[sdiy] pwming a tog

[Adrian Corston]

You can construct fixed lower octave PWM signals to some degree, by
ORing the signals from multiple octaves above.

f0=10101010 OR f1=11001100 => f2=11101110 (ie. f2 two octaves below
f0, with a 3:1 PWM ratio)

Similarly AND gives you a 1:3 PWM ratio.

Obviously your pitch width options are quite limited using this
approach and it's not really what you were looking for.  But it might
be interesting nevertheless :)  I'm pretty sure I've seen this
technique used in a vintage organ circuit somewhere.  I'm equally
sure it would require a whole bunch of extra circuitry....

Cheers,
A.

----- Original Message -----
From:
 "Dave Garfield" <daveogarf at yahoo.com>

To:
"Tom Wiltshire" <tom at electricdruid.net>, "Mike HEQX" <mike at heqx.com>
Cc:
"Synth DIY" <synth-diy at synth-diy.org>
Sent:
Tue, 19 Sep 2017 23:49:10 +0000 (UTC)
Subject:
Re: [sdiy] pwming a tog

Hi, all
While it doesn't do PWM, an English company named FlatKeys produces a
Top Octave Generator replacement for the classic synths and organs
which use a 50240 TOG.  This one isn't just a divider; it generates
12 separate top octave waves which are in tune, unlike the originals'
approximations.
It will also do vibrato, as it has a master clock. It can switch
octaves if desired, or transpose keys.  
The price is £52.80.
I haven't tried one out, but have been meaning to for a long time. 
If anyone else out there has, I'd love to hear about it - warts and
all.  Maybe it will work for you, or someone else out there.
FK50240 MK50240 [1] 
I am NOT affiliated with FlatKeys in any way, shape, form or manner. 
Just thought that this might be a good solution for replacing scarce
top octave divider chips.

 [2]

FK50240 MK50240

    On Tuesday, September 19, 2017 5:32 PM, Tom Wiltshire
<tom at electricdruid.net> wrote:

Because the standard TOG is based on dividers, you can’t add PWM.
Run any width pulse wave through a flip-flop and the output's a
square, after all.

That said, there were some TOGs the produced 33% pulse waves rather
than squares (not sure exactly what the internals were to do that) but
there were none that offered PWM.

If you had twelve ramp oscillators for the top-octave, you could
arrange ramp+squares to give you ramps at various divided octaves, and
then use those ramps to produce PWM, but it’d be a lot of circuitry,
and it’d probably get a bit sensitive. Have a search for
“sub-octave ramp wave” to get the basic idea.

HTH,
Tom

==================
      Electric Druid
Synth & Stompbox DIY
==================

> On 20 Sep 2017, at 00:06, Mike HEQX <mike at heqx.com [3]> wrote:
> 
> I wanted to do something with a TOG and I was hoping I could add PWM
to it. Not sure if you can PWM the master clock though, but that's
what I want to try. After all you pitch bend it that way.
> 
> I not does that mean 12 pwm on the output of the tog?
> 
> 
> thoughts?
> 
> 
> Mike
> 
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org [4]
> http://synth-diy.org/mailman/listinfo/synth-diy [5]

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Links:
------
[1] http://www.flatkeys.co.uk/MK50240.html
[2] http://www.flatkeys.co.uk/MK50240.html
[3] mailto:mike at heqx.com
[4] mailto:Synth-diy at synth-diy.org
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