Modifying an Alesis 3630

[audiovisceral]

Like many I have an Alesis 3630. For fun, because it is rare to find a dual compressor with such flexible controls for such a great price, and since I've heard numerous reviews about how nice it sounds following upgrades, I am thinking about doing some mods on it.

For my benefit and others, I have collected the different mods suggested across this board and from other sites. I hope to get some feedback on some of the questions I have posted, and I hope this will be useful for anyone else considering a mod on one of these units.

The mods are as follows.


PSU:
•) Replace the adaptor with a 1.5 watt, 2000ma, 9vac Line6 PX2 adaptor (http://accessories.musiciansfriend.com/product/Line-6-PX2-Power-Supply?sku=150387).
•) Replace the four diodes near the power jack with 1N4004 diodes to ensure they are working correctly.

OPAMPS:
•) Replace the 3 LF347N quad opamps with an upgrade like LME49740 or MC33079P - use 14 pin sockets.

VCAs:
•) Replace U3 and U7 (DBX2150) with THAT2180LA - use 8 pin single row sockets.

CAPACITORS:
•) Replace C2 and C3 with 220uf/35v electrolytic capacitors.
•) Replace C4 and C5 with 2200uf/25v electrolytic capacitors (they need to be short because space is tight here).
•) Exchange C8 and C26 for higher quality capacitors of the same value. These were left out of some of the early 3630 models in which case they should be installed. Rev D (and I think Rev C) already has these included already so you can just replace them.

GATE:
•) Replace gate threshold pot with '10k audio taper pot with a SPDT switch'. The SPDT switch should be wired across the jumper cut in the TapeOp "Two-Snip mod" so the gate will be removed from the compressor circuit when this pot is turned off.

BALANCING I/O:
•) Add a balancing/unbalancing card like audiox (http://www.groupdiy.com/index.php?topic=29333.0). The audiox should still fit in the existing chassis at the opposite end of the AC adaptor, but new offboard chassis mount I/O TRS jacks will be needed.


QUESTIONS:

My first question is regarding the implementation of a balancing/unbalancing input/output card. With the new 2 amp Line 6 adaptor, I think (hope) there should be more than enough current. I understand the 3630 uses the 9V adaptor to generate 15V +/- for the compressor. Where would I have to install leads from on the board to tap some of this 15V +/- to the balancing board? Would it be possible or safe to do so?

Next, regarding the switchable gate, the writer here (http://messageboard.tapeop.com/viewtopic.php?t=27676&sid=bc33cb1d20f2cdca4e8fc857a6c088c7) says there is a way to add an SPDT switch to the existing gate threshold pot so it does not have to be removed. Does anyone know if this can actually be done or what the parts are to do it? Otherwise, does anyone have a part suggestion for a 10K audio SPDT pot that might fit the board?

Also regarding the gate, does anyone have a reference or picture of the TapeOp "Two-Snip mod" that tells which jumpers you cut to disable the gate (where to install the SPDT across)?

Regarding the VCA mods, I have a note in one of my messages that says: "With the VCA socket, remove the pin for pin 4. Make SURE that you orient this the right way-- pin 4 on the VCA should not be connected." I am not sure what this means or if it is actually required though, since the recording.org article (http://web.archive.org/web/20030121190000/http://www.recording.org/e-mag/article_81.shtml) doesn't mention anything about this regarding the VCA upgrades.

About the capacitors, I notice mine features many small orange ones (eg. C12, C13) in place of the blue ones in the photo attached. They look like ceramics (http://www.clickpartelectronics.com/images/TS15_Ceramic_Capacitor.gif). Would it not then be better to replace them, for example, with something like WIMA polypropylene?

Lastly, does anyone have a schematic or service manual of the Alesis 3630, ideally Rev D? Since the 3630 patent should be expired and this is for educational, non-commercial use, I think it would qualify perfectly as fair use to post.

Thanks.


CREDITS:
Mod suggestions from: jrfred453, rascalseven, mrc, recording.org via archive.org (http://web.archive.org/web/20030121190000/http://www.recording.org/e-mag/article_81.shtml), MintFieldMan (http://messageboard.tapeop.com/viewtopic.php?t=27676&sid=bc33cb1d20f2cdca4e8fc857a6c088c7). Photo attached from jrfred453 - note that you don't have to off-mount the adaptor plug as shown.

 

[canidoit]

What improvements does this mod do to the Alesis?

How would the modded alesis compare to other high end compressors?

 

[audiovisceral]

What improvements does this mod do to the Alesis?

How would the modded alesis compare to other high end compressors?

From the guy who originally posted many of the suggestions: "A cool mod for those interested. This really does turn the 3630 into a really surprisingly useful unit. Haven't heard mine sound bad yet, even on fast attack/release and steep ratios !"

In the words of Recording.org, referring to just the upgrades on the VCA: "I'm not saying that if you follow these steps that you'll have an 1176 or an LA3-A, but the quality of sound exiting the box will be vastly improved merely by swapping out a few components."

The idea is to just correct for some of the corners cut by Alesis in mass manufacturing. It brings the main audible components up to a 'high end' standard. I expect it should be somewhat comparable to any other transformerless VCA/IC compressor - eg. Distressor (minus the emulation modes), dBx, GSSL, Pico, or any other. A 3630, but cleaner, clearer, and more responsive.

Anyone I've seen or talked to who has done this stuff has been quite satisfied with the result, for whatever that is worth.

 

[mitsos]

Never done this or even seen the inside of one of these, so confirm this first...

As far as the +/-15V, it looks like you might be able to take it directly from the outputs of the regulators...

The pot/switch.. Omeg makes some and they'll likely send you a couple of samples if you ask nicely.  Just measure the width of the original pot bodies, and the lead spacing. looks like you have enough room behind the pot for the switch. No idea about the actual mod.

VCA pin 4, looks like it's for the pre-trimmed 2180 series. You should not *HAVE* to cut the pin. Maybe just bend it. Check the GSSL help thread for details on this.

Not sure which caps you are talking about, but the larger blue one in the photo look like some kind of dipped film. Maybe check what they are doing, and replace with either better ceramics (C0G/NPO) or polys that fit. Polypropylene are fairly large depending on value so check the datasheet first to make sure that they'll fit.

There was a schematic around here some time ago. Try a search and maybe email/PM someone who might have had it. Maybe they still do.

HTH!

 

[audiovisceral]

Thanks Mitsos. Yeah I guess I can just solder my 15 +/- wires to the 7915/7815 legs. I can just use a multimeter with the unit on to see which legs are giving what, right? I think the legs I would want should be the ones closest to the pots on both.

Regarding the jumpers to cut to disable the gate, I found the old thread showing it and attached the pic:

http://www.groupdiy.com/index.php?topic=210.0

Does anyone know if the two jumpers shown are separate for each channel or if they both need to be cut simultaneously? I will probably just use a single DPST/DPDT to save time, but if they could be cut separately, I could also use two SPST/SPDT switches instead (one per channel).

Either way, it looks like either of this style Omeg pot switches will fit perfectly, so thanks for that as well:

http://www.omeg.co.uk/pc41ow2r.htm
http://www.omeg.co.uk/pc41ow6r.htm

Regarding the capacitors, I'm pretty sure the little orange ones on mine are ceramics. In most places there is plenty of room for some WIMAs. It might be a pain in the ass to desolder them. But they've got the values printed on them so that should be doable.

That jumper thread also mentioned another mod from smallbutfine I'm curious about:

"Very easy as well, I soldered a bridge from the tip of a sidechain insert to the tip of the corresponding out (this was a very cool idea, whoever came to this first... )."

Can anyone explain this to me in more depth? It's a bit over my head what this is means and how to do it.

Thanks again, guys. I'm sure it seems a bit crazy the idea of putting this much effort into a 3630, but at least I won't be the first.  

 

[SIXTYNINER]

hey,
cool "customization" ..!

but why spend time and and money for a 100$ compressor....
why not buy a used d - b - x

 

[audiovisceral]

hey,
cool "customization" ..!

but why spend time and and money for a 100$ compressor....
why not buy a used d - b - x

A couple of reasons. I actually kind of like the 3630 in a weird way. It has controls for every parameter a compressor needs. I am also a fan of Daft Punk (who used it to great effect on their older stuff) and Billy Corgan (who used it a lot on Mellon Collie). So I feel like maybe there is a good compressor in there that wants to come out.

I just basically need the 2 THAT chips, one balancing board, and 4 trs jacks. I decided I will install the jumper switch as a simple dpdt on the back of the chassis, so I won't need the special Omeg pot. $20 adapter. Caps are cheap. Seems simple enough.

If I bought a budget dbx like a 166xl/266xl I'd feel compelled to mod that too, so no difference there. Maybe it would be better? I don't know. My biggest complaint with dbx units are the relatively slow attack times. Although dbx uses similar chips, the compressors don't behave the same way.

We'll see.  

 

[Rob Flinn]

A few years ago a friend asked me to mod 1 of his 2 alesis 3630, so we could compare the unmodded to modded one.  I don't remember exactly which of the known mods we did, but we did do quite a few.  

I do remember that neither of us noticed any significant difference.   This may be contrary to other peoples experiences, but I guess I'm entitled to my opinion as much as the next person !  If you fancy trying it out, I say go for it, it won't cost you much money.

 

[abechap024]

Hey
Cool about modding the alesis....
I haven't looked at the schematic but modded an old at66 audio logic POS compressor (based around the 2150) and all the same general controls. My old band mate bought one of the alesis and remember kind of using it....

Anyway. I would recommend changing the timing capacitors to Taltanum. Tants have a very quick and consistant discharge rate and you'll find all the "classic" compressors use them.
If the alesis already uses them sorry for the verbal garbage, but they probably have some cheap electros that will make the compression sound...welll cheap!
HA
good luck interested to hear your results!
AC

 

[thomasdf]

A friend of mine gave me a 3630... I tried it yesterday and was quite dissapointed with it...
It is dull and doesn't have any punch to it... Everything you put thru it just sound like a chocolate bar left on the back of a car on a parking lot during summer... It just completely melts in an uncool way.

Are your mods giving it back some thightness? I really don't want clean compression but I'd like some cool behaviour to squash room are snare. The gate could be a cool feature but here again it just has no snap at all...

 

[karg]

Hi guys,

although this is a rather old thread, I found it when I was specifically looking for ways to upgrade my Alesis 3630.

By now, I have applied the mod and added some other replacements found on various homepages. I am far from being a professional, but I must say I also do like the compressors sound now and the mod was fun to implement.

In case anyone is interest in modding their Alesis as well, I return the favour and have posted detailed instructions for my replacements on my blog:
http://karg-music.blogspot.de/2015/10/alesis-3630-compressor-mod.html

, Karg

 

[bernbrue]

A friend of mine gave me a 3630... I tried it yesterday and was quite dissapointed with it...
It is dull and doesn't have any punch to it... Everything you put thru it just sound like a chocolate bar left on the back of a car on a parking lot during summer... It just completely melts in an uncool way.

Are your mods giving it back some thightness? I really don't want clean compression but I'd like some cool behaviour to squash room are snare. The gate could be a cool feature but here again it just has no snap at all...

Hi,
I´ve bought this compressor for almost nothing and  came across this thread.  I did some measurements and I can only say that this vca compressor makes a good job. The specs are not that bad and soundwise I can´t complain either. I´ve attached a pdf file with RMAA measurements.
Bernd

 

[JohnRoberts]

the 3630 is an inexpensive platform with all the components to make a compressor.

As often happens details matter. I have shared this before but in dynamics processors  the linearity of the gain element (VCA) matters only in the margin, and generally does not dominate the audible character. Better is always better, but don't expect a night and day change. From swapping VCA and op amps.

Having all the sundry parameters variable is good, but there can be subtle differences between 3630 fast/slow and another compressor's fast/slow.

By all means they are inexpensive and good DIY projects to mess around with, just don't expect to magically end up with a premium processor, while it can be made better than stock (at least on paper/test bench) just from upgrading to modern VCA.

JR

 

[smilan]

Hi,
I'm thinking about modding my 3036, does anyone have sound clips of before / after the mods?

 

[Script]

Visited one of the many audio thrift stores over here the other day, as I often do, looking for cases to reuse and came across the infamous Alesis 3630. Last time I had hands on one was last century and it hadn't impress me at all. There was something about that unit that stuck -- in a bad way.

As a case for reuse it's too small for almost anything -- almost But it was so ridiculously cheap and the store even gave a 3-month guarantee on it, so I couldn't resist and was also sure it would fully 'work', giving me the chance to revisit that 'awful' sound one last time before slaughtering that thing. So I did a very brief listening test and turns out it didn't sound all that bad as I remembered it. Maybe usable for something after all ?? Tracking ? Maybe... Nah, probably not.

But, hey, it also has a switch potentiometer on the gate -- not so common and good to have around maybe for a quick repair or some build maybe... but weird, I thought, it must be a later version that probably implements many of the circulating mods developed by Alesis beta testers (=Alesis customers) -- some mods that apparently had made it into later official production revs. So it must be a later version. But bah, whatever, I want the case... so I put the thing aside.

Today I opened it and... surprise !! Turns out it is a substantially user-modded rev D. Alongside the switch potentiometer, the entire power supply has been modded, most caps don't look factory original, even in value I think, there are a few metal film resistors, but not everywhere, the selector switches on the back had been replaced for rugged ones, the gounding of the jacks somewhat strengthened (?)and there are SMD LT quad op amps, one of which alone costs more new than I have paid for that entire unit. -- A late X-mas thingamajig, interesting.

So I did some research in the catacombs of this forum and elsewhere, and what I think is that somebody had probably given it some thought, beefed up the power rail and the audio thru path, addressed (some of?) the noise, but apparently didn't touch so much the sidechain, as they kept the LF437 ---and I think I know why [the sidechain is the compressor sound] but I would need to look much closer though -- they kept the LF probably to retain the unit's sidechain 'signature sound' (some call it oumph, others call it mud) used on French house etc, but at an overall more acceptable audio quality (S/N, THD) ?!? Maybe a partial Black Lion mod or at least inspired by it ? Or maybe not.

Anyway, to cut it short, it might get spared the slaughter, for now. It calls for some measuring and testing, and if promising for tracking also probably needs a few new caps --they only gave me a three-month guarantee after all -- and possibly a closer look at the knee in soft mode, which I think still sounds strange on this one. But : take ticket please, end of line.

Anyway, just thought I'd share this, as this piece of craftsmanship is among the oldest discussed on this forum. Maybe interesting to some. And who knows, a couple more years and the French House era sound might be en vogue again.

 

[RuudNL]

Years ago I modded one on request. (Based on a 'recipe' on the internet).
I had to find expensive hard to find Burr-Brown OpAmps, mica capacitors etc.
The result: no noticeable difference! A waste of time and money!
The only thing that was an improvement, was additional cooling of the voltage regulators, because they ran very hot...

 

[Script]

Micas, yes, I think this one is full of them, the blue ones (CY22 ?). Expensive and together with 50Mhz quad op amps bordering on a money burn (and possibly hi-freq oscillation) fest.

This thing is all thru-hole and very easy to disassemble for tinkering with it (unlike any old Behringer gear which is a pain to disassemble and even worse to reassemble).

Yes, it's a 'functioning toy' after all or usable as a platform, as JR said above, with the case, pots plus two detectors and the two VCAs all coming at the cost of a burger meal.

Anyway, if I had chosen this unit for modding, I'd have started with the too sparse design of the sidechain. Not VCA upgrade though, never did on any old Behringer either. Might still do -- there is a bit of headspace in the case -- or just rip it apart.

 

[Script]

Had some time to spare between metal work, wiring and having waited long for stuff to arrive for several other units. So briefly looked at Alesis schematics and did some quick tracing (audio path and around RMS & VCA).

- IN is unbalanced
- BYP is not a hard bypass (deceptive when comparing)
- 2252 RMS detector is straight out of the datasheet and even properly linearized, it seems but,
- Soft/hard knee is not DC compensated (bias)
- while VCA misses control port buffer (!!) and also misses cap to ground (filtering) before signal hits EC port
- and OUT is not only unbalanced, it comes straight from the VCA output buffer (hush hush, damn it)
- also I don't really like the voltage doubler PSU much.

And I'm sure there are more dodgy aspects. -- Well, turns out this isn't even a veggie burger.. but quite some jalapeno sauce added to it =8/

 

[analogguru]

Pssssst:

If you would buy a used Behringer MDX1000 you would get an Alesis 3630-CLONE (without the noise gate) but with additional balanced in/outs and a proper built in power-supply. If you don't need to have a CLONE you can also go for a used MDX1200 or MDX1400 which are (slightly modded) Alesis 3630 DERIVATES.

(Another Behringer clone which is better than the original..... just saying.... )

 

[Script]

Thanks. Yes, I am aware, read your posts about the 1000.

I used one of the follow-up units some 10 years ago as a platform for study purposes and throwing all sorts of circuitry at it. Wouldn't do that with the Alesis, after what I've seen.