[sdiy] Any noise avantage to parallel 2164 VCAs?

Tom Wiltshire tom at electricdruid.net
Sun Jun 17 22:31:25 CEST 2018


I don’t think it’s any extra C and Rs at all. Like Ian said, thew them together pin for pin. I don’t see the point of hanging two RC networks off one combined input, so there’s nothing extra there. I suppose you could use separate 30K input resistors and RC networks for the two inputs, but why?

We know from the datasheet that the outputs can be tied together, so there’s no problem there.

Control input impedance is a reasonable point - the 5K impedance isn’t high to start with, and will get lower, but it’s still at a manageable level. So I don’t see a problem there either.

Tom

> On 17 Jun 2018, at 15:28, Mattias Rickardsson <mr at analogue.org> wrote:
> 
> Definitely, use them in parallel. The VCAs are easily the noisiest bottlenecks of your circuits and using two in parallel should lower it around 3 dB.
> 
> I don't see how it wouldn't be worth the circuitry - what is it, an additional C and two additional R?
> 
> Also, make sure to use the new improved SSI2164 for even better SNR and/or THD potential.
> 
> /mr
> 
> On Sun, 17 Jun 2018 at 13:49, Tom Wiltshire <tom at electricdruid.net> wrote:
> Hi all,
> 
> A quick query, if I may: Is there any noise advantage to using two 2164 VCAs in parallel?
> 
> I’ve got a circuit that uses two VCAs, so there are two others spare on the chip. And then it occurred to me that there might be a minor gain by using them in parallel pairs. It’s a case of “well, they’re there so we might as well use them” if there’s no reason not to.
>  Or would it be better to simply disable the unused sections?
> 
> Thanks,
> Tom
> 
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>        Electric Druid
> Synth & Stompbox DIY
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> 
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