[sdiy] Matrix patch panels

Tue Jan 6 00:11:33 CET 2009

Hallo David!

It is no problem to put more of them in a matrix.
We used I think 8 MT8816 on a PCB in the company I am working for.
For this we used the PLCC44 parts as the whole circuit had to fit on a eurocard sized PCB (160x100mm).

Ciao
Peter

http://www.ullrich.at.tt
________________________________________
Von: David G. Dixon [dixon at interchange.ubc.ca]
Gesendet: Montag, 05. Jänner 2009 23:52
An: Ullrich Peter; 'Synth DIY'
Betreff: RE: [sdiy] Matrix patch panels

Thanks, Peter!  Very cool.  I suppose it wouldn't be that hard to put two or
more of these together into a super-matrix?

David G. Dixon
Professor
Department of Materials Engineering
University of British Columbia
309-6350 Stores Road
Vancouver, B.C.  V6T 1Z4
Canada

Tel 1-604-822-3679
Fax 1-604-822-3619

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-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Ullrich Peter
Sent: Monday, January 05, 2009 10:21 AM
To: 'Synth DIY'
Subject: Re: [sdiy] Matrix patch panels

Hi!

Instead of using 4066 as matrix connections that take quite a lot of board
space you could think of using
analog matrix circuits like the MT8816, MT8804 from Mitel (now Zarlink) or
similar.

http://www.unisystem.pl/ea/uploads/produkty/916/MT8816.pdf  (8x16 matrix)

Depending on the surrounding circuit you can use them as switches for
selections of modulators or even
in mixing circuits for combining modulation signals.
The have a nice microcontroller interface that is easy to progam.

They can also be used for switching video signals!

Remark: Just take care of the addressing table when programming this part.
Two or three address lines are
swapped. I changed these address lines in my schematics symbol to have a
proper addressing scheme.

I used the MT8816 in a universal MIDI interface for synthesizers where 4 of
these chips sit in parallel to the keyboard matrix.
Of course I had to add the decoupling diodes. This is of course not the
cheapest MIDI interface but you do not have to measure the details
of how the matrix is scanned and simulate the keys at the right moments. I
just switch the correct matrix connections and the synthesizer
circuit scans the keyboard and the parallel matrix as it used to do it
before...

Ciao
Peter

http://www.ullrich.at.tt

________________________________________
Von: synth-diy-bounces at dropmix.xs4all.nl
[synth-diy-bounces at dropmix.xs4all.nl] im Auftrag von David G. Dixon
[dixon at interchange.ubc.ca]
Gesendet: Montag, 05. Jänner 2009 18:55
An: 'Michael Bechard'; 'Synth DIY'
Betreff: RE: [sdiy] Matrix patch panels

Hello Michael,

Very interesting project!  I wish you all the best.

Like you, I'm also pretty new to the synth DIY game.  Also, I'm thinking of
something similar, but I'd like to avoid jacks and cables altogether by
hardwiring every possible CV and signal in a switch matrix using LED-backlit
tactile MO pushbuttons, flip-flops and 4066 analog switches to keep down the
hardware cost and to avoid patch cables.  With a bit of extra work, one
should be able to arrange patch memory on such a beast as well.  One could
also program the patches simply by feeding binary words to each row of
flip-flops in the matrix, or randomize them by feeding digital noise to the
flip-flops, which could result in some cool effects (or garbage, who
knows?).  That still doesn't take care of attenuation issues, but it would
at least look cool and be fun and easy to use.  Perhaps each button could be
associated with a little tiny pot on a separate little pot matrix.  This
could even be added later.

Has anyone else on the list attempted anything similar?

David G. Dixon
Professor
Department of Materials Engineering
University of British Columbia
309-6350 Stores Road
Vancouver, B.C.  V6T 1Z4
Canada

Tel 1-604-822-3679
Fax 1-604-822-3619

"PERFECTA FINGAMUS SERVIAT NATURA"

The information in this email and in any attachments is confidential and
intended solely for the attention and use of the named addressee(s).  It
must not be disclosed to any person without the writer's authority.  If you
are not the intended recipient, or a person responsible for delivering it to
the intended recipient, you are not authorized to and must not disclose,
copy, distribute, or retain this message or any part of it.

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Michael Bechard
Sent: Monday, January 05, 2009 9:30 AM
To: Synth DIY
Subject: [sdiy] Matrix patch panels

Hi everybody, I'm trying to put together a semi-modular using a DIY matrix
patch panel, much like the one described here:
http://monopole.ph.qmw.ac.uk/~thomas/synthdiy/patchpanels.htm. There's not a
whole lot of info on the web about doing this, so I figured I'd ping you
guys.

Here's an overview of what I'm planning. My matrix will be a fairly large
(31x28) and combine both audio and control signals, with configurable
switching between unipolar and bipolar attenuation like this:
http://www.cgs.synth.net/modules/cgs33_matrix_mixer_euro.html. However,
instead of using pots for each connection (would be expensive!), I'm using
jacks for switches, much like professor Thomas' design. Each output and each
input will be separately attentuable (pre and post matrix processing) via
knobs setup along each of the matrix's axis. I'm also thinking of using RCA
jacks instead of 2.5mm, since I can get them fairly cheap @ $.25/per at
bulk. The PCB-mounted versions seem to be easiest to use, since the entire
jack housing is metal and forms one or the conductors. I figure I can solder
31 of them directly together to form one row, while using bare copper wire
to connect the other conductors vertically to each other. Here are the RCA
jacks I plan
 to use:
http://mouser.com/Search/ProductDetail.aspx?R=161-0370-Evirtualkey11180000vi
rtualkey161-0370-E. My main concern here is the lack of grounding should I
use these jacks, but I really like the idea of being able to solder an
entire row directly together.

I should also mention I'm a complete newbie when it comes to building synths
(or most any kind of electronics), so please forgive any obvious blunders I
may include in this email and my plans. So far I've only put together a
couple of my modules.

Anyway, I would greatly appreciate any pointers and feedback you guys could
give me on my proposed design. I'm mostly concerned about crosstalk,
grounding, and wire capacitance/inductance at this point. I noticed
professor Thomas used bare copper wire to connect the leads of each jack.
Does anyone know if this works well? How much crosstalk/noise problems
should I expect? Should I plan instead on using grounded jacks, like 2.5mm
stereo? Lastly, do you guys think this design scales well to a matrix the
size of which I am planning?

I'm also wondering about buffering on the inputs and outputs. Since I will
be following Ken Stone's design on the outputs (to get switchable
uni/bipolar attentuation), I know they at least will be buffered. Do you
think I need to buffer the inputs as well, like Ken has designed in the
CGS33? Also, what effect do you guys think the extra current will have on
the signal crosstalk, if any?

Wow, this is a long email, so thanks for reading. I appreciate any and all
input.

Thanks,
Michael Bechard

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