Re: DOD even harmonic---clipOn Feb 28, 4:59 am, Rob <R...@nospam . com > wrote:
> On 25 Feb 2007 21:48:38 -0800, "RichL" <rpleav...@yahoo . com > wrote:
>
> >On Feb 25, 5:13 pm, Jim <a...@beforeyousend . com > wrote:
> >> "One of these days" I'll post snapshots of my oscilloscope screen
> >> showing the differences in waveforms of distorted amps and various
> >> pedals. It's interesting to see what your ears are hearing.
>
> >I'd like to see that. I checked that out over 30 years ago, because I
> >knew a guy with a scope. But pedals have changed enormously since
> >then. What I'd really like to see are scope captures together with
> >the pedal brands and corresponding sound files -- so you can correlate
> >the waveform with the sound.
>
> The OScope will tell part of the story. If you're looking at waveform
> asymmetry, it will be evident if you use a sine as input. And if there
> is hard clipping (usually with harsh overtones) you will usually see
> some square edges on output waveforms (not always, since phase shift
> can displace them).
>
> With a sweep generator, you could get an idea of the overall frequency
> response (by sweeping from 80 Hz to 8 Khz or so).
>
> But aside from those things, it's kind of difficult to get much more
> from a static image on a scope. The other dimensions that won't show
> up include intermodulation and other dynamic characteristics. Aside
> from mods to generate asymmetry, I'd guess that a scope image will not
> pinpoint much useful info for most current OD pedals. (I'm exempting
> stuff like the Maestro FZ-1)
>
> To get any kind of dynamic picture, you'd have to use a recorded
> waveform going in, then take a snapshot at an exact moment. There are
> pseudo-oscilloscope programs for PC that may have a better shot at
> doing that. They use the PC's sound card as the sampling engine. You
> could put a recorded waveform in one stereo channel and monitor the OD
> box on the other so they stay sync'd.
Forget sine waves, sweep generators etc. What I'd like to see is an
actual guitarist, playing with different pickups, effects, etc. with
line out from amp into scope.