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Buchla Matrix Mixer Clone
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Serenadi



Joined: Jul 03, 2007
Posts: 89
Location: Germany

PostPosted: Fri Jan 23, 2009 3:04 am    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
... - this way i would have buffered inputs (no error), a non-inverting matrix mixer and lower part count. with selected resistors it should be suitable for keyboard voltages too (but what different keyboard voltages should one want to mix?).


You're absolutely right.
This way I built my matrix mixer too.

About the keyboard voltages: You may want to mix a single keyboard voltage and an LFO for example into an 1V/Okt input. So it's not a failure to have an accurate 1:1 mixer.
But in this case it won't be bad to look for very low offset OpAmps too (like LT1013).
.
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fonik



Joined: Jun 07, 2006
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PostPosted: Fri Jan 23, 2009 3:09 am    Post subject: Reply with quote  Mark this post and the followings unread

Serenadi wrote:
About the keyboard voltages: You may want to mix a single keyboard voltage and an LFO for example into an 1V/Okt input. So it's not a failure to have an accurate 1:1 mixer.
But in this case it won't be bad to look for very low offset OpAmps too (like LT1013).

thanks for that pointer. i would not have thought of that.

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macumbista



Joined: Sep 12, 2007
Posts: 398
Location: berlin
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PostPosted: Sun Jan 25, 2009 7:04 am    Post subject: Reply with quote  Mark this post and the followings unread

Here's my take on this. I used the CGS 33 Matrix mixer input boards, and for the columns I simply used the schemo from the CGS 04 DC mixer.

Eventually, 8 players will sit around this mixer, each playing a self-made audio circuit (Schmidt-Trigger square wave oscillators with a vactrol FM input), and their signals will be routed to each other according to a projected graphical score.

Some photos and audio from this new mixer follow. Thanks go to Ken Stone/CGS in Australia for providing some of the PCBs used and Katrin Heidorn in Berlin for help with metal fabrication in the case. The case itself is salvaged from my very first synthesizer, an SN76477 pinballgame-based sound generator that I constructed in 2001 when I was supposed to be writing my English thesis. Metal sourced and cut at Modulor.de.

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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My interest in this mixer comes from two areas. One is the ability to create dense interconnected drones, and the other is to be able to cross-modulate tiny, unique sound events. The following track is an example of the latter, and involves 4 oscillators and a digital delay run through the matrix mixer as well as my cheap Behringer desktop console. "Skinned Teeth" is in honor of the mild food poisoning I had at 6am today, and is what my mouth feels like as I write this...


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Last edited by macumbista on Sun Jan 25, 2009 3:57 pm; edited 2 times in total
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vtl5c3



Joined: Sep 08, 2006
Posts: 425
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PostPosted: Sun Jan 25, 2009 11:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Macumbista,

That looks very nice! Those Davies knobs are great for dense panels like that.

Viel Spass mit dem Ding!

Romeo
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funkyfarm



Joined: Jan 21, 2007
Posts: 583
Location: France
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PostPosted: Sun Jan 25, 2009 12:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

macumbista wrote:
each playing a self-made audio circuit (Schmidt-Trigger square wave oscillators with a vactrol FM input)



hmmm !

Was ist das ?


Smile
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macumbista



Joined: Sep 12, 2007
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PostPosted: Sun Jan 25, 2009 3:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

Typical Schmidt trigger oscillator:

http://fluxmonkey.com/electronoize/4093_Oscillator.htm

where the feedback resistor is replaced with a vactrol (DIY = LED + photoresistor shrink-tubed together) + LED driver:

http://www.cgs.synth.net/modules/cgsld.html

My attempt at FM control, with optional gain poti and maybe offset if I want to make it more complicated than it needs to be really. It's for a series of workshops, so it has to be cheap + easy to build. We'll see how it works out! Wink

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funkyfarm



Joined: Jan 21, 2007
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PostPosted: Tue Jan 27, 2009 6:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thank you
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LektroiD



Joined: Aug 23, 2008
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PostPosted: Wed Jan 28, 2009 12:21 am    Post subject: Reply with quote  Mark this post and the followings unread

that would surely cost a fortune in pots?
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neandrewthal



Joined: May 11, 2007
Posts: 672
Location: Canada

PostPosted: Wed Jan 28, 2009 12:40 am    Post subject: Reply with quote  Mark this post and the followings unread

LektroiD wrote:
that would surely cost a fortune in pots?

I Spy G&H pots. IIRC they are something like $.09(yes 9 cents)each in quantities of 1000.

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Luka



Joined: Jun 29, 2007
Posts: 1003
Location: Melb.

PostPosted: Wed Jan 28, 2009 1:22 am    Post subject: Reply with quote  Mark this post and the followings unread

where from?
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macumbista



Joined: Sep 12, 2007
Posts: 398
Location: berlin
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PostPosted: Wed Jan 28, 2009 5:21 am    Post subject: Reply with quote  Mark this post and the followings unread

These pots are some kind of Alpha clone. My problem is that they are very tight. Good for fine tuning, bad for live action freakouts. I looked at the Bournes pots for their fast action, but they do cost a fortune. Can anyone recommend cheaper, but still mechanically robust, pots which can be turned very quickly?

Other folks also recommended bigger knobs, but as you can see there's not a lot of panel space on this mixer! I was also curious about ways of getting these pots looser without destroying them. Deoxit fader lube was suggested on the SDIY list, but maybe that breaks down the contacts over time?

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synthbob



Joined: Nov 12, 2009
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PostPosted: Thu Nov 12, 2009 11:22 am    Post subject: Just the ticket Reply with quote  Mark this post and the followings unread

Hi,

Sorry for joining and then reviving such an old thread but I'm looking to make a (preferably bi-polar) 8 x 8 (or probably 6 x 6 will do me) matrix mixer.

I came across this forum and subject in a google search and must say it looks lovely !

I'm competent at electronincs, but to be honest, mostly wiring, and my days making pcb's from schematics are well behind me and forgotten.

I havn't got the physical ability to make pcb's. And I think I've lost my ability to even breadboard a schematic together, but feel confident with a simple (if big) wiring job.

Are any of the pcb boards available anywhere? So I've just got the housing and wiring left to do?

Sorry if this seems silly for you guys and girls who design circuits in your sleep.

Any help appreciated

Rob
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macumbista



Joined: Sep 12, 2007
Posts: 398
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PostPosted: Thu Nov 12, 2009 12:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ken Stone used to have some matrix mixer PCBs:

http://www.cgs.synth.net/modules/cgs33_matrix_mixer_euro.html

which can be wired for bipolar. You get them the channels multiples of 4. They are listed as out of stock so I'm not sure when or if he'll get more...

Having made an 8x8 matrix, I have to say it's far too many knobs for me to keep track of while I improvise. I made a smaller 4x4 using the CGS33 row input board and several of Ken's DC mixer PCBs:

http://www.cgs.synth.net/modules/cgs04_mix.html

To make a 4x6, for example, it would be easier to do it this way since you have a separate summing mixer for each output column you want to add.

If you don't want to do any boards yourself, I can highly recommend that site for all kinds of nice projects.

Good luck!

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synthbob



Joined: Nov 12, 2009
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PostPosted: Fri Nov 27, 2009 5:04 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks so much for the speedy response, I feel embarrased to have taken so long to reply Smile

Looks like theres no PCB's left, but on closer inspection, hey, its not that bad....breadboard here we come !!!

As side note, you know, I'm thinking I dont need bi-polar, I mean, I want to use this for feeds/returns to a bunch of guitar pedals, audio signals only, and correct me if I'm wrong, and inverted audio signal may cause some minor phasing which could be interesting but not really worth it.

Cheers again!

Rob
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Ruebezahl



Joined: Mar 09, 2014
Posts: 84
Location: Taiwan
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PostPosted: Mon Nov 10, 2014 12:32 am    Post subject: Reply with quote  Mark this post and the followings unread

I am digging out this topic because i am planning on convert my 3x3 passive matrix mixer into an active one. I wanted to build it after the schematics from Ken Stone, already discussed in this thread before: http://www.cgs.synth.net/modules/cgs33_matrix_mixer_euro.html

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.


However i would like to change some thing and need your help:

1. Omitting the second stage of Amplification. I dont really need this bipolar-thing, since i am just mixing Audio-Signals. So first i want to ask if there might be a reason , why its actually still good to have those two stages. and second if i omit one stage, the output will be inverted. I think this shouldnt matter, in Audio-Signals, right? Otherwise, could i work around it, by just make this amp-stage not inverting?

2. Replacing the TL071 with an TL072 They use an TL071 Chip for the buffer, but i dont really see why. It has two extra control-inputs, but they are not used herre anyway. So i want to use TL072 here aswell, saves me ICs. Or would this cause problems?

3. Using a 9V Power Supply I want it to be portable so i dont want to have a +-15V Power Supply and instead power the circuit from a 9V Battery. Shouldn't be a problem i guess, but maybe i have to change some Values of the resistors. Any hints on that?

Thats it, so far. Thank you!

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macumbista



Joined: Sep 12, 2007
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PostPosted: Mon Nov 10, 2014 1:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Ruebezahl wrote:
1. Omitting the second stage of Amplification. I dont really need this bipolar-thing, since i am just mixing Audio-Signals. So first i want to ask if there might be a reason , why its actually still good to have those two stages. and second if i omit one stage, the output will be inverted. I think this shouldnt matter, in Audio-Signals, right? Otherwise, could i work around it, by just make this amp-stage not inverting?


Yes that is correct. Consider however that mixing the inverted signal back with the original signal will cancel it out. Whether or not this happens depends on how you connect everything together.

Ruebezahl wrote:
2. Replacing the TL071 with an TL072 They use an TL071 Chip for the buffer, but i dont really see why. It has two extra control-inputs, but they are not used herre anyway. So i want to use TL072 here aswell, saves me ICs. Or would this cause problems?


Correct. If you don't mind an inverting mixer setup, use a TL071 and mind the pin numbers.

Ruebezahl wrote:
3. Using a 9V Power Supply I want it to be portable so i dont want to have a +-15V Power Supply and instead power the circuit from a 9V Battery. Shouldn't be a problem i guess, but maybe i have to change some Values of the resistors. Any hints on that?


Changing a circuit from dual-supply to single supply means changing the way the op amps are wired. This mainly involves creating a "floating" ground halfway between 0V and 9V, at the non-inverting input in this case. Google "single supply op amp mixer" for some examples. Easiest would would be to use two 9V batteries instead for your dual-supply power source. In my experience, single-supply mixers and much noisier than dual-supply, by the way. It might also be worthwhile to look into op amps specifically designed for single supply like the 741.

Good luck!

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Ruebezahl



Joined: Mar 09, 2014
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PostPosted: Mon Nov 10, 2014 1:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey i slept a night over it and i think i stick to the original schematic and do none of the three aforementioned points Very Happy Considering your points, and me being a beginner, it seems much safer and easier. I will use two 9V-Batteries to have a Dual-Supply. However, I wonder if changing the Voltage to +-9V should i also lower the values of the passive parts like capacitor and resistor?
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macumbista



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PostPosted: Mon Nov 10, 2014 1:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Nah, you're pretty safe with those values. Good luck!
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Ruebezahl



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PostPosted: Tue Dec 09, 2014 9:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

I built the Mixer after the schematics, leaving everything as it is in the schematics. I just used 100k Pots, and a +-9V Power Supply with two Batteries. I skipped the bipolar-option connecting the pin of the pots always to ground.

But it didnt work, how it was intended. There was a Signal going through the mixer, so there was some sound on the outputs, but it was not so loud, even quiter than the output of the synth directly. Also there was a lot of cracking in the background. Also, turning the pots didn't really change the volume.

I then realized that i din't connect the ground of the panel (pots and jacks) to the 0V-Ground of the circuit-board. But after doing so, it was even worse. now there was no sound at all. Even when i checked the sound right at the input-jacks, when there was something plugged in, there was no sound coming through, just crackling. I checked the resistance between the poles of the jack ans just measured 6kiloohm. This is way to less, right? So no wonder there is no sound.

Could it be the pots wired in the wrong way or something? I connected it like here:
Posted Image, might have been reduced in size. Click Image to view fullscreen.

So Input on one side, Output in the middle, Ground on other side.

Or any other ideas what could be wrong?

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macumbista



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PostPosted: Wed Dec 10, 2014 2:31 am    Post subject: Reply with quote  Mark this post and the followings unread

Well, hard to tell without actually seeing it. Check your IC pin numbers, espc if you did any parts substitutions form the original schematic.
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haceka



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PostPosted: Wed Mar 04, 2015 8:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi there,
Thank you VTL5C3 for your post, with your help i realize my version of 205 in 5U

i can explain how i do that if you need !


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