Hello everyone,

In the Hans Mikelson instrument for tube distortion in the CSound Book, 90% 
of the beautiful distortion effect in instr 3013 lies on the line:

aout    deltapi (2-iduty*asign)/1500 + islope*(asign-aold)/300

Taking out this variable delay mapping makes the instrument just sound like 
distort1. Does Mr.Mikelson reads this list? Anyone could ask him to explain 
or explain himself what this deltapi formula does in detail? I could 
understand the instruments in the book so far, but I'm stuck on this one.

Thanks in advance,
Robson

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Yes, this seems exactly to be the case.

I have been looking at this instr as well, in my recent search for different distortion effects. The logic of using a slope based delay time seems clear to me, but I'm not sure I understand the (reason for the) exact formula that Mikelson uses in this instr. 
Hans, if you're there, please do enlighten us on this topic.


best
Oeyvind





> From: Aidan Collins [mr.aidan.collins@gmail.com]
> Sent: 2006-01-22 23:04:45 CET
> To: csound@lists.bath.ac.uk
> Subject: Re: [Csnd] deltapi mystery
> 
> I haven't used this orc myself, but I've been looking at it during the
> conversations in the list.
> 
> so the only argument for the deltapi is delay time. Feeding the audio
> signal into this would make the delay dependant on the amplitude of
> the audio signal. however, sedning it directly would probably not
> sound that great. However a well planned manipulation of the signal
> could make some really interesting phase distortion effects.
> It seems like the orc is saving an old version of the audio signal,
> and subtracting it from the current signal value. This could be
> considered like a rate of change parameter for the audio signal. The
> slope variable seems to control how much that change should be taken
> into effect. The duty cycle variable is probably like an initial delay
> time from which the variations would occur (but again tied to the
> value of the incoming audio.) So this way, the more dynamic bits of
> audio would cause a larger delay resulting in a distortion of
> different frequencies.
> 
> Am I on the right idea with this?
> --
> Send bugs reports to this list.
> To unsubscribe, send email to csound-unsubscribe@lists.bath.ac.uk
> 

Robson Cozendey wrote:

> Hello everyone,
> 
> In the Hans Mikelson instrument for tube distortion in the CSound Book, 90% 
> of the beautiful distortion effect in instr 3013 lies on the line:

Would someone be kind enough to either post this orc to the list
or email it directly to me?

TIA,
Erik
-- 
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  Erik de Castro Lopo
+-----------------------------------------------------------+
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