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REVIEW: Monte Allums Boss CS-3 Mod



This is a review for the Monte Allums CS-3 Opto Mod Plus.
cs3modMany claim the Boss CS-3 is a great sounding compressor just as stock. Well, I admit is is not bad…but great? I must respectfully disagree. But then again, I’m no Stevie Ray either so perhaps more talent than I possess is required to make this baby sing. Being that as it may, I just was not impressed with the CS-3 out of the box.

It was my experience with the Monte Allums SD-1 mod that led me to pimp the pedal. After receiving my brand new CS-3 in the mail and using it for a few weeks, I went ahead and put the pedal under the knife once my kit from Monte arrived.

Instantly, I saw why this mod was so highly recommended. The crispness of the compression just floored me, and the sustain was like riding a perfect wave ( putting knob at 12 noon sounded just perfect for me ). A very, very natural sound comes from it now.

The mod even goes so far as to replace the stock on board amp with RC4558P and Burr Brown OPA2134PA Chips. This is done to fix the infamous noise problem, and I can tell you from experience that this does indeed do the trick. You get a clean overdrive signal, and nothing else. Well, unless you pump it into an overdrive and crank it up…but that’s to be expected because now you’re technically simulating distortion.

After this mod, I rarely if ever turned my new CS-3 off just because it made such a fantastic sound. Combine this with a modified SD-1 Overdrive, and you may well have all the pedals you’ll need for most of your jamming. Considering the sorry state of the stock CS-3, BOSS should hire Monte as a technical consultant!

One of my guitar instructors, who is not a Boss fan by any means, was floored when I brought this into my lessons. He didn’t think such a thing was possible for this pedal, even though he had heard about the mod.

The Opto Mod Plus in my opinion, can get no less than a 5 feathers out of 5, for taking something rather vanilla and making it sound so freaking fantastic.

5 Feathers out of 5.


John Paul Parrot ( aka. The Dysfunctional Parrot ) is a disgruntled Systems Analyst who wanders the Canadian wastelands saving small villages with the power of Kung Fu.  His chair is also a little too close to the twenty year old microwave.  As you can well imagine, this has had certain side effects.



  1. Daniel

    August 26, 2022 at

    Thank you for the review, it was veru helpfut to make a decision

  2. dfx

    August 18, 2011 at

    Thank you for the reply.

    Likewise i am also a hobby guitarist(room only)/neighborhood guitar tech/church sound tech/etc.

    I will let you know also any further observations as i will try it for vocals and other instruments as well to check how it performs well.

    Primarily i have been using it only for guitar along with my other pedals.

    I have Line6 PocketPod also and their products I should day are great, really great.

    • Dysfunctional Parrot

      August 18, 2011 at

      Please do! I'm always looking to know what's good out there. I too am very impressed with Line 6. Yeah, I know many look at me like I've committed treason by using "simulators". But after 10 minutes of using the TonePort I packed up all my pedals! How else can I go from a U2 to Boston to a Lincoln Brewster setup that sounds amazing all in just milliseconds? Gotta love it!

  3. dfx

    August 17, 2011 at

    I had the first MA Opto mod plus utilizing only a single OPA2134 chip replacement around 3-4 years ago. Last night i toyed with it by trying different ICs,i.e., MC1458, JRC4558D, and LF353 against the OPA2134.

    MC1458 giving the obvious high noise floor against all the other 3. The settings on the pedal are all at 12 o'clock. I was monitoring thru a headphone out from a small Fender Dice Amp. The other 3 are hardly distinguishable from each other in terms of noise floor. With regards to level and headroom, the LF353 and OPA2134 beats slightly the JRC4558D.

    In these regard, i would like to know if you tried swapping ICs and have taken observations as well.

    • Dysfunctional Parrot

      August 18, 2011 at

      No, I never got that fancy! In fact, I had to re-read your comment several times to get the gist of what you were saying. :)

      In the end I sold my compressor and got a Line 6 Toneport because I'm just a hobby guitarist and am still a long way away before I'd feel comfortable on stage. Maybe when I need a stage setup I'll look at reacquiring another CS3 which I will absolutely do the Monte Allums mod to again!

  4. Dysfunctional Parrot

    April 12, 2010 at

    I've done the Keeley "all-seeing-eye" DS-1 mod, but I was a bit of a guitar noob at the time. I eventually sold the pedal because in my opinion, it was just too much "crunch" for my style of playing. I ordered a Monte Allums SD-1 mod and that was more in line with what I was looking for.

    Since all this, I have sold all my pedals and got a Line 6 Toneport. Yeah, I know…the age old battle between pedals and multi-effects units…but there is no end to the sounds I can get out of this thing!

  5. blastedmutants

    April 12, 2010 at

    I hear you. The stock cs-3 is all hype. Have you tried any of Robert Keeley's mods?

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