On Sun, 4 Apr 2010 01:55:47 +1100, "Phil Allison"
wrote:

** DO NOT BUY A DIGITAL SCOPE !!!!!!!!!!!!!

Why?

Almost any ANALOGUE scope with bandwidth of 5 MHz or more is OK - DC
coupled or not.

Digital scopes absolutely SUCK for audio work.

Why duz it suck?

I don't do much audio work. Just the audio processing sections (mic
amp - compressor - limiter - modulator - demodulator - demphasis
- speaker amp) of two way radios. The ability of digital scopes to
do the grunt work of sweeping the frequency and amplitude range,
measuring SINAD directly, and frame grabbing the results, have been a
big plus. I may not be able to see distortions, high frequency
ringing, and subtleties because of the dynamic range limitation of the
A/D converter, but everything else is much better and easier. If I'm
looking for high frequency oscillations, I use one of several 100Mhz
scopes. If you have the money, I would get both a digital and an
analog scope.

Article on the limitations of digital scopes:
http://www.syscompdesign.com/AppNotes/scope-specs.pdf

So despite the unsubstantiated warnings of digital doom and disaster,
I'll recommend Visual Analyzer:
http://www.sillanumsoft.org/prod01.htm
for a (free) PC based software oscilloscope. This is what I use for
most of my tinkering and light weight waveform sniffing. It should
give you a clue as to the limitations of 8bit 44KHz (or 24bit 96KHz)
sampling PC based scopes. With a 24bit sound card (Startech 7.1 for
$20), I can see noise down to about -80dB (-120dB theoretical) below
max input.

For a USB scope, this is my current favorite:
http://www.syscompdesign.com/CGR101.html $200.
Note the open source software. The only problem is that I share it
with a friend and don't quite own it yet.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558