pucho812 said:
well if you ask me, if it was working to your liking before, then why mess with it.
The 3630 is widely known to sound bad and i on a number of times when using it found it to be a bit harsh and no where near as smooth as my other comps... Some people actually liked it for its lo-fi sound but if you change out a few of the op amps, power caps and diodes you can get it to sound clear and soft........I was wondering if anyone had listened to what kind of difference a modded 3630 and a newer 3632....
Anyhow seeings that me and my mate both have exploded 3630's, they are getting modded following this guide.......
smallbutfine
Member
Posts: 762
Northern End of Germany
Re: 3630 mod meta
« Reply #24 on: April 01, 2010, 03:35:04 AM »
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@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
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