scott2000

Re: Coolaudio ICs ??
« Reply #20 on: December 01, 2019, 06:27:54 AM »


Any of you ever experimented with V2162 or V2164 vcas?

Replaced with one (V2164) in a Mackie SRM450 amp...... seemed to work......
That amp went goofy again after about 6 months....haven't looked into why.... ended up going passive crossover on them....


porkyc

Re: Coolaudio ICs ??
« Reply #21 on: December 07, 2020, 02:09:49 PM »
I appreciate this is an oldish thread but,
Going back to the original discussion.
For a variety of reasons, I’ve made a couple of versions of replacement VCA cards for a particular console, one using a single THAT 2181B and the other using the 2164 chip as 4 parallel units running in Class A. The self-build aspect was important, so I stuck with the DIL version V2164. Picture of boards attached.
Both boards use a 5534A as the I-V O/P chip, and a TL071 as the local control scaling buffer. It might be fairer with an untrimmed 2180 chip, but I had the trimmable version to hand.
As a reference, I’ve included test results for a black dBx202 board and a third-party replacement board for those, by B&B Audio. I also had access to a Coolaudio V2181.

Results:-

Test Criteria   dBx202   B&B Audio   THAT 2181B   V2164        Cool V2181
Distortion               
Unity gain SMPTE IMD 0dBV   0.03%   0.01%   .007%   .058%   .031%
Unity gain THD+N 1Khz 0dBV   0.01%   0.01%   .012%   .021%   .014%
               
Noise               
Noise (rel 0dBV) 20-20Khz BW   -90dB   -90dB   -95dB   -91dB   -93.5dB
Noise (rel 0dBV) CCIR-468   -83dB   -84dB   -88dB   -84dB   -87.5dB


0dBV is the reference level used in the THAT specifications.
On CCIR 468 filter for noise; if it’s noisy with that, it is!
On SMPTE IMD, I know some people pooh-pooh this, but it is still an indicative test, and more revealing than THD+N, ie it becomes far more entertaining if you ask DUT to do two things at once.
The measurements were taken with a Neutrik A2, the noise figures verified with a Sennheiser 550A UPM.

So the quad 2164 configuration is no better than a 40 year old dBx202, the VCA that has been considered unacceptable in low noise, low distortion console applications for some time!
The Coolaudio V2151 is good on noise, but again, just matches the black 202 for distortion, but is cheaper.
But for the price, the choice would be the THAT 218x stuff; meets its specifications, the 2164 does not, or at least not in the configuration recommended. The configuration could be worked on, I suppose, but would you get down to 0.007% SMPTE IMD? I doubt it.