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USB Oscilloscope for Audio Work

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I've seen this discussed a few times, probably here on PSW, but can't find what I'm looking for using the search engine.

I'm considering adding a USB scope module to the bench.  Seems like a 4ch setup would be real nice for amp testing.  Run both channels on a dummy load and be able to compare input to output.

As well testing DSC's to ensure they are doing what they are setup to do.

Anybody have any experience with these?  Which brands, etc?

A stand alone could be simpler overall:


Chris Grimshaw:
I don't know how useful it'll be, but there's a scope built into REW (NB - I'm using the Pro version, can't remember if it's on the free version) which seems to work fine. You'd be limited by the input of your audio interface in terms of sample rate etc. While my (old, analogue) scope runs at 20MHz, my audio interfaces run at 192kHz. Quite the difference.

Curious to see what you end up with.


I'll give it a look, seems like I have REW on one of the laptops.

Riley Casey:
The Metric Halo Spectra Foo software has an Oscope function.

Frank Koenig:
In the absence of any specific recommendation (sorry) the first question I think is whether the input characteristics of an audio interface are sufficient or if you need conventional oscilloscope inputs. (I know you know this but I'll spew a few thoughts for my own benefit, if no one else's.) Scope inputs have bandwidth sufficient to show spurious oscillations, RF interference, etc. They typically have 10 M Ohm input resistance with a small shunt capacitance, have built-in ability for AC coupling , low-pass filters, a wide signal amplitude range and compatibility with probes that provide accurate transient representation. They are far more tolerant of out-of-range signals that might toast an audio interface.

An audio interface, on the other hand, will have finer amplitude quantization, which allows distortion and noise measurements, and is perfect for balanced mic and line signals.

For amplifier testing you'll likely need two inputs per amp channel since amp outputs cannot be relied upon to have one side grounded. The app should have the ability to subtract the signals from one another to create a differential input. (There are other ways around this, such as using a transformer, but that introduces its own aberrations.)

I'd take a hard look at the app. The finest piece of hardware won't matter if the app is unusable. Also cross-shop with stand-alone scopes. For a little more money you can get a "real" scope that will never want to update its OS right when you actually need to do something  >:(

Good luck and tell us what you end up with.



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