[sdiy] Sweep through waveforms

[Grant Richter]

Now you let the cat out of the bag...

Yes, running the circuit backwards makes a 5.1 panner (or 8.1) it just needs
a joystick interface and a dome function to turn all channels on in the
middle.

In this circuit the slow Vactrol response (35 millisecond decay) is used to
integrate the PWM pulses into a continuous signal. The photo resistive
material can not respond fast enough to the light pulses and integrates
them. Anything over 200 Hz should work as a dither signal. I used 44.1 kHz
just for overkill.

Individual voltage outputs can be had with photo-voltaic pile optoisolators.
The photo-voltaic piles are also slow and will integrate light pulses into a
function, and you then have a voltage output scanner like Jurgen and Jims
designs. But I think I win on parts count (no offense OK, the other circuits
are more precise)

The same principle is used here

http://www.musicsynthesizer.com/DIY/Grant/CVtwister.html

only the channels are summed and then lowpass filtered. In the mixer case,
the slow Vactrols do the filtering for us. R6 can be a 10K to start.

> From: Peter Grenader <petergrenader at mksound.com>
> Date: Sun, 17 Nov 2002 23:49:30 -0700
> To: Grant Richter <grichter at asapnet.net>, elmacaco <elmacaco at optonline.net>,
> patchell <patchell at silcom.com>
> Cc: <synth-diy at dropmix.xs4all.nl>
> Subject: Re: [sdiy] Sweep through waveforms
> 
> 
> I spent an hour or so looking over this when i was first posted, and this
> circuit of Grant's's has about a billion uses that would be extremely
> interesting.  My first synapses were using it as an output select for a
> fixed filter bank  or a frequency divider- t'would be interesting in dot AND
> bar mode.
> 
> The vactrols, being the sluggish beasts that they are, would augement the
> 3914's decoding and give you some interesting morphing effects.
> 
> And imagine if the same signal was put into each channel. If you didn't
> incorporate the summer but  had separate outs for each channel and   slowed
> down the vactrol response time further than it is aby design, me thinks it
> has the makings of a great multichannel panner.
> 
> I never thought of a multiwaveform selecter Grant suggests (ala the NTO),
> but yeah, this would be sweet as well.
> 
> P
> 
> 
> 
> Grant Richter wrote:
> 
>> 
>> El cheapo crossfade scanner.
>> 
>> Not precise, but cheap and simple to build.
>> 
>> http://www.musicsynthesizer.com/Corpse/VCEOM.html
>> 
>> Bargraph chip is dithered to PWM drive optocouplers, so you can blend,
>> crossfade or switch depending on dither amplitude.
>> 
>>> From: elmacaco <elmacaco at optonline.net>
>>> Date: Mon, 18 Nov 2002 19:54:07 -0500
>>> To: patchell <patchell at silcom.com>
>>> Cc: synth-diy at dropmix.xs4all.nl
>>> Subject: Re: [sdiy] Sweep through waveforms
>>> 
>>> ah!  thanks.  scanner makes sense as a name.  beats quad crossfader ;)
>>> 
>>> somewhat what I expected.
>>> 
>>> off to study that schem.
>>> 
>>> thanks.
>>> 
>>> ed
>>> ----- Original Message -----
>>> From: "patchell" <patchell at silcom.com>
>>> To: "elmacaco" <elmacaco at optonline.net>
>>> Cc: "Dominic Tarr" <dmt10 at waikato.ac.nz>; <synth-diy at dropmix.xs4all.nl>
>>> Sent: Sunday, November 17, 2002 5:55 PM
>>> Subject: Re: [sdiy] Sweep through waveforms
>>> 
>>> 
>>>> Or maybe the Don Tillman Interpolating scanner
>>>> 
>>>> http://www.till.com/articles/scanner/index.html#Ref SSM-2024
>>>> 
>>>> 
>>>> elmacaco wrote:
>>>> 
>>>>> tri-saw-square-narrow pulse.
>>>>> 
>>>>> Ok, I guess that could count as three.  It still puzzles me.  I know a
>>> few
>>>>> older synths did this too. just curious about how.
>>>>> 
>>>>> Ed
>>>>> ----- Original Message -----
>>>>> From: "Dominic Tarr" <dmt10 at waikato.ac.nz>
>>>>> To: <synth-diy at dropmix.xs4all.nl>
>>>>> Sent: Sunday, November 17, 2002 4:33 PM
>>>>> Subject: RE: [sdiy] Sweep through waveforms
>>>>> 
>>>>>> sorry to clog your mail boxes with stupid questions but which 4
>>> waveforms
>>>>> does it sweet through?
>>>> 
>>>> --
>>>> -Jim
>>>> ------------------------------------------------
>>>> * Visit:http://www.silcom.com/~patchell/
>>>> *-----------------------------------------------
>>>> *I'm sure glad Merry Christmas comes just once a year
>>>> * -Yogi Yorgensen
>>>> ------------------------------------------------
>>>> 
>>>> 
>>> 
>>> 
>> 
>> 
> 
> 
>