[sdiy] Outputs and Impedances

Tony K weplar at gmail.com
Fri Oct 26 06:01:06 CEST 2018


If you look on monosynth schematics manufacturers often used 1 K resistors to feed subsequent stages. as load resistors. Especially some sort of signal mixing was desired ( transistor circuits without op-amps did used this cost cutting measure see early Roland drum machines for example) 

TK

> On Oct 25, 2018, at 11:00 PM, mskala at ansuz.sooke.bc.ca wrote:
> 
>> On Thu, 25 Oct 2018, Youssef Menebhi wrote:
>> Sorry, but I just need to clarify the exceptions:
>> The idea is that the "inputs" that are being fed by the output of the
>> single op-amp will serve ultimately as outputs from the device.  So,
>> buffers are needed?
> 
> If there are voltage dividers between the op amp output and the outside
> world, that's probably going to be enough to prevent the outside loads
> from affecting each other through the op amp output.  What I was
> imagining as a problem would be if you had something like the op amp
> output connected *directly* to an output jack, and also to internal
> stuff - in that case, someone plugs a short into the output jack and then
> no signal gets to the other internal destinations either.
> 
> But what are you actually building?  Some sort of interface?  Are you sure
> your voltage dividers are going to present the right impedance to the
> outside world?  That seems to me more likely to be an issue than the
> internal connection between the op amp and the three voltage dividers,
> which would normally be just a wire and not require any special design
> of its own.
> 
> -- 
> Matthew Skala
> mskala at ansuz.sooke.bc.ca                 People before tribes.
> http://ansuz.sooke.bc.ca/
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