[sdiy] Outputs and Impedances

Mikko Helin maohelin at gmail.com
Fri Oct 26 11:41:11 CEST 2018


Also sometimes 1k resistors in front of TL07/8xs are used to prevent
phase-reversal...

pe 26. lokak. 2018 klo 7.02 Tony K <weplar at gmail.com> kirjoitti:

> 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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