3630 mod meta

[rascalseven]

I have a couple of 3630's modded with Butta's mod at my studio.  I still get the occasional odd look from visiting engineers -- you know, that "you've got TWO Alesis 3630's in your rack?" look (which seem out of place alongside Neve 1084's and 1090's, API 312's, Drawmer, Vintage Design, etc.), and they're always shocked by how good they are when they finally get around to pluggin in to them.

I considered the Black Lion mod (bought the info from him, in fact), but most of the 'mod' was just replacing carbon comp resistors with 1% metal film and replacing ceramic caps with mica.  There was very little actual circuit mod as I recall (and I did try the IC's he recommends, but they just had a stark, hard character to them... didn't feel as musical as TL074's or MC33079's that I tried as well).  I went with the 33079's.

So in a nutshell I modified the power supply per Butta's direction, swapped the quad IC's to 33079's, and I changed the timing cap for the 'peak' function to 1/10th the original value (for faster response time capability).  My units had rev.D boards, so the 1uF timing cap was already on the 2252 (necessary!).

I didn't replace the 2150 VCA's.

I love to use them in peak mode.  They're wonderful now, even (especially?) under heavy reduction -- like -20dB.  My one gripe is that they can't push much level before crapping out (audible 'snap' on transients at higher output levels), so I generally have to print a little low on the output to keep it sounding nice.  I keep thinking I'll get around to adding a simple balancing stage on the output to increase my overall output level, but just haven't got around to it yet. 

JC

 

[smallbutfine]

Once in a while people come back to the 3630 on this board - and yes, this is absolutely necessary!
In fact I think the buttachunk mods that I did were probably the most rewarding piece of diy I ever did besides modding 2 old vitalizers.
Extremely high usability value at a very low price level.
The most complicated thing was actually the disassembly. I even cut away a part of the upper pcb to get one of the big psu caps into the box, hehe. Low parts count mod, very good availability, one evening and a very huge effect.
I even put 3 of the pricier burr brown into them (opa 4227). Even if they alone cost as much as the whole unit new, I would never look back. It sounds beautiful to my ears.
I also had the Rev. D board, and it even already had the 2180 VCA stock!

I guess the blacklion mod used fast video opamps or so...don't know if all those massive parts changes included in that mod actually pay off really, compared to buttachunks. I never felt there was a need to do any more on it. It really sounds totally right.

JC, did I understand it right? Did you change the 1uF of the Rev. D board to a 100nF? Did you use a film, mica or tantal?
I nearly use mine exclusively in rms mode until now....

Kind regards,
Martin

 

[jmejia]

Where is butta's mod? I feel blind as I'm reading butta's meta and unable to find a link to the details of his mod. . .

 

[okgb]

Butta [ and his links ? ] left the forum some time ago
as the result of some version of everyone not getting along
careful what you criticise

Otherwise there should be allot of general upgrade links
to the 3630 , no ? try google

 

[smallbutfine]

@jmeja:
From memory, I made that mod directly after butta posted it, like 1:1, so here is what I did, posted once again for new members.
Since there is so little parts count to change, use good quality parts really. It will pay off.

1. buy a better/huge >=1.2 A external wallwart powersupply!!! ESSENTIAL

2. disassemble the case

3. change the both/all huge capacitors on the lower pcb(located left if you look from the back) against minimum(!) 2 values higher capacity, high quality, low-esr types (e.g. Panasonic FC, Nichicon (Butta used these if i remember right), Sanyo Os-Con (I used these) or similar). Choose packages that fit the case! (I had to cut parts of the upper pcb to get mine in....grrrr). Take care of correct polarization when soldering in. ESSENTIAL

4. Remove the three quad opamps in the middle of the lower pcb. clip the legs and then desolder. Remind the chips orientation!!! the stock ones are cheapies not worth keeping. Solder IC sockets in place. Now stuck better quality opamps in, like MC33079 (cheap, 'surgical clean' sound, I think butta used them), TL074 or TL084 (cheap but darker, grittier), OPA4227 (more expensive, smooth and musical, I used them and was very pleased), OPA404 (expensive, very clean and quiet!) or similar. Try out different ones, the circuit changes sound alot with different kinds of quad audio opamps compared to many other circuits. Chances are good that you can get the sound character you were looking for as a matter of personal 'taste'. The middle quad opamp is for sidechain and can be chosen differently, the other both *must* be of same type (stereo tracking/signal chain).
If the middle sidechain quad is LM324 or similar, exchange is ESSENTIAL. Dont underestimate this one, quality pays off here.

5. if the board is below revision D you have to add 1uF timing cap to the 2252 chip (look at THAT Corp. application note for the 2252), ESSENTIAL

6. if your 3630 is stuffed with 2150 vca, you *might* consider replacing with 2180 vca (not essential but lowers noise and distortion a bit)

7. strap a piece of copper across all jacks ground to help more proper grounding. (helps, is easily done and costs nothing but is not that essential)

8. you may bridge the cheap output level selection switches if you don't need them (decide on the fixed level you need). they are cheap and may add unnecessary resistance/noise at the contacts. (well i did not....but it costs nothing and prevents unnecessary problems)

9. if the 4 psu diodes on the left/back of the lower pcb are not 1N400x types, replace with 1N4003 or higher, better even UF4003 or higher (faster and still cheap). beware of correct orientation, like with the caps.

10. re-assemble the box
Fire up! Night and day transformation.

The trick with this mod is, that it just fixes the essential flaws that make the biggest difference in usability and sound to the better, i.e. the seriously underdimensioned PSU, the missing timing cap in pre-Rev.D pcb's and the comparator that is misused as an audio quad opamp in the sidechain. These fixes make it a usable box alone, while all together makes it a seriously good sounding versatile studio tool for pro-audio use. Read: As good as any major quality brand compressor based on that vca, maybe even better.
All at a really low cost still and an evening of concentrated soldering.

It's years ago, but I still remember how extremely rewarding it was, after it was done i spent the whole night feeding sums thru the box and couldn't get enough of all the cool settings that were possible. I just couldn't believe it. I still use it very often. A secret weapon maybe worth 3 times the money or more it cost me including all parts and work. I never thought of tweaking it further, like other mods do, because I can not imagine that it would make such a great effect compared to the additional work and cost. Completely happy with what it is now. (in fact i use it more often than the in my opinion great sounding EMT266 limiter that i used on nearly everything before)

Kind regards,
Martin

 

[tchgtr]

Very nice. Thank you for taking the time to do this.
I bought one of these today for this very purpose.

 

[smallbutfine]

Ha, you're welcome!
So, happy easter holiday and take your time, not only on the 3630 but also on family

 

[tchgtr]

Thanks Martin, and same to you...Looks like I got a Rev D (35 USD used!), so I'm just looking at power supply, grounding, and audio caps right now. Might buy some nicer chips later, but think I'll stay with the TLO84 for now, though the middle chip is a LF374N.
I have a 13.8VAC 1250 mA wall wart that I use as a spare for my GR-33. Will this be OK with the 3630?
This July, I will be in Belgium and the Netherlands to teach. Maybe I will get a chance to buy you a beer
All the best,
Jim

 

[smallbutfine]

Hi tchgtr,
13.8 are much too much for my taste, the 3630 needs 9VAC, 12 may be ok still, but ~14? No, the regulators may run just too hot in the small box...
Btw, i got a cheap wallwart off the fleamarket, 9V / 1.2A and it worked flawlessly since. Cost: 1 buck! Try the second hand electronics guy (you know, they mostly sell cell phones but somewhere they have a box full of wallwarts on the floor......) and invest a few bucks.

SECOND: The LF374N was exactly the chip that I was talking about to be ESSENTIALLY replaced.(I was wrong with LM324....)
Do yourself a favour, get some IC sockets and replace at least this one with any kind of quad opamp you have (TL074/TL084/MC33079 whatever comes in your way - every electronic parts store might have one of those and it is cheap cheap cheap.
This LF347N actually ruins compression behaviour and also leads to noise in the audio signal chains. PLEASE do not close the box without at least change this one. You will regret it for sure. The TL084 in the audio signal chains are ok to leave as they are....
You might not know this, but replacing the comparator with an audio-related quad opamp was probably the first mod ever made to 3630, because it is such a bad flaw in this design..
(I guess peter purpose told us first about this many years ago, when he changed opamps and wallwart and cut the gate in the first attempts to improve this thing....)
With the Rev.D board you might be lucky and probably you can get away with buying just FIVE CHEAP PARTS (wallwart, 3 caps and a replacement quad opamp for this particular inacceptable non-audio chip that degrades the compression side chain.......) so I think you may even get away with UNDER 50 bucks for the whole thing - you cannot go any cheaper without serious sound quality loss.

Best regards,
Martin

Ha, I do not know what I am doing in july yet (by any means), but thanks for the beer, I even drink the virtual ones.... ;D

 

[tchgtr]

Understood.
  I have been listening after PSU changes --- 2200uf upside of regs, 100uf downside with protection diodes.
  With old wallwart (9v, 740mA), lots of distortion. Tried the 13.8v (!), and it sounded better, but still some weird, modulated, mid-range distortion that increased with higher output levels. Yes, the regs got a bit warm..but no smoke after a half hour or so.
    Cut the jumpers, and experienced the same thing as mentioned in another post --- the gates are still working, but much higher output levels. Distortion still there with output at about 0. Can hit a sweet spot every so often that sounds pretty nice. Compression seems more transparent, and highs and lows sound good---just that muck in the mids, and some noise (kinda motorboat-y).
  I'm pretty well-read on these threads, but with my inexperience, I had convinced myself that the side chain wasn't going to affect the sound if I wasn't using it. Now I see the error of my ways, and will take your excellent advice.
  My local surplus store only has LM324 and MC3401 (equiv. 3900), so I might check the pin-outs and try some 8-pin stuff. I have lots of Burr Brown and J-fet 8-pin stuff on hand.
    Fortunately, I have good solder skills after 2 years of DIY mania, and this will be simple. I will look for a safer wallwart too.
  BTW, I also have an ART CS2 that looks suspiciously like the 3630. This will have to be dismantled soon to see if similar changes can be made...
  Please accept another virtual beer. You will be virtually smashed by the time I get this right...

 

[smallbutfine]

While you are already at it:
Re-solder the gates back in. When butta's mod is done correctly, they are completely usable! Also, when the gates are cut, controls and indicators are not showing correct values anymore.
'sidechain' in this case also means the *internal* sidechain, where sidechain control signal = input signal.
If you cannot find a suitable quad opamp but some duals and good solder skills, you may be able to mock up a small quick'n'dirty 2xdual-to-quad conversion adapter. something like this browndog thingie: http://cimarrontechnology.com/%5Cpdf%5C070401sch.pdf

 

[tchgtr]

  OK, soldered in a socket for the sidechain IC, and fixed some pots that I damaged during dismantling. Pot surgery is soooo fun......and fixed the jumpers.
  Picked up a LM324 while getting the socket (only 50 cents) and threw it in there. Sounds pretty much like the 374, but slightly different. Similar distortion at the same levels, slightly worse HF response. Same noise. Maybe it's my massive wallwart over-driving the whole thing. Will try to replace that soon.
  I will learn to be patient and order a proper op amp. Maybe try a few.
    If I turn down the level, it stays clean and sounds pretty good, but it's not possible to match the bypassed volume without distortion...the compression is very nice and transparent, even when pushed quite far.
    But now I'm confused. While looking at datasheets and pinouts, I see that the LF374 is described as a quad op amp, not a comparator.
  Thanks for the link, but I decided to take the easy route after looking at the pinouts.
Enjoy!

 

[smallbutfine]

Yes, it's a quad, but it is not for audio at all (oops, comparator, memory is serving me bad sometimes...)
I want to guide you to another thread with more detailed discussion. http://www.groupdiy.com/index.php?topic=21177.0
If you are on the cheap side, buy some TL074, MC33079 and OPA4134 or similar, and check them in all 3 positions to find your sound.
I guess your unit is used, so check contacts on the level switches at the back, also make sure jacks are not corroded. And please use 9VAC for power, maybe the regulators deliver the noise.

 

[tchgtr]

 So...last night I opened up my ART CS2 out of curiosity, to see how similar it was to the 3630. I got this a few years ago because the owner only wanted $25 for it with the original wallwart (9v 800mA). It seems similar to the 3630 because it also has the gate after the comp, and other similar features. It never distorts like the Alesis, but I didn't trust it, and have used it on tracks that were not so out front.
  I've never been able to find a manual or schematic, and info on the web is quite scarce.
  Imagine my surprise when I opened it up and found two MC33079, many TL074, two THAT 2150, film caps in the signal path, and lots of 1000 and 2200 uf caps in the PSU. The circuit board says 1994, so my hat is off to whoever designed this puppy.
  I will reevaluate it and give it some better tracks to chomp...
  Thanks again Martin, I really appreciate your help!
   My 3630 seems OK, though the pots feel like someone used solder flux to clean them. That's why I pulled two apart getting the knobs off.
Will put a photo of the CS2 below...

 

[analogguru]

So...last night I opened up my ART CS2 out of curiosity, to see how similar it was to the 3630.

Imagine my surprise when I opened it up and found two MC33079, many TL074, film caps in the signal path, and lots of 1000 and 2200 uf caps in the PSU. The circuit board says 1994, so my hat is off to whoever designed this puppy.

Why are you surprised ?
When MXR busted in the mid-80´s they split into two groups. The people around Keith Barr founded Alesis and the people around Richard Neatrour became ..... ART.

The first units they sold were even 1:1 MXR products like the ART 172/174 EQ´s or the Alesis XTc Reverb.

analogguru

 

[tchgtr]

AHHHHHHHHHH YESSSSSSS!!!!!!!
Part of my problem was a mistake a I made in my power supply fix. Shoddy solder joint and bad cap choice.
Patting myself on the back for getting out the DMM and working out.
+ and - voltages were way out of balance.
Found a TL074 today and threw it in. Now we're getting somewhere. Will play with some ICs later---just wanted to hear for myself that it was worth the time. Agree with Martins' assessment of the TL084s tone. A bit grainy, but workable. Will definitely try his other suggestions.

A few discoveries to pass on:
A GNX3 power supply works fine. 9v 2A Even the jack is the right size.
Digikey lists TLE2074 and 84, though they are out of stock at the moment. About 6 bucks a pop.
Maybe some 22uf bipolars on the input? Anybody try this?

Anyway, this thing is MUCH nicer now and a good project at incredibly low cost.
Thanks butta, wherever you are...

 

[audiovisceral]

I keep thinking I'll get around to adding a simple balancing stage on the output to increase my overall output level, but just haven't got around to it yet.  

I picked up a 3630 myself for modding a while back and though I haven't got around to it, I considered doing that as well. If I understand correctly, the only thing you'd need is one of these balancing cards from Gustav.

http://www.groupdiy.com/index.php?topic=29333.10
http://www.groupdiy.com/index.php?topic=10776.0

The issue though is I'm not sure there would be room for it. Can anyone who has one confirm whether it would or not?

Also, I think the current TS input/output jacks are PCB mount so it might be tricky wiring some real sockets in there without interfering with the board again.

For power, I guess you would just run an extra set of wires from the beefed up AC adapter (Line 6 PX2) jack to the balancing card?

 

[smallbutfine]

I guess there is no proper way to cram balancing stages into this small box.
I even thought about giving the whole thang a new case, but since I wanted to keep all those nice controls and meters, it would'nt be easy.
In such a small case, maybe a THAT or SSM balanced line driver output on a very small output pcb between the upper and lower pcb + a stereo jack that does not interfere with the lower pcb would be the only chance to do nice balancing inside of this box. It could work.....

@tchgtr:
Nice you got the distortion issue fixed! Do not expect TL074, TL084 and TLE074 to sound too different from each other in terms of sonic fingerprint. I think I cannot distinguish TL074 from TL084 by listening at all. They are essentially the same thing, only one time unity gain stable and one time not. Maybe try a OPA4134 or 4132 if you want to stay in TI's league. If you can find MC33079, those are cheap and a clear upgrade if you like it more clean and neutral. Maybe the best bet before you invest into much pricier opamps. I tried out OPA4227 and OPA404 mainly because I had a small stock of them at home and read others were satisfied these in the 3630.
There was a similar mod done to the older Behringer compressors that I did too. I think Hank came up with this. Only upgrading power transformer, upping input voltage to +-18V by changing the regulators and replacing 4 quad opamps to nice ones that can stand 18V. Unfortunately, dissoldering the pcb is much more work and everything but easy.
The topology of some of those cheaper unit's designs is pretty good, just the implementation lacks from cheap parts choice and degrades sound quality alot.

 

[mitsos]

In such a small case, maybe a THAT or SSM balanced line driver output on a very small output pcb between the upper and lower pcb + a stereo jack that does not interfere with the lower pcb would be the only chance to do nice balancing inside of this box. It could work.....

I've used the THAT 1646 on the output of a 312 pre (instead of a trafo) and all I did was stick 2 10uF bipolar lytics on the output pins. Would fit on a 1 inch square piece of veroboard.

 

[analogguru]

The issue though is I'm not sure there would be room for it. Can anyone who has one confirm whether it would or not?

There is enough room inside for a small pcb with a dual opamp (two inverter stages). You don´t need more, when you forget the -10db switch.
Even a balanced input can be made then easily.

Also, I think the current TS input/output jacks are PCB mount so it might be tricky wiring some real sockets in there without interfering with the board again.

I have a Rev. D and the jacks are standard Cliff. Exchange them with a stereo version and cut or bend the legs of the tip.  Solder a wire to the ring contator and wire it to the inverter stage (or the input op-amp).
[/quote]

analogguru