[sdiy] Quick query about 2164 VCAs

Mattias Rickardsson mr at analogue.org
Sat Mar 16 22:56:11 CET 2019


On Sat, 16 Mar 2019 at 22:07, Tom Wiltshire <tom at electricdruid.net> wrote:

> Thanks David. I couldn’t see why not either. I think I’ll go ahead and try
> it.
>

Another quick answer: I don't see why.

How could the current know that it should be divided into two equal parts?

This reminds me of the discussion last year about paralleling 2164s. I'm
using three 2164s in parallel with a separate Rin for each VCA, and
somebody said that those three resistors could be swapped against one
common resistor feeding all the VCAs. I was then asking how the current
into a virtual earth (or even worse, three less than perfect virtual
"earths" that sits on three slightly different voltages) would know that it
would split into equal halves, but IIRC there was never an answer to that.
:-)


> Do you think I’ll need to adjust (double) I-to-V resistor values when I do
> eventually go back to a voltage since I’ll be driving two VCAs with the
> same current? Perhaps that saves me from the distortion you mention. I’ll
> have twice the current coming in (two VCAs being summed) but it’ll get
> divided out to two VCAs on the output, so I finish up back where I started.
> Lordy, it’d be lovely if it was that neat…;)
>

Please try it out (with some different 2164 units if you can) and tell us
if it seemed to work. :-)

/mr
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