Choice of oscilliscope

[Salas]

O-scope is no very useful for audio (analog neither digital) - i mean it is OK to quick and visual verification but nothing more (thing that can be useful in DSO/DPO will be FFT spectrum analyzer - however dynamic is quite low and limited approx to 40 - 60dB max).
Buy decent audio card (Firewire/USB) which is able to sample signal with 192ksps or higher - this will be definitely more useful for HiFi and can be used side to normal oscilloscope.
I always impressed about people that use 8 bit (at best 10 bit) quality sinewave generators with analog/digital scopes that usually provide less than 50dB dynamics to evaluate their precious 24 bit design.

You are talking spectrum analyzer duty now. That is another thing and there exist dedicated instruments for it. Of course we use 24bit cards for that (strictly good for just the audio bandwidth+few octaves, they fail hard beyond). See attached examples for a preamp of mine when using audio card and PC as SA. On the other hand the scope is the single most useful instrument for all electronics design and debug. Try see if your amp is stable, if and why it rings somehow, helpless if without a scope. Or try debug a DAC for data transfer or layout contamination. Has little to do with THD and dynamic range, scope is a time machine. It captures events. Has to do with rapidness. That is why they keep the bits low relatively to other machines, they try to make them as near real time as possible.

 

[samoloko]

Salas
Is that plot from 24 bit card or from your pre
what brand Is your card

 

[Salas]

EMU tracker pre looping through an old op amp line pre of mine. 1991 design. Repainted and fixed up in 2011. Belongs to a a friend and former neighbor for few yrs now.

 

[samoloko]

thank you
I wonder how you get such a great noise In a noisy PC