[LAU] Soundcard Oscilloscope

[Ede Wolf]

Am 22.03.2018 um 22:00 schrieb Will Godfrey:
> Which rather begs the question, why are almost all digital scopes only 8bit...
> unless you spend a fortune on them?

Bandwidth (or rather sample rate). For probably most applications an 
oscilloscope is used for, audio being one of the few exceptions, 
bandwidth is usually more important than resolution and a higher 
bandwidth requires a higher sample rate to be of any use.

Also, higher resolution requires higher quality frontends, that 
naturally get more and more expensive with increasing bandwidth.
You'll hardly find any affordable scope with remotely that noiselevel of 
a good soundcard.

Further there is naturally a significant difference in data between 
192kHz and 1GS, latter being quite the standard these days, and that 
amount of data needs to be handled somewhat accurately by the AD 
converter as well as the processing backend.

So to keep the amount of data managable, you reduce resolution, or 
increase the price.

Anyway, I am unaware that there even is such an AD converter to handle 
1GS/16bit+ at all. Anyone?


But even for audio I would assume, resolution is more important for fft 
analysis than for an oscilloscope - though it is not uncommon that a 
device does both, with of course a lousy front end unless you really 
spend cash.
But, if capturing signals is really needed, like oneshot, 8 Bit, while 
not a beauty to look at, is usually sufficient for analysis. For 
everything else there are analog scopes to be had for cheap these days.


There are a few DC coupled soundcards out there. A company called expert 
sleepers is selling devices, that make control voltages for analog 
synthesizers controlable from (windows) computers, in turn requiring DC 
coupled soundcards.
In that context I believe to have read some discussion about that. Maybe 
that helps as a starting point.

But, as already said, mind your inputs. As a matter of principle always 
starting out with a 10x probe (there are adapters) would be really 
sensible behaviour to get used to, if no input protection is in place. 
And a spare soundcard, just in case...