Posted: Thu Jun 26, 2008 6:31 pm Post subject:
Buchla Matrix Mixer Clone
In preparation for an upcoming surround sound gig, I built an 8x8 matrix mixer, using the Buchla 205 schematic as my guide. It was a fairly easy build - most of the wiring I did directly on the pots, creating a column style buss with them. That's really all a matrix mixer is - rows & columns, like an excel spreadsheet or an HTML table. You have your 8 inputs, that you can bring up at different volumes on each of the 8 outputs. In my first audio test, I simply connected 8 oscillators, using different waveforms and each running at a different frequency. Fading the inputs in and out on one of the output columns reminded me of wavetable synthesis, but very manual. I think you can do some incredible sound collage with a tool like this.
I'll try to record a few samples later on. I'll post the press & peel pcb layout, once I make some corrections.
Cheers all,
Romeo Last edited by vtl5c3 on Tue Nov 11, 2008 8:22 am; edited 1 time in total
No, I used sockets thinking I'd start with LF353s and if they didn't sound good, I'd try OP275s. So far the 353s are doing a great job, so I doubt I'll bother trying anything else for now.
Eric, I will post some photos over the weekend.
Mr. Clack, Very true about the CGS matrix mixer. I have one of those too, but I'm dedicating it for CV mixing. Keeping it close to my sequencers. The plan is to use it to create sequence variations, transpositions, etc... for polyphonic playing.
The reason I built the 205 is that I already had two assembled DIY boards. It's really a simple circuit, basically 6 dual opamps, a few caps and resistors, the rest is done with a buttload of panel wiring.
I'll get the PCB layout, some photos and samples uploaded in the next few days. Got to recover from the work week a bit first.
Joined: Jun 29, 2007 Posts: 1113 Location: Loss Angeles
Audio files: 3
Posted: Fri Jun 27, 2008 5:44 pm Post subject:
The original uses single opamps. Were the crosstalk/isolation specs that much worse back then? OP275s will likely sound a bit different than Buchla's original design
This sounds like a fun module to build. (except for the wiring! )
What value are the pots? I've got heap of pots building up from stripped mixers etc. and want to find a use for them. _________________ What makes a space ours, is what we put there, and what we do there.
Yes, but, that then ties you down to a specific size and type of pot and socket. Which probably means going out and buying them. _________________ What makes a space ours, is what we put there, and what we do there.
As promised, here's some audio. The first track is 8 static vcos crossfaded into one output channel. Not too exciting, but gives you the general idea. The second track is 8 vcos, this time sequenced with superseque and milton, crossfaded into 8 outputs.
8x8_mix_test1.mp3
Description:
8 vcos, static pitch, crossfading between to change tonal palette.
Filesize:
1.84 MB
Duration:
2:01
Viewed:
3003 Time(s)
8x8_stereo_out_sequenceMix.mp3
Description:
8 vcos sequenced with superseque and milton. Crossfading between 8 inputs and 2 outputs
Joined: Feb 28, 2008 Posts: 161 Location: chicago
Audio files: 9
Posted: Sat Jun 28, 2008 4:54 pm Post subject:
feedback is where matrix mixers really get exciting
with a 3x3 mixer you could have two of the outputs go to filters/effects and back into two inputs and then throw a sound into the leftover input and listen to it from the leftover output...
now you can adjust the signal flow to have the effects go from series to parallel, with or without self-oscillate etc
now most of you know that.... but rerouting signals and crosspatching via knobs can get me worked up you know
I must have one of these! Imagine how amazing it would be in conjunction with the CGS sequential switch. The thought of sequencing through 8 different mixes of control or audio signals vith varying degrees of feedback blows my mind _________________ " I went through quite a few trannies til I found one I liked" - Wild Zebra
very cool. gotta say i'm having a hard time imagining needing 8x8 (thinking "that's more than $50 just for the knobs")... i have one of ken's 5x5s, and i don't think i've ever maxed it out... anyway, thanks for sharing, and the schemo!
I'd like to build one of these. I'm not sure if I'd build all 8 channels, but I would definitely use the PCB layout if it gets posted. Thanks for putting this stuff up.
OK, and here's the PCB layout. As you can see it's nothing fancy, just 6 dual opamps configured as summing opamps. The Buchla 205 had 4 opamps for one side (left), 4 for the other (right), and another 4 for both channels (L&R). There was also an opamp for the monitor outputs, but I left that off.
The Buchla 205 has two sections that are both 5 input mixers where any of the 5 inputs can be sent to any of 4 outputs. In addition to the 4 outputs, there's an extra 4 outputs that are mixes of both sections.
For the live gig, I will be feeding 8 vcas into each of the matrix inputs and directing them to 6 monitors in the performance space. I will use the 2 additional outputs as effect sends. That's where I'll probably get some wacky feedback going!
Uncle Krunkus wrote:
I'm still trying to work out what it does and how it does it!
Concerning the Matrix Mixer schematic on Doepfer's site:
"For each of the outputs the two OpAmp circuit with the corresponding output socket is required."
Could anyone explain to me why they have two opamps buffering each output? Why couldn't they have had just one opamp per output and doubled the feedback resistor value?
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Buchla Matrix Mixer Clone
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