[sdiy] Quick query about 2164 VCAs

Tom Wiltshire tom at electricdruid.net
Mon Mar 18 00:47:21 CET 2019

Good point well made. The CV may be crucial. While we’re talking about suspicions, I suspect that the different CVs might be what sinks my idea.

I’ll do some experiments and let you all know what I find out.

> On 17 Mar 2019, at 23:06, Neil Johnson <neil.johnson71 at gmail.com> wrote:
> To be more precise, paralleled ins, outs and CVs - as shown in the
> datasheet - works.
> Neil
> On Sun, 17 Mar 2019 at 22:58, Neil Johnson <neil.johnson71 at gmail.com> wrote:
>> Hi Tom,
>>> What makes you think that:
>>> A) this parallel-inputs-independent-outputs arrangement only works if the CVs are identical?
>> Looking at the schematic shown in the SSI2164 datasheet and
>> considering the various current paths within it I have a strong
>> suspicion that unless the currents in the VCA bit are balanced between
>> the gain cells then any imbalances due to different control voltages
>> will cause the inputs stages to behave differently, and so the input
>> current will not be shared equally between the gain cells.
>>> B) the outputs have to be paralleled too?
>> That's a less certain hunch, and I may be wrong, or right ;)  The only
>> real way to test this would be to build it and try it out.
>> What I do know is that paralleled ins and outs does work, as I have
>> that working on the bench.
>> Neil
>> --
>> http://www.njohnson.co.uk
> -- 
> http://www.njohnson.co.uk

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