[sdiy] Patch pal style audio amp

[Quincas Moreira]

Hey Joe, if you want it standalone and battery powered you can use two 9v
batteries wired as a dual supply. But that will only get you to about an
+/- 8v swing depending on which opamp you choose. Might be enough, try it!



On Sun 17 Jul 2022 at 23:04 brianw <brianw at audiobanshee.com> wrote:

> A single transistor circuit is really only going to work well for a signal
> like Gate, where it's just On or Off, and you use the transistor to change
> the voltage or even invert the polarity.
>
> For an audio signal, a single transistor is either going to give you very
> low quality, or require a good number of support components that will have
> to be carefully designed to avoid distorting the audio. This is not the
> easy route.
>
> BBob's recommendation to use op-amps is, by far, the easiest. This is
> exactly why the op-amp was invented. You can even buy a dual op-amp in a
> single package. These will run off batteries, but you might want to select
> low-power op-amps and adjust the circuit to deal with any tradeoffs or
> headroom differences.
>
>
> As for your applications, you might find that you need two different
> solutions:
>
> E) The desktop modular is going to take ±10V peak-to-peak audio, or maybe
> half that amplitude. This is the one where BBob's gain recommendations
> should be spot-on.
>
> D) The desktop synths might not expect modular voltage levels, so you
> might distort the audio input when feeding the synth with boosted levels
> intended for modular. In my admittedly limited experience with synths that
> have audio *input* (samplers), the expectation is usually for line level
> audio. It's very likely that each synth will be different. There's not
> necessarily any standard audio input level for desktop synths. If you tell
> us more about your desktop synths, it might be possible to find out what
> audio input levels are best.
>
> Brian
>
>
> On Jul 17, 2022, at 8:14 PM, frey at radioles.com wrote:
> > Tx for the reply. I am going into desktop modular device that’s eurorack
> spec. I am coming out of a Crudman voltage controlled cassette player into
> a EOWave Quantrantid Swarm. I have a few desktop synths that I want to run
> audio into in this way, not an actual eurorack spec powered case.
> >  I have a bunch of passive patchpal thingies in the style Quincas has
> built. I want to make something self contained so batteries because not
> passive. I have seen amp circuits using one transistor. Could this work?
> JoeF.
> > On Jul 17, 2022, 10:37 PM -0400, bbob <fluxmonk at gmail.com>, wrote:
> >> I use 2 inverting op-amps in series, with a gain on the first one at
> about 5 (since you're in eurorack, you already have a dual power supply)
> >>
> >> On Sun, Jul 17, 2022 at 10:25 PM JoeF <frey at radioles.com> wrote:
> >>> Hey there all, I bet someone has already made a small battery powered
> amp to go from line level to a hot input signal for Eurorack modular
> standard?
> >>> If not, then can a I use a single transistor amp to do this? Will the
> input drag it down or load it up? TY for any advice or help. JoeF.
> >>>
>
>
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-- 
[image: QMA]

Quincas Moreira
Director | QMA
mobile:  5534988825
site:  quincasmoreira.com
email:  quincas at gmail.com
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