Subject: Re: [linux-audio-dev] [ann] unmatched - a LADSPA amp tone
From: Lamar Owen (lamar.owen_AT_wgcr.org)
Date: Tue Oct 29 2002 - 20:51:21 EET
On Monday 28 October 2002 05:33 pm, Steve Harris wrote:
> On Mon, Oct 28, 2002 at 10:37:18 +0100, Tim Goetze wrote:
> > it shows my badly-driven fender amp's line output (top) vs. the sine
> > wave it was fed at the same time. i'm wondering how come the output
> > overshoots every time the input crosses zero. trying to model this
> I dont think it does, I still think this is just a phase effect.
> OTOH it could just be an extreme case of hard clipping and HP filtering.
I would lean this way as well, since the first interstage coupling caps are a
mere .02 microfarads. Even at the circuit impedance there, you will have
some serious overshoot due to the series capacitance.
See the SPICE project for a circuit simulator program that can handle
waveforms in this sort of circuit. SPICE is as old as dirt, but a very handy
program for electrical engineers. The algorithms used in SPICE, once you
have a working netlist, could theoretically be used on audio waveforms, but
it would take a real machine to get realtime results through SPICE. The nice
thing about SPICE is that, if you have the curves for the active devices, and
the schematics for the circuit as a whole (which is the case here), you can
model very accurately the circuit in question.
To find SPICE, search virtually any archive of freeware in the engineering
programs section. SPICE is the Csound of electrical engineering.
-- Lamar Owen WGCR Internet Radio 1 Peter 4:11
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