3630 mod meta

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edanderson

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Joined
Jun 4, 2004
Messages
637
Location
atlanta
for a while at least, matt over at black lion audio was doing a pretty extensive mod to the 3630. he seems to have dropped off the internet a little while back, but here's a cached link to his old page on the 3630 mod:

http://web.archive.org/web/20031211030834/http://www.blacklionaudio.com/alesis_3630_modifications.htm

he used to go by the handle "puffpastry" on the tapeop board, but changed to "lebowski achiever" at some point. anyway, a search over there brings up some info on his work.

ed
 
Just a quick comment.... while researching the info available on the 3630, I saw where it was repeated numerous times something to the effect that the LED meter sucks current and causes audible glitches.

Not so. The LED meter string on the 3630 is powered by a constant current source, so the power draw is the same whether there is one diode lit or all of them.

regards, Jack
 
I saw where it was repeated numerous times something to the effect that the LED meter sucks current and causes audible glitches.

Not so.

Yes, there is a lot of false presumptions floating around. The power for the LED section is also routed directly from the regulators in order not to influence the audio part.

Other has claimed that the 3630 rolls of the high end, but it's actually flat to about 70 kHz even at 12 dB gain reduction.

/Preben Friis
 
To my eye (staring at the schematic) it looks to me like the general suckiness of the 3630 might come from the attack-release circuit and the rather strange comparator setup on the tail end of the CV chain. Having an unbalanced input can be a pain depending on where you patch it (such as as an emergency (singer without enough studio experience) compressor while tracking or that sort of thing). The RMS detector might be a bit underbiased, though it is well within the operating range of the chip. I prefer the LM837 (quad LM833) in place of whatever opamps they seem to use, but if you do this you need to watch the decoupling and loading of these amps - they oscillate easily.

Basically, they used a comparator as an op-amp in several places and that's not a good thing. They are not designed to be unity-gain stable and would have a tendency to oscillate in that configuration.

There also appears to be at least a few revisions of the 3630 - I have three of them and the schematic and parts values don't match between them!

-Dale
 
After reading through this fine information I cracked open my 3630 and discovered that it already contains THAT 2252's and other THAT chips in place of the 2180's (I want to say the number was 2150 but I don't have it right here in front of me - not 2180's either way). They definitely look to be original - machine soldered rather than hand. I'm going to put the Burr Browns in but I was curious if Alesis saw the light (or half of it anyway) somewhere along the line.
 
that schematic link above is dead..

has anyone saved it and can put it up again, or send it to me via mail??

that would be very nice....!!!


thank you...
matthias

 
Wanted to mention that I recently tried basically the Butta mod to a rev.D and had a coupla comments...

It appears to me that U4 does not pass signal THRU it. I think it only works the gates. I don't have a schem, but maybe someone that does can confirm. In that case, I left the LF347 in place and installed OPA4134 in the other two locations.

When I got it back together, I had no o/p on one channel. Traced that down to a faulty +4/-10 switch and until it was corrected, it seemed to introduce some distortion, so I wanted to recommend replacing those with jumpers.

HTH!
Charlie
 
:razz: Nice one, Charlie, the switches are crap. I had to struggle with them one time and never bothered to change the output again, so i never came to this idea...
How does it sound to you after the mod?

Kind regards

Martin
 
Hi,
Just got motivated enough to do this mod to my 3630's. Somewhere on the net I had read that the Line 6 PX-2 was the PS to get for these. I ordered a couple, and it turns out they plug right into the original PS socket on the board, no need to swap out that part. They are 1.5 watt, 2000ma, 9vac, and theere are Part #'s for US, EU, UK, AU and JP. Got mine for under $20 each, plus shipping @ zzsounds. Nice and Beefy in line wart.
I wish I remembered who to credit for this tip (or what board I read it on), but Thanks a Lot :guinness: :guinness: :guinness: :guinness: :guinness: :guinness: :guinness: :guinness: :guinness: :guinness: :guinness: :guinness: , and I hope this helps others.
mrc
 
Hello! First posting...there are a few MC33079 chips available with different suffixes...Which on to choose? thanks for the mod I own three and love to pull things apart. But not like the bad boy on Toy Story...
 
Sorry to bump an old thread, but since BlackLion doesn't offer the 3630 mod anymore their instructions for the mod were floating around (I had it and lost it). Does anyone have a PDF of this they can provide?
 
therecordingart said:
Sorry to bump an old thread, but since BlackLion doesn't offer the 3630 mod anymore their instructions for the mod were floating around (I had it and lost it). Does anyone have a PDF of this they can provide?

I wouldn't mind a copy as well if anyone can deliver.  :)
 
Well, I never had a look into the blacklion mod and always wish I had since it disappeared from the web. Just to see it in detail, for comparison with my own experiments.
So I would be in that *me too*-row, too...
 
How weird that this thread popped up! I modded a 3630 with the Black Lion kit back in 2004 or so...I got sidetracked with other builds..LA2a's, 1176's etc and the 3630  just sat..YESTERDAY I pulled it out and ran a few vox thru it and was really impressed. I am going to experiment more with it today...I have the original instructions somewhere but I will be out of town for the next week or so..if I can find them I will let you guys know....As far as I remember you upgrade many components and totally replace the vca and quad opamp then rebias the circuit for the new pieces...


Ray
 
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