PWM on complex audio signals

[Happy Harry]

Those "Old Timers" may remember an article from sometime in
(if I remember ok) 1970 in Popular Electronics called
"Optimum Fuzz Adapter" by then-newbie... Craig Anderton. It was
a 741 based "schmitt trigger" design. It had a control that would
give "pulse width" but only on a sustained sound like a keyboard.
It had almost no effect on guitar.

I built one... It sucked (IMHO) as advertised. It promised a
"much fuzzier sound" and delivered... and a "rather abrupt decay"
which it also delivered. The decay was the big problem.

I'll see if I still have the schematic somewhere. It was very simple.
I'm naturally suspicious now of similar designs....  ;^)

H^) harry


>From: Magnus Danielson <cfmd at swipnet.se>
>To: don at till.com
>CC: DCMagnuson at aol.com, synth-diy at node12b53.a2000.nl
>Subject: Re: PWM on complex audio signals
>Date: Tue, 02 Jan 2001 22:20:39 +0100
>
>From: Don Tillman <don at till.com>
>Subject: Re: PWM on complex audio signals
>Date: Tue, 2 Jan 2001 10:14:53 -0800 (PST)
>
> >    From: DCMagnuson at aol.com
> >    Date: Tue, 2 Jan 2001 10:02:50 EST
> >
> >    I came across a circuit for adding PWM distortion to a guitar
> >    signal.  The schematic is located at:
> >    http://www.cs.ucl.ac.uk/students/M.Rogers/pwm.html
> >
> > Wow, this is a really bad design.  First off, the input impedance is
> > about 1/100th of what you need for an electric guitar.
>
>Ouch!
>
> > Clipping from the first stage can shoot back out the input and
> > disturb any other devices connected in parallel.
>
>OUCH!
>
> > Schmitt trigger fuzz generally doesn't work on an electric guitar as
> > the signal cuts off abruptly when the player least wants it to.
>
>Not good.
>
> > And Baxendall tone controls just don't sound good with guitar.
>
>Huummmm!!!??!?!!?
>
>There are many reasons not to like Baxendall's tone controls, but I
>would please ask you to elaborate some on this topic. I'd also love to
>hear some comments on what you would use instead and why.
>
>I personally could do with a refreshment on the discussion...
>
>Cheers,
>Magnus - not playing guitar...
>

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