Boss CS-3 Compressor Monte Allums Opto Mod Review

Being a single-coil player, I always find it more comfortable to have at least slight compression on when I perform in public.  Otherwise my picking technique’s flaws show up — and more importantly, I’d be self-conscious of my picking and will be timid in my playing.

Buying an affordable Boss pedal and modding it seemed a very cost-effective thing to do.  The mod kit had clear directions and I was successful in modding it in one night.

Well, this isn’t a review of the mod itself — but the resulting pedal, how it behaves.  I realize that sonic reviews of mods are hard to come by, I hope my descriptions will help you determine if this pedal/mod is for you or not.


You get your Volume, Tone, Attack and Sustain knobs.  Attack knob adjust the attack time — the counter-clockwise will kick the compressor in earlier, squashing more of your pick attack and making the note seem more even in volume but quieter compared to having a longer attack time.  But even when the attack time is set to maximum length, it’s not long enough to entirely leave you attack unaffected.  The Tone control affects the treble but its frequency range seems fairly broad — turning it up doesn’t make the pedal ice-picky or anything, just louder and brighter.

The kit includes a super-bright white LED, which really stands out and makes it clear when the pedal is on, which is a nice touch compared to the stock, dull red LED.


The stock CS-3 is somewhat muffled and anemic sounding, but with Opto Mod it really becomes more alive and refined.  Of course it doesn’t do the blending that many modern guitar compressors do, so even when used subtly it still affects your pick attack, and thus the playing feel.  If your goal of compressing is to simply add sustain and not change the feel/attack, then you need to look elsewhere.

It’s nice that the pedal doesn’t seem to accentuate the highs or lows — it is fairly neutral sounding, which makes it versatile.  Some compressor put more of a sonic signature on the tone, with either boosted highs that sparkle when used clean but adds annoying highs when used with dirt pedals, or muted highs that results in reduced note definition.

My Verdict

The Opto Mod makes the humble CS-3 come alive with more hi-fi tone.  It does squash your attack but in a different way than, say, what you hear in stereotypical country-style compression.  Less snap and more bell-like.  I think its main applications are:

  1. Have a more neutral yet hi-fi sounding clean compressed tone, or
  2. Use it as compressed boost into your dirt pedals.

If you’re looking for more Ross/Dynacomp-style squash (though it has fair amount of squash) or simply looking to add sustain without affecting the attack/feel, then this isn’t the pedal for you.

I’m not exactly a compression connoisseur but I have tried likes of Demeter, Maxon, Menatone and MXR compressors.  They all are different and suited for different purposes, but I’d say CS-3 with Monte Allums Opto Mod can hold its own against these more higher-priced competitors, especially if compressed tone with somewhat neutral frequency response is important to you.  Its strength isn’t in transparency or classic squashing, so do consider what it is that you’re looking for in a compressor and then start looking for a pedal that meets your goal.

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