Xpantastic!

From: analogholic
Subject: [xpantastic] Faster envelopes on Matrix 12/Xpander - Conversation with one of the designers
To: xpantastic@yahoogroups.com
Date: Tuesday, September 9, 2008, 4:52 AM

Hi everyone,

When I read the "percussive like patches"-thread, I was reminded that
I while ago (when the Matrix 12 was my only analog synth) that I (as
many others) was a bit frustrated with the M12´s slow enevelopes.

SoI wrote an email to one of the creators of this beast(Michel Doidic)
and asked what could be done. Here is our conversation:

"Mr Ryle, Mr Doidic, first off I want to thank you for being part of
designing (among other things) the fantastic Oberheim Matrix 12.
I have the incredible luck to have found one (Matrix 12) for sale in
Sweden. Although this is very "off topic", I would be incredibly
grateful and happy if you guys could try (who else could?) answer the
following question: Do you think it would be possible in some way to
modify the envelopes of the Matrix 12 to be faster ?
I know they are software envelopes, but today there are a lot of
softEnvs that are snappy, also on at least two analog synths which
have softwareEnvs (one is Studio Electronics Se-1/x) where if you
changed a resistor on the motherboard, the software envelopes became
dramatically faster and snappier, almost at Minimoog speed.
Could it be enough to change resistors in the right place, or would
it be necesarry to recode/reprogram the whole software for the Matrix
12? I know this a hard question, but a solution,if possible, would
mean that a fantastic synth would become the greatest of them all
IMHO.
I thank you once again and send you my best
regards Attila"

His answer:

"Hi Attila, To do the job right would be very difficult because, as
you noticed, the envelopes are generated by the code of the 6809
microprocessor. Short of using a faster 6809 (assuming that you could
get one) and modifying the code there is not much which can be done.
The Matrix 6 and 12 were designed about 25 years ago, and
microprocessors where a lot slower back then. There is still a bit of
hope however. The fastest time for the envelopes is about 2
milliseconds.
This could be reduce to 1 ms by changing RX51 for the VCA (where X
will be 3, 4, 5, 6 or 7 according to which of the six voice it
controls on each of the two voice boards) from 18K to 9.1K.
The next fastest time is set by the microprocessor and an analog
smoothing filter on the voltage control circuit (= Sample and Hold).
This time is set not only by the software but also by a resistor RX14
on each of the main voice PCB for the VCA control and by RX10 for the
VCF frequency control.
You may want to try reducing these resistors from their original 1 M
Ohm value to let say 500K Ohm. This will reduce that time from about
7 ms to about 3.5 ms. The draw back however is that you may get more
discontinuity in the shape of the modulation.
The next fastest times however will still be determined by the 6809
software and that will not change. Give it a try on one of the voice
and see if that goes toward what you want.
Hope that this helps a bit. Michel Doidic Line 6 CTO"

OK guys, what do you think?

I changed a resistor in my SE-1, and it become snappier (not
fantastic, but better)
Also, the Chroma has a reputaion of very slow envelopes, but same
thing there, if you remove a resistor or change it to a lower value,
envelopes supposedly become faster.

I would even go so far to check out the possibilities of putting in a
faster processor and find someone to recode the software.

Brainstorming please begin :)