MOTM

> The clicks are because you are trying to run about 100Hz sampled DC as a
> control
> voltage to a VCA. You cannot do this.
>
> A S&H is used *mainly* for controlling a VCO. Try this patch:
>
> S&H Out >> 1V/Oct in on a VCO (or on a VCF)
>
> This will randomly move the VCO/VCF's center frequency to a different point
> with each samle pulse.
>
> The 'classic' S&H patch is to feed a saw or triangle into the S&H and use
> the output into a VCO.
> This will make arpeggiated "runs" and you can vary the 'tune' it plays by
> ever-so-slightly
> changing the input frequency. Low frequency input waves  (<20Hz) are best
> for this.
>
> If you want to use the S&H output into a VCA control input, you will have to
> place a slew limiter
> on the S&H output first (a VC limiter is in design now). Otherwise, the vca
> "pops" which is what you
> are hearing.
>
> Paul S.
>

Hi everyone,
  I've been getting annoying S&H pops on my MOTM-100 also. This is very
noticeable when patched to the VCF. At first I thought this was part of the
"badness" of the '420 design. But I get audible clicks on my Minimoog filter as
well. So I investigated further. Tried two other type S&H units but no popping.
There had to be an explanition. So I tried running the '100 through the Mini
keyboard circuit, instead of straight to the VCF, and the popping went away.
Interesting! Apparently the '100 changes voltage so fast there is a click when
routed directly to the VCF or VCA. The keyboard circuit seemed to smooth the
transition between voltages ever so slightly and kind of morphed the resulting
output wave. No more pops or metronome like clicking.
Here is a sample wave of the S&H filter sound first through the Mini keyboard
circuit(no pooping), then straight to the VCF (loud popping).

http://www.geocities.com/SunsetStrip/Frontrow/4877/sh02.wav

If you look at this wav in Sound Forge and Magnify 1:1 you can see the smooth
transition between samples in the first part. The changes have nice rounded
edges
between samples. On the second part the changes are very abrupt. Harsh straight
transitions between samples causing pops.

OK, so the circuit needs some kind of lag to be musically useful. But how.
I'm not a tech so I tried a few things by "ear". I came up with a 1uF 25v.
electrolytic across the output jack. Negative connected to ground and
positive to the output. Seemed to work? I substituted larger values but
got an audible lag, like a "wah" on the filter or glide on VCO. I didn't have
any smaller values, but 1uF seems an inaudible amount of lag. I also
tried loading up the output with the 1uF installed, ran to the VCA,VCO,
2 filters simultaneously to see if I got more lag, but seemed OK.
 Can you help here Paul? Should I have a 741 follower after this. Is there a
better way? I don't want to use a full blown lag module for this simple task.
Could put a switch on the '100 panel to put it in and out of the circuit. A
"soft/hard" switch? Or is there something wrong with my '100?  Didn't anyone
else notice this?

 Anyhow the S&H filter sound is one of my favorites. And this S&H really
kicks ass when running other instruments through the filters.
Here's a small zipped MP3 of last weeks jam session with the popping
S&H filter sound. Next week no popping!

http://www.geocities.com/SunsetStrip/Frontrow/4877/clickjam.zip