MOTM

In response to Dave's observations:

>I finally figured out that I was cranking the input signal (MOTM-300) too
>hot. If I back off the attenuators to 12:00, it sounds sharp and clear with
>cutting resonance. As I crank the signal more, I get some distortion, and
at
>the same time the resonance decreases. There is a gain zone where you can
>get both distortion and high resonance. Increasing the gain beyond that
adds
>more distortion, but overwhelms the resonance. Since Paul mentions on the
>web site that this design has nonconstant Q with gain, I figure that's what
>I'm seeing.


That is correct. This is the #1 "uniqueness" of a MS-20 filter. You can get
all combinations
of resonance/clipping going, as well as a "clean" sound. I use 2 '300s and
set the IN attenuators
on about 6.

>Another tip - the notch setting is most useful either at NO resonance, or
>lots of resonance. At no resonance, you get the swept notch kinda stuff. At
>high resonance, you can add a resonant peak without cutting highs or lows
>like LP or HP modes.
>
>At mid level resonance, however, you are just nullifying the notch and it
>will sound pretty close to having no filter at all.

Exactly correct again. The Notch is really best heard with 2 '420s. Also
sweping
2 Notches makes for some good phaser effects.


*************

On another note:

If you twist the IN pots with a "hot" signal (ie VCO direct output) plugged
in, you
may hear some "grunge noise" that then disappears. This is an artifact of
the
filter "bouncing" as it gets it's level rapidly swept. The pots are NOT
"bad", the filter
is mis-behaving, in a MS-20 way.

Nice to see that '420s are coming alive this weekend.

Paul S.

Thanks to Dave for his observations about good ways to use the 420. I had 
noticed some unpleasant clipping until I reduced the level a bit -- but then 
again, I'm a guitar player: distortion is ALWAYS good init? And I did find I 
get a pretty good clean level around 6 to 8.

And thanks as well for the notch filter tips. On any given filter excluding 
BP, I find myself using LP about %85, HP about %15, and notch the rest of the 
time -- but I'm not saying I don't like notch filters! With two 420s, some 
interesting phase type sounds would be available I'm sure.

I did notice a rather significant pitch drop (maybe a semitone) as Q goes 
from first feedback (at 8) to very saturated (at 10) -- I actually liked this 
though I may move initial feedback to about 9 eventually. I also noticed the 
dirt noise in the pots, I'm glad to hear I didn't fry mine when I soldered 
them in.

This filter is very nice, but when it misbehaves (in an MS20 way) it's even 
better!
John B.

In a message dated 7/3/99 1:34:15 PM, synth1@... writes:

>That is correct. This is the #1 "uniqueness" of a MS-20 filter. You can
>get
>all combinations
>of resonance/clipping going, as well as a "clean" sound. I use 2 '300s
>and
>set the IN attenuators
>on about 6.


>On another note:
>If you twist the IN pots with a "hot" signal (ie VCO direct output) plugged
>in, you
>may hear some "grunge noise" that then disappears. This is an artifact
>of
>the
>filter "bouncing" as it gets it's level rapidly swept. The pots are NOT
>"bad", the filter
>is mis-behaving, in a MS-20 way.