MOTM

Sorry! This one is really long!

In a message dated 2/24/99 1:11:32 PM, "Dave Bradley" <daveb@...> wrote:

>C'mon, shoot off yer big mouth 

Boy! When you sweet talk me like that, I mean how can I resist!

The Serge TKB is essentially two modules, a sequencer, and a non-standard
touch sensitive keyboard.

The sequencer is 16 (stages) X 4 (rows). Each of the 4 CV outputs (A B C D)
will provide a continuous 0-5V. Each stage has a 5v pulse out. The inputs are
1) clock, 2) hold, 3) up/down, 4) reset (which will either set the next stage
to the last reset stage, the last key selected from the touch pads, or a
random stage if the random input is also high), 5) random (which only works
with the reset high). There is also a vertical clock and a vertical (A B C D)
CV output. This 4 stage sequencer only works in one direction and is useful
for arpeggios, or to extend the length of the sequence from 16 to 64  for
example.

The Touch Keyboard is 16 touch sensitive pads. It has a switch which locks the
sequencer to the key pads which defeats the sequencer when a key is pressed
and forces a stage select, or in the OFF position selects the last pad touched
when the RESET input goes high. The keyboard provides a (5V) gate out, a
keyboard CV out and a touch pressure CV output. The pressure output provides a
0-5V continuous voltage determined by the "pressure" applied to the pads. I
find this output best suited for timbre modulation or filter CV (Q or freq),
or VCA amplitude control, though I have used it with syncing oscillators and
VC dividers for interesting pitch control involving VCOs; it's way too touchy
for direct pitch control in any predictable way. 

The keyboard CV output is 0V to 5V in equal steps for each of the 16 stages.
As such it can be tuned to provide a root, a "third (somewhere between a minor
and major)", a "sixth (again between a major and minor)", followed by an
octave. This pattern repeats over the five octave range. I found this a bit
limiting at first until I touched two pads simultaneously and found that it
could then provide voltages which would generate many (maybe all) of the
chromatic pitches, and many micro tonal pitches. Clearly, some ratio of the
scanning clock frequency, and the distance between the pads touched produces
an intermediate voltage (and yes you can hear some sub octaves of the clock at
the higher frequencies).

I haven't probed around inside to get an idea of how it works, and Serge
didn't provide schematics with the kits (the boards came pre-assembled) I
assume to prevent people (like us) from copying his stuff. I'm sure Paul could
figure it out and I do hope he will provide alternate controllers as time goes
on; for example:
1) a ribbon controller,
2) a TKB (without the sequencer) that has pressure sensitivity, and 60 small
pads for the full chromatic scale over the 5 octave range.

I do realize that Paul has to offer modules that (normal) people would want to
buy, So the more exotic ones that I might enjoy could have a very limited
appeal (although I believe that there has been enough interest in a ribbon
controller that it would find a fervent audience if not a very large one).


Just the other day I was on the PAIA site. That old
>touchpad drum thingie that they used to sell has a circuit published online
>that shows how you would do the velocity and pressure sensitive touchpads
>part of a TKB. 

There was a thread about this on the DIY list about 6-8 months ago. There were
schematics on at the synthfool site by Arpard Barnes (sp? a non de plume for
Serge T.) that show the touch pads (without the pressure CV out) and the
sequencer (as a programmer, without the clock). I'm quite sure that Serge used
different methods than John S.

I just don't know enough about all the other things a TKB can
>do. So give us a report when you get the time!

I hope I answered any thing you wanted to know.

>BTW, is it just my imagination, or do you have to be careful saying the word
>"filter" around Paul? He's likely to go berserk and start churning out new
>filter modules at lightspeed<VBG>!

Let me try: FILTER; state variable with VC Q, and VC slope. Hey! It's worth a
try!

Synth Peon
JB
Did anyone else notice that as we approach the first anniversary of MOTM there
will be a complete synth voice and several non-standard modules available?
This thing is going really well!