[PolyModular]

[Harry Bissell]

Hi. I just thought I'd piss off everyone on the list, starting with JH.

The first thing to do would be to define a module STANDARD (remember that
fiasco...)

We might (optional) want to agree on some kind of form factor. If the pots are
pcb mounted, this is vital. I'd like to suggest that we mount the DIN jacks on
the PCB (there are great inexpensive PCB mount jacks) and leave the pots off
board.

I think there might be fewer VCA functions than you think. There are lots of
good voltage controlled (name of function here)... like VC-ASDR... They would
only need standard pots... only the output level needs a VCA.

And lets not cheat ourselves... If one transistor serves the function great,
but there's no reason to skimp esp. on the filters. Do not fear lots of
components on the PCB... that is what PCB designers do for a living. Real
estate should be no problem... It is likely that PTH 2 sided boards would be
required and that might let out people making the boards themselves. I'd vote
for buying the PCB's en-masse, and maybe some other critical components.

Personal preference (no need to do the merits post again, I read them all) for
V/oct. If we really use a modular format, maybe I'll make a
pentaexpoconvertermodule. V/oct was always the de-facto standard, and V/hz the
orphan cousin...

I like the idea of six voices... Maybe someday, someone will make a guitar to
CV converter that really works... like in REAL TIME (not 30mS into the
past...). And it would let us use the word "HEX" instead of the clumsy "Penta"
 Hex VCO, HEX VCF.....

A lot of commercially available MIDI cables are "MIDI-SYNC" cables that have
all five pins. We should be careful about the shields though... MIDI usually
grounds only one end of the shield. Crosstalk will be a bit of a problem for
audio signals (like VCO pulse etc...)

Some of the VC select schemes for waveforms would be nice...

The DIY-PCB group might want to play... There are some good panel layout ideas
there...

Juergen H: maybe you could think a bit about what some signal STANDARDS (oh
yeah I forgot I said I'd not use the "S" word again) might be. I mean
suggested (oops thats "S" too...) recommended?? Anyway... voltage levels for
Audio signal and CV. I know the fun of a modular is to plug anything into
anything... but a two transistor VCA is not going to handle 10V signals
without being unhappy. I'm kind of wide open on this one... I like 10V
signals, but some folk like 5V, etc. 

If we had signal standards, then we might form design teams.... We have a wide
rande of talent in this group, but I know I'd feel more comfortable with ENV
GENs and LFOs than 5 or 10 VCO that must all track...

I just read a "get a life... get a micro" post. I don't think they are a
necessity but I could be convinced... The problem is the lack of support a lot
of us have for micros... Maybe someone wants to head a mirco interface team
and work with the analog folk on some standards for handshaking. Maybe a
system that just reads the analog voltages and can reproduce them at will. But
(just being playful here) I dont want to build a modular DX7 either. The
analog system has infinite resolution... 7 bits won't get it. The keyboard is
a good place for a micro....

Well I bet I've pissed of everybody enough by now. When the dust settles we
should have a real good picture of what this machine might be... Did I say
"when"?  I meant "IF".   ;-) Harry (V/oct) Bissell


jh <jhaible at primus-online.de> wrote:
No, I have not startet such a project, but for some reason
it starts "knocking at the door of my brain" once again.

I came up with this idea a few years ago, but I didn't 
feel comfortable enough with it back then. But maybe
I do now.

The outline of such a system, as I see it from today's point
of view, would be like this:

(1)

5-Voice polyphonic. What is enough for a Prophet 5 should
be enough for a PolyModular, too.

(2)

No 1/4" jacks for connections, obviously. I still think it
could be done with these old "DIN" HiFi cables (same
connectors as Midi). They are cheap and you can buy
them in various lengths - no soldering of cables required.
They are sturdy enough for studio use at least. They
have 5 pins for 5 voices, plus a shield.

(3)

Every potentiometer in a "normal" modular would have to be 
replaced with 5 VCAs. This used to be frightening for me
back then, but it isn't any longer. We can learn a lot from
these Korg PS synths. What they were able to do with full
polyphony should be possible for a 5-voice stem, too.
Yes, 3-transistor filters, and single transitors or even diodes
for certain VCA functions. And EMS used a single FET 
for the VC resonance of their diode ladder filter...

(4) 

Mixed linear / exponential VCOs. Another thing to learn
from Korg, MS series this time. Make the keyboard CV
linear (V/Hz), and do the exponential modulations with
a non-tempco exponential multiplier. And I don't see any
reason why the Emu / Oberheim keyboard circuit shouldn't
work with exponential D/A conversion as well !
No Autotune required then. What is possible in a CS-60 ...
you get the idea (;->)

I really start feeling excited. It will be possible, and it will not
be much more expensive than a monophonic system.
I probably cannot build such a thing all alone. With everything
in a module x5 pcb's would be crucial - no veroboard here.
But do a *small* circuit once, and just copy and paste.

No idea if I get such a project off the ground, but the 
tempting thought is that the *really* expensive things of
a modular, i.e. front panels and potentiometers, are the
same as in a monophonic system.

So the question is: Are more people interested ?
I think I could manage to come up with the *circuits* for all the
basic modules within one year or so. Is there someone who
could do the pcb part ? (Of course there is the possibility
for everybody to add special modules, but 

Once again: at the moment it is no more than checking an idea.
I don't know if I ever find the time. But then again, I can
hardly stop building (addiction ....), but such a system
would possibly be the only thing I'm really interested in at the
moment.

What do you think ?

JH.


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