[sdiy] Coolaudio VCAs: V2162 noisier than V2164?

[Mattias Rickardsson]

Hi Chris,

I'm using a MOTU UltraLite Mk3 Hybrid sound card and Arta software on a PC.
The 2164 and 2162 have I/V converters built from a NE5532 low-noise op-amp.

I've tried to eliminate all sources of stupidity (except myself) and
compared different ways of disconnecting & comparing the sources of
noise. With the 2164, the generator (MOTU) is noisier than the VCA,
which is noisier than the op-amp, which is noisier than the analyzer
(MOTU). With the 2162, the VCA is noisier than both the generator, the
op-amp and the analyzer. I've also tried to eliminate all noise on the
CV signal and tried to avoid HF oscillations.

Is the 2162 used by anybody or in any product out there?

/mr



On 21 December 2015 at 17:40, Chris Juried <cjuried at yahoo.com> wrote:
> Hi Mattias,
>
> What instrument(s) are you using for you SNR measurements?
>
> Sincerely,
>
> Chris Juried
> Audio Engineering Society (AES) Member
> InfoComm-Recognized AV Technologist
> http://www.JuriedEngineering.com (Juried Engineering, LLC.)
> http://www.TubeEquipment.com (Tube Equipment Corporation)
> http://www.HistoryOfRecording.com (History of Recording)
>
>
>
> ________________________________
> From: Mattias Rickardsson <mr at analogue.org>
> To: synthdiy diy <synth-diy at dropmix.xs4all.nl>
> Sent: Monday, December 21, 2015 10:21 AM
> Subject: [sdiy] Coolaudio VCAs: V2162 noisier than V2164?
>
> Hi there VCA lovers,
>
> I've done some measurements of SNR & THD of the 2164 and 2162 VCA ICs
> from Coolaudio, and I'm very surprised with the noise results I'm
> getting. With the 2162 I cannot reach a SNR over 95 dB before
> clipping, at any gain. With the 2164 at gain=1 I reach 120 dB SNR.
> That's a huge difference!
>
> When trimmed properly the 2162 does have slightly better THD, but the
> noise seems to always be there in the background. I hope my
> measurements are correct... the "-97 dBV" noise spec in the V2164
> datasheet seems a bit odd to me compared to the "-94 dBu" in the V2164
> dataheet - or I've misunderstood them.
>
> Has anyone else tried the 2162 (either from THAT or from Coolaudio)
> and compared it to the 2164 or other VCAs?
>
> /mr
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