[sdiy] Using SSM2164 in stereo

[cheater cheater]

I guess the point would be that the separate RC networks would
stabilize the currents separately so that the input impedances of the
vcas would not influence eachother. The question is what's going to
degrade worse over time: a self-built RC nework, or a 2164.

I think depending on what parts you use around the 2164 the answers
could be both ways, but at the point it's justified to use two
different RC networks maybe you're spending too much money, too much
time, and you probably know enough about electronics to build
something better than a 2164. This is however speculation and the
point at which two RC networks are feasible could be much lower in
price and effort cost.

D.

On Wed, Jan 20, 2010 at 19:58, David G. Dixon <dixon at interchange.ubc.ca> wrote:
> Tom, I don't see what you would gain by having two sets of stabilizing RC
> networks in parallel.  Just split the currents after the network, and you
> should be fine.  The VCAs are very well matched, so each VCA should get the
> same amount of current.
>
> The 2164 is notorious for exhibiting very high frequency oscillations when
> it's gain is pushed much above 1, but if you are using it only as an
> attenuator (i.e., you never expect the VC to be less than 0V), then you
> should be fine.
>
>> A quick query about the SSM2164;
>>
>> I'm designing a dual stereo VCA based on this chip. Each input is fed
>> to a pair of VCAs, which control the Left and Right signals for that
>> channel. The two Left outputs and two right outputs are reunited in
>> the I-to-V amp after the SSM2164. This makes the whole design one
>> SSM2164 and a dual op-amp.
>>
>> The datasheet shows each VCA input with a 500R and 560pF cap to
>> ground. If I'm tying two channels together, can I dispose of one set
>> of R & C? might I need to tweak the values a bit to ensure stability?
>>
>> The VCA will be fed by a current output, so I don't have the 30K
>> input resistor that the datasheet also shows.
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>