[LAU] Soundcard Oscilloscope

[Sean Bolton]

Hi Will,

On Thu Mar 22 2018, Will Godfrey wrote:
> Has anyone got any experience of these?
> Are they in fact any good?
> 
> I would imagine that running one at 96k, 16bit should give a good
> enough bandwidth and resolution for checking most audio kit.

They're certainly better than no oscilloscope, but not as good as a
real one.

Almost certainly your soundcard is AC coupled, meaning it has
capacitors in the input path to block any DC signal. There are some
guides online describing how to remove the caps on certain soundcards,
but I've never tried it.

If you're going to be poking around anything but the tamest stuff, you
might want some input protection to avoid smoking your soundcard.
Again, there are lots of guides online about building a input stage,
usually with pairs of diodes to protect against (moderate) overvoltage,
and often with a higher impedance, so your measurements won't affect
the circuit you're measuring as much.

I really like having good probes designed for the job, instead of
alligator clips or bare leads. You could put some BNC connectors
on your input stage, and get some inexpensive probes online.

I would recommend that, if you think you'll use a scope more than
just occasionally, and you're not on a really restricted budget or
just want to play around with soundcard-based solutions, you'll be
better off just going for something like the Hantek 6022BE: 2 channel,
20MHz bandwidth, DC coupled, high impedance inputs, comes with real
probes, supported by OpenHantek and sigrok on Linux, for only $60US or
so.

Whichever way you go, have fun,

-Sean