Wednesday, February 11, 2015

Alesis 3630 modification. Is it good? Or the worst ever?

I picked up an Alesis 3630 for $24 on eBay.  I have heard so much about them I had to get to the bottom of it myself.  Also, Billy Corgan used it in his guitar rig on the huge sounding Mellon Collie and the Infinite Sadness, and Daft Punk as a master compressor on their huge sounding albums Homework and Discovery.  So there could be something to it...

The first "mod" is to get a 2 Amp power supply (wall wart) I hear that the original ones are quite wimpy.  This part was about $18.

The second mod is to replace the caps in the power section.  This is where I ran into trouble.  I used 2,200 uF caps in all four position, but then one of them exploded.  I replaced it and it exploded a second time!  This was terrifying and disheartening.  I have heard of this phenomenon but this is my first time encountering it.  I believe that 2,200 uF was far to big a value for C2 and C3, and they were probably drawing too much power.  So I replaced them with 220 uF caps (C2, C3) and C4 and C5 I returned back to their original 1000 uF value.  I was too nervous to try 2,200 uF in there again.

So I cleaned up the mess, replaced a ceramic cap that got shattered (!!) in the first explosion, and let it run for an hour and a half.  This was nerve wracking, I kept expecting more popping caps.  After about two hours I felt OK to put it back together and start passing audio.

Let me mention the first nightmare.  When I pulled the knobs off for the initial disassembly, about 5 or 6 pot shafts got ripped out along with the knobs... nasty.  I don't know if some hapless punter glued them on or what.  So ordering replacement pots, and doing that part of the job, added a lot of extra time and work to this apparently ridiculous project.

The audio quad op amps that came stock were a respectable TL084CN (earlier revisions had much worse).  But I had to see what all the upgrade fuss was about so I installed sockets and a pair of Burr Brown OPA4227PA.  The two of them cost me about $5 on eBay.  So now my total investment in this 3630, including pots, is around $50.  Not bad.

I also replaced C16 and I think C33? (the other side of the board) with Panasonic electrolytic caps, since they are in the audio path.

Removing those caps gave me a little room for the nasty part, which was ripping apart the quad op amps with angled cutters.  Once you get one half of the op amp's legs snipped, you can just wiggle it back and forth a bit and then the other half of the legs will break eventually.  After this, pull the legs out with a soldering iron and some tweezers or grabber of some sort.  Then you can clean up the holes with desoldering braid (and a very hot soldering iron).  Once the holes are nice and open, you can put in a socket.  Then you can put in your new C16/C33.  After all this brute nastiness, now it's time to gently slide in the Burr Brown op amps... ahh....

Another word of caution.  I think the ribbon cable leading to the LED meters could be kind of delicate so be careful.  My left side gain reduction meter doesn't work any more.  I don't know why, but maybe I was rough on the ribbon.

The 1/4" jacks also needed a heavy dose of contact cleaner, and I refreshed the solder points for good measure.  I was getting some audio glitches from here but not after the cleaning.

I don't know which was more disgusting to work on, the Alesis 3630, or the Behringer MDX2100 Composer.  Both pretty revolting.  But in the end, they are both nice compressors to have working in the rack.

How does it sound?  Dirty-six-dirty is about right.  You get this kind of cassette tape, gritty, slightly dark on top, sort of big on the bottom thing.  Think Daft Punk, or Mellon Collie guitars.  Things sound a bit bulbous and sort of cartoon-like, a little low-fi or fuzz around the edges.  Which can be a useful sound, to my ears.  The Composer is a lot crisper and cleaner.  Honestly it wasn't that bad pre-mod either.  By the way--If you own an earlier '90s pre-Rev D. model, you might have to add a couple caps in the detector circuit, you can google this mod.  Mine already had them.  You can also snip some jumpers to take the gate out of the circuit and clean up the sound, but I didn't do this, I guess I wanted it 'kind of stock'.  And if you've got an early one with a comparator IC as one of the quads, that should be replaced with an op amp as well.

This sounds nothing like a DBX.  The compressor's action is not so defined or obvious, or quick I guess.  The attack and release, ratio controls are also not as responsive as I'm used to hearing in other compressors.  You can really smash the gain reduction meters, it seems a lot of people use 3630 like this.

It's too early to tell how much I'll use this, but it has a flattering sound that can work great for fattening up a thin sounding fuzz bass, for example.  I'm sure it would work great in a live-instrument rack, too.

Worst compressor of all time?  I doubt it.  Not bad.  I can't tell you how good it feels to be done with this one though.  I do plan to use it and it's been sounding cool so far!  The power supply lesson learned the hard way was probably worth the project alone.


  1. If you were going for the Daft Punk style pump and compression would you disable the gate? Or do its artifacts add a kind of character?

    1. I found the gate cut mod to be very subtle. I almost couldn't really hear it. I would probably make that decision based on whether or not I needed or wanted to ever use the gate function. I don't, so I felt comfortable cutting the gates.

      I think even after all these mods, that "sound" is still there that you are looking for, the sort of tight squashed thing. It just sounds cleaner and a bit more transparent, but the compressor action is the same.

      The big thing for me was selecting the op amps in the audio path. The Burr Brown OPA4227 gave a nice sort of warmed up kind of sound, a little smooth and a little colored. The MC33079P is brighter in sound but overall it's extremely transparent, which I find slightly more versatile using the 3630 as a master compressor. It has less of a sonic footprint, so it doesn't affect your mix EQ too much. The Burr Brown was a nice sound though, I would probably use those if I was going for a channel or instrument compressor for individual tracks, due to the slight extra character. More of a "vintage" sound profile.