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Harrison MR2 Allison VCA Automation

PostPosted: Thu Dec 11, 2008 1:07 am
by SAnthony
Currently Building a console based on Harrison MR2 Channel Strips and Master Section. I currently have an Original Melkuist Automation Computer that I may attempt to refurbish as a last resort. Can anyone tell me about a newer Computer/Software that would be backward compatable with these VCAs? Also wondering if these Allison VCAs on an MR2 can coexist with the Valley People VCAs on an MR4 Stereo Channel Strip?

THanks...Take Care,

Allison/Valley People

PostPosted: Sat Dec 13, 2008 12:50 pm
by porkyc
Are the Allison ones blue? and the VP ones green? Yes?
The Valley People TA-101 was the replacement for the original Allison Research EGC-101. Allison Research became Valley People. It was always Paul Buff anyway. Yes they are interchangeable and can co-exist. The control voltage circuit is likely to be the same. Either way, they were the best sounding VCAs.

PostPosted: Sat Dec 13, 2008 1:14 pm
by jensenmann
If you guys find or know a source for these VCAs please let me know. I could need a bunch of these for my desk.


PostPosted: Sat Dec 13, 2008 4:22 pm
by porkyc
jensenmann wrote:If you guys find or know a source for these VCAs please let me know. I could need a bunch of these for my desk.

Funnily enough, I've just been re-commissioning an MCI 500 that has TA-101s in it, and it's short of some!! I had to rob the echo returns. On another forum, somebody is considering re-doing these (TA-101s that is), I gather. Not many manufacturers used these as standard, because they were a dog to get going and be stable, but since Paul Buff was in Nashville and so were Harrison.......
No help I'm afraid.

PostPosted: Sat Jan 03, 2009 3:26 am
by tritosine
hi I beleive these are sorta matched transistors, plenty of info can be found over prodigy-pro forums.

BTW Check out my topic where I sell original ledmeters , these might be nice companion for you. 8)


PostPosted: Sat Jan 03, 2009 1:45 pm
by porkyc
Yes, they were idiotically high-frequency, high gain complimentary pairs, I believe, hence the instability.
Are those the Series10 meters? They are good, but they do need the 5 electrolytic caps changing. Be careful, the print is VERY delicate, I bought the Denon desoldering gun because I had to do about 80 of these meters recently, some of which went to a S12 console in Stockholm.

PostPosted: Sun Jan 04, 2009 2:23 am
by tritosine
well, im willing to do it in fact. Might gear up with an ESR meter as well , once i find the time!

S10/S12 meters

PostPosted: Sun Jan 04, 2009 10:16 am
by porkyc
Is the ESR meter to check the caps? Don't bother, just change them. Most of the problems go away, and it will leave you with the ones that genuinely don't work.

PostPosted: Wed Jan 21, 2009 5:05 pm
by Matt Syson
FWIW Calrec used the blue, green and brown versions of these critters in some of their desks but not in huge numbers since the desks they were building at the time were mostly 'broadcast' and VCAs were not necessary.
I happen to have a couple of each...somewhere.
Matt S

Valley People TA stuff

PostPosted: Wed Jan 21, 2009 7:31 pm
by porkyc
Only the green ones can be used as VCAs because they were NPN/PNP complimentary pairs. (Logarithmic multiplier circuit). The Blue were TA102 and were all NPN, the Brown were TA103 and were all PNP. Tended to be used in transformerless mic pre amps. You would use the 2019 now, surely.
I've found all the data sheets that I had, hence smartypants reply!
Best regards