Something new(ish)? (Re: 1970's again? (was Re: [sdiy] pro EQs))

[Bill Felton]

There's also a very nice ElectroNotes circuit that, IIRC, had 
back-to-back diodes in the feedback path of an op-amp, (output being 
then basically center-clipped), then amplifying and adding the normal 
(or inverted) center-clipped signal back in to the original.  At full 
effect on triangle wave input, this gave frequency tripling.  But the 
intermediate stages from tri (or other continuously varying, ie, no 
pulse wave inputs allowed) to the 'full effect' setting gave a sound 
transform that was rather the inverse of typical synth filtering -- you 
went from a low-harmonic to high(er)-harmonic content sound, under vc 
of center-clipping amount and mix.  Since this needed no exp. 
converters to track, it was significantly cheaper than a filter 
circuit, gave an effect similar to, but different from, the 
time-variation in timbre from a filter, and thus played a comparable 
role in the patching ecology.
(I've got two I built and love them; Cynthia is panelling them for me, 
along with my EN MultiPhase Waveform animator.  )
cheers,
Bill

On Dec 31, 2004, at 8:35 AM, John Loffink wrote:

> Look here:
>
> http://www.oldcrows.net/~patchell/synthmodules/shaper.html
>
> and here:
>
> http://www.wavemakers-synth.com/motm/dws.html
>
> for examples of diode waveform shapers.
>
> I find my shaper useful for adding gradual degrees of distortion to
> waveforms, or making "composite" tones by modulating with waves from
> multiple VCOs or VCFs.
>
> You are correct that these circuits originated with analog computing, 
> yet I
> have never seen an implementation in "classic" (i.e., Moog, Buchla, 
> Serge,
> Emu, etc.) modular synthesizer format.
>
> John Loffink
> The Microtonal Synthesis Web Site
> http://www.microtonal-synthesis.com
> The Wavemakers Synthesizer Web Site
> http://www.wavemakers-synth.com
>
>
>> -----Original Message-----
>> From: owner-synth-diy at dropmix.xs4all.nl [mailto:owner-synth-
>> diy at dropmix.xs4all.nl] On Behalf Of Anthony Ankrom
>> Sent: Friday, December 31, 2004 8:09 AM
>> To: Paul Maddox; Synth-Diy
>> Subject: Something new(ish)? (Re: 1970's again? (was Re: [sdiy] pro 
>> EQs))
>>
>> I have read about something that I don't think anyone's ever applied 
>> to
>> synth work, but it might be
>> interesting.
>>
>> Just the other day I stumbled across an old article about "non-linear
>> transfer functions". The circuits in the article
>> used very large arrays of "forward biased" diodes in the feedback 
>> loops of
>> op-amps. It said forward biased but
>> the diodes were "pointing" the same way as the op-amps so I would 
>> think
>> this
>> would be reversed biased, but hmm
>> maybe it was because it was in the inverting input?
>>
>> And the arrays seemed to be strings of diodes of varying/increasing 
>> length
>> in parallel. Like the first was one in
>> parallel with a string of two in parallel with a string of three and 
>> so on
>> -
>> with variations on this theme.
>>
>> The aim here was some analog computing application, but isn't that 
>> what
>> analog synths are in a nutshell?
>> They're analog number crunchers with audio user interfaces.
>>
>>
>
>
>
>