Subject: Re: [linux-audio-dev] Diode wave shaper (LADSPA plugin)?
From: Jens M Andreasen (jens.andreasen_AT_chello.se)
Date: Mon Aug 16 2004 - 19:23:06 EEST
On mån, 2004-08-16 at 16:49, Stanley Jaddoe wrote:
> The 12k resistor is just an example, it would be nice if it would be treated
> as a variable.
>
> How can I incorporate the 1N4148 diode characteristics in the final equation?
>
One interresting thing to consider is that the diode pair is mimicking a
valve preamp, possibly with some rude Marshall characteristics.
The exact same solution can be found in the upper right corner in this
schematics, just before the tone controls:
http://home3.netcarrier.com/~lxh2/marshprb.gif
(The 1N914 share characteristics with the 1N4148)
So what you should be looking for is a valve overdrive/distortion
plugin, rather than a 1N4148 emulator.
My guess is that the *exact* characteristic is not *that* important, as
long as it has a reasonably soft knee.
> ------------------------------
>
> I did some SPICE emulation (Alfons: I know, I'm not a (real) engineer) and I
> never saw a tangentfunction-like output...
> Assuming one input and one output, (instead of the shown three inputs in my
> first post), if the input signal is a triangle wave, I should get a (not
> perfect) sine wave.
For some value of 'not perfect', yes :)) Crank up the volume and it
should transform into a square, apply a second channel with LFO and you
get pulse-width modulation.
Now please tell us, what is this synth of yours that you have
disassembled? Is this circuit part of the output-stage or is it part of
the individual oscillators? Inquiring minds wants to know!
/jens
>
> ------------------------------
>
> BTW: Does anyone on this list has any experience converting an analog hardware
> synth to a softsynth using the synth's schematics?
>
>
> Stanley
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