MOTM

Following up my recent mail, here it is online:

I finally started that insane project of building a polyphonic
(4-voice) Modular System.
The first Module is finished, an Interface Module to use the
Yamaha CS-50 as a keyboard controller.

If you want to take a look, schemos and front panel
graphics are here:

http://home.debitel.net/user/jhaible/additional_schemos.html

At the moment there is just that, the interface. And a lot of ideas
in my head. But I feel that actually building the first module was
like crossing a boarder - no more easy going back now. (;->)

Meanwhile, it's good to play the Minimoog clone from the
CS-50 keyboard, doubling the bass note.

And sweeping the MOTM Triple Resonant Filter with the
CS-50's aftertouch !

JH.



-----Urspr\ufffdngliche Nachricht-----
Von: jh. <jhaible@...>
An: <motm@egroups.com>
Gesendet: Sonntag, 8. Oktober 2000 22:10
Betreff: Re: [motm] Yamaha CS-5/10/15 as MOTM controller


>
> > I think this came up a while back; do the old Yamaha CS mono synths have
> > normal 1v/octave CV outputs and regular gate or trigger outs that are
> > compatible with MOTM?
>
> I don't know if the CS monos had a V/Oct output (I doubt it).
> But ...
>
> I am currently expanding my CS-50 to be the center of a 4-voice polyphonic
> Modular synth. While the polyphonic CVs will be V/Hz (as inside the
CS-50),
> it will have two extra V/Oct outputs for driving monophonic V/Oct gear
> (such as MOTM) as well. What you need is (basically) a logarithmic
converter
> which is a standard building block more or less, but to make it useful for
> musical purposes, I have added some features like octave range switches,
> single trigger / multi trigger logic etc.
> And I'm also bringing out some of the CS-50 internal modulation signals
> (PWM LFO, "SUB" LFO, and Ring Mod OSC) with the interface as well.
> It's almost finished, and I hope I'll be able to publish the schematics in
a

> few weeks. i don't know how close the monophonic CS synths are to the
> CS-50, but I assume there are similarities.
>
> JH.
>
>
>
>

--- In motm@egroups.com, jhaible@t... wrote:
> Following up my recent mail, here it is online:
> 
> I finally started that insane project of building a polyphonic
> (4-voice) Modular System.
> The first Module is finished, an Interface Module to use the
> Yamaha CS-50 as a keyboard controller.

How does this fit with the JH-4, your other polysynth project. I 
thought you were doing something else for the poly kbd controller.

Dave

> How does this fit with the JH-4, your other polysynth project. I
> thought you were doing something else for the poly kbd controller.

The JH-4 was intended to become something like a Oberheim 4-Voice,
i.e. 4 separate voice modules and one keyboard. I even choose the size
of one voice module to be exactly one quarter of a 5-octave keyboard's
width ...
The idea behind the JH-4 was playing 4 different sounds with various
voice assign modes. And that's what I'm using it for. The (still single)
JH-4 voice module and the Minimoog clone are normally controlled
from that Oberheim-clone keyboard, so it's normally a 2-Voice, but
I also have created two additional voices from 4 VCOs etc. of my
"ordinary" Modular, the JH-3.
Now there is one thing I do not like, that's doing the same thing more than
once unless there is enough pressure - so I never got  to build 3 more JH-4
modules. Some parts of the JH-4 are not as I would build them today,
mainly the OTA-based and offset ridden VC envelopes. If I had to do
it again, I'd use the same offset free VCA core which is also part of the
MOTM VCLAG. And The JH-4 module had soft sync (interlock) problems.
I've cured that with cutting traces and adding wires, but then I don't feel
like
doing a redesign just for fun (or for the lack of fun).
This is not to put that module down - I still think it's one of the better
instruments
I've buit. And I heard a silent voice telling me that the best part of it
might
become a MOTM module (;->). (Don't ask - I won't tell before Paul does.)

Now that new PolyModular is something different. 4 Voices which are always
set
to the same sound, just like a ordinary Modular, but playable with 4 voice
polyphony. I just can't leave that domain to Nord Modular and the like,
could I ? (;->)
I think the most expensive, and the most important part of a good Modular
are the mechanical parts anyway (this has always been my argument to support
high
quality synths like MOTM and to detest budget stull like D.). So, if I spent
a
decent sum on front panels and switches and pots, I can as well build
quadruple
electronics. And these electronics needing some pcb space is enough pressure
to build large ergonomic front panels as well.

JH.

--- In motm@egroups.com, jhaible@t... wrote:
> Now that new PolyModular is something different. 4 Voices which are 
> always set to the same sound, just like a ordinary Modular, but 
> playable with 4 voice polyphony. 

So a single set of controls for multiple voices, ala P5 and others? 
Do you put VCAs everywhere in each voice to control signal and CV 
levels, or do you use something different like the Xicor digital pots?

Moe

> So a single set of controls for multiple voices, ala P5 and others?
> Do you put VCAs everywhere in each voice to control signal and CV
> levels, or do you use something different like the Xicor digital pots?

VCAs will be on each output. Depending on the module this can be
a full fledged VCA or something less involved. For scaling the output
of an unipolar envelope 5 transistors (+opamps) might be enough.

JH.

--- In motm@egroups.com, jhaible@t... wrote:

> VCAs will be on each output. Depending on the module this can be
> a full fledged VCA or something less involved. For scaling the 
output
> of an unipolar envelope 5 transistors (+opamps) might be enough.
> 

I'm still struggling with the concept. Is it a fixed architecture 
voice? If so, how do you control VCO volumes into the filter, poly 
mod amounts, resonance, etc - all those things in a P5 voice which 
required a separate VCA?

Or is it something wilder, with physical patch cords representing 
somehow identical patching in 4 sets of electronics? How in the heck 
would you pull that off without an elaborate electronic switching 
matrix?

I'm so curious because I designed many poly synths in the old days of 
SSM chips, but still never built any because of the sheer amount of 
hardware required.

Moe

> I'm still struggling with the concept. Is it a fixed architecture
> voice? If so, how do you control VCO volumes into the filter, poly
> mod amounts, resonance, etc - all those things in a P5 voice which
> required a separate VCA?

Just an ordinary Modular, but 4 parallel inputs and 4 parallel outputs
instead of single ones.
For instance a VCF module will be not one VCF circuit, but 4 VCF
circuits, with individual inputs, outputs and modulation signals,
but with shared manual controls. So, one knob for cutoff frequency
will set the initial cutoff for all 4 filters, but each filter will get it's
own envelope, keyboard tracking and so on.
Where you usually would have a pot to scale an input or output,
I don't use a quad pot, but 4 VCAs and a single pot.
I'm putting these VCAs at the output of the modules, so every
modulation depth, filter overdrive etc is controlled by the level
of the *sending* module; inputs have fixed sensitivity. (This
concept works nicely in the VCS3 for instance.)
As I have a VCA at the output of every module anyway, I won't just
use it to emulate a quad pot, but I can sum individual CVs to individual
VCAs as well, so I get a complete VCA with every module for free.
Take 2 VCOs routed into a VCF as an example: The built-in VCA at
the VCO output can just be used to manually set the mix of both VCOs
and the filter overdrive. But it can also be used for dynamically mixing
the VCOs with an extra envelope. Like: 1st VCO goes to VCF with
manually set amount, second VCO has manual output level set to zero
and is controlled by a short AD envelope to be active for a shor time
only.
So, as long as there is only manual level control, the 4 VCAs per module
are surely an overhead, but as soon as I patch dynamic mixing etc. the
concept starts to become interesting.

> Or is it something wilder, with physical patch cords representing
> somehow identical patching in 4 sets of electronics? How in the heck
> would you pull that off without an elaborate electronic switching
> matrix?

I'm using 5-pin "Midi" cables. Not the worlds best connectors, but
available and affordable. It will be clear when you'll see a photo;
on the front panel layout you just see the 16mm holes and two tiny 3mm
fixing holes for each 5-pin jack.

> I'm so curious because I designed many poly synths in the old days of
> SSM chips, but still never built any because of the sheer amount of
> hardware required.

Yes, the wire harness inside the first module is quite impressive. I've
made a detailed plan of a mechanical concept before I started, and
apparently ot works. For the interface module I have 2 strong metal
braces attached to the front panel (19" 3U) which hold a rectangular
wooden frame. The frame is made of 15mm x 15mm wood, and it spans
an area that holds 4 eurocards (160 x 100 mm) such that the bottom of
the pcbs (veroboard, actually) is acessible from the bottom for repair
and mods, even when the whole thing is assembled. Wiring to front
panel comonents is done from the upper side of the pcbs, with ribbon
cable for unsensitive signals, and 4-wire shielded cable for sensitive
signals. The wires are soldered at the front panel components, and there
are tiny pcb connectors on the veroboard end.
Every module will probably get its own tiny pcb mount toroidal
transformer, so I don't expect grounding problems and everything is
self contained.

JH.

----- Original Message ----- 

From: <jhaible@...>
Every module will probably get its own tiny pcb mount toroidal
transformer, so I don't expect grounding problems and everything is
self contained.
---------

What transformers have you found suitable for this purpose?
Larry Hendry

> What transformers have you found suitable for this purpose?
> Larry Hendry

In the Interface module I've used some toroidal I had left over,
which I bought from Farnell once.
But when I'll buy more transformers, I'll chose these blue ones
that RS Components sell. They are looking a bit like these
flat PCB mount transformers (that have such an ugly stray field),
but as these are real toroidal ones, encapsulated in plastic,
no stray field problems here. They are not cheap (as all toroidals),
but they are tiny and excellent to use on board.

JH.