252s) than the early ones and it’s a big job to improve on those components. One area where they can be improved is the power supply

Alesis typically used puny capacitors for the power supply board. I’ve replaced the psu capacitors with 1800 uF, 25 Volt, high-spec Panasonic caps. I’ve also decoupled the rectifier diodes & voltage regulators and provided a better earth for the inputs & outputs

The 3630 uses an external 9 Volt AC power supply which is bumped up to ± 15 Volts by the internal power supply board. To get the best out of the modifications I supply a new, higher-current external power supply with each compressor

In this auction • Modified Alesis 3630 compressor with internal power supply & earthing modifications • New upgraded 2 Amp external power supply

VCA compressor using dbx or THAT VCAs. Inputs and outputs are unbalanced on jack sockets. Power supply is via an external 9 VAC power supply
1U device suitable for mounting in a standard 19" rack
Owners manual
Twenty Best Compressors of All Time Review
Excellent used condition