Re: [linux-audio-dev] [ann] unmatched - a LADSPA amp tone

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Subject: Re: [linux-audio-dev] [ann] unmatched - a LADSPA amp tone
From: Frank van de Pol (fvdpol_AT_home.nl)
Date: Tue Oct 29 2002 - 01:18:23 EET


On Mon, Oct 28, 2002 at 10:37:18PM +0100, Tim Goetze wrote:
> i'm sure frequency responses and Vin/Vout mappings for common
> amp tubes (EL34 comes to mind, too) would be very helpful, but
> can i ask you to take a look at
> http://quitte.de/driven.gif
> first?
>
> 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
> behaviour into a waveshaper, but i'm a bit lost on the physical laws
> that rule here.
>

looking at the distorted signal it look to me like an amp that is clipping,
but it's power supply can't maintain the voltage (eg. relatively high
impendance on the powersupply/series resistance). While +ve or -ve side of
the output pair is used it drains the capacitor from the power supply, hence
the exponential slope from 'spike' till drop.

Frank.

-- 
+---- --- -- -  -   -    - 
| Frank van de Pol                  -o)    A-L-S-A
| FvdPol_AT_home.nl                    /\\  Sounds good!
| http://www.alsa-project.org      _\_v
| Linux - Why use Windows if we have doors available?


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