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Another Mod Your CL: Tetrax
MUFF WIGGLER Forum Index -> Ciat-Lonbarde  
Author Another Mod Your CL: Tetrax
thresholdpeople
Hi all,

I've been day dreaming about how awesome it would be to have control over the VCAs on the Tetrax, like how Meng Qi has done for the Sidrassi on his Squishable.

The barres control the opening and closing of the two VCAs - I assume it would be a relative simple banana jack somewhere in the circuit post barres.. Has anyone done it? Is the release VCA based on the closing of the press VCA, or does it actually follow the voltage drop of the piezo? Would it need some sort of mixer to account for still using the barres?

There isn't any space on top of the Tet to stick the jacks, unless using some standoffs to account for the PCB and putting them above the knob CV inputs. Otherwise they can go below the pcb inline with the barres, either in front or in back of the instrument.

Thanks!
Boris
Repeater
I talked with Peter about this once. He said it's as simple as replacing the piezos with banana jacks. If you want both barre pressure CVs and an AM CV input, you'll need to add a mixer.
thresholdpeople
Thanks Repeater!

Do you know how the release gesture works? Would that be on a separate banana jack, or does that voltage go high when the press gesture goes low?
Repeater
thresholdpeople wrote:
Thanks Repeater!

Do you know how the release gesture works? Would that be on a separate banana jack, or does that voltage go high when the press gesture goes low?


From the Tetrazzi assembly manual:

"connect to the signal pin of PIZ to modulate amplitude with an external LFO. this is cool because of the stereo response. connect a capacitor in beseries [in between in series] of the signal .1 microfarad or greater, to have the signal normalized to silence, peaking left and right with upwards and downwards gestures respectfully."

There's some more info and generalized schematics in the manual:
https://docs.google.com/document/d/15YufBEtuCzgu2H8mu9EkYxsxM2j4sXejsp T7Kb8MfSs/preview#
windspirit
Im modding a sid right now and peter told me that you can just hook up a signal without any caps. Piezos make very high voltages for a tiny moment and they are bipolar so those inputs should be able to handle whatever you throw at them. That being said I am not to blame if you set your sidrassi on fire somehow Dead Banana
thresholdpeople
Meng Qi's AM mod on the Squishable has no sound at 4.5v, channel one between >4.5-9v, and channel two between <4.5-0v.

Is it the same with your Sid, Windspirit?

Is the piezo ground wire just that? Will you be ignoring it for your AM inputs? Are you going to make a mixer to use both the barres and voltage? Finding the space to mount all this in is going to be tricky! The banana jacks are doable, extra circuitry makes it much more complicated though.
thresholdpeople
Windspirit where are you putting the jacks on the Sid?
windspirit
Ah sorry, I just have a bare board so I haven't wired it up yet. Are you sending in a DC or AC signal to the squishable? Have you tried contacting Meng Qi directly?
thresholdpeople
It isn't for the Squishable. I want to be able to have AM control over my Tetrax.

I'm thinking a normalizing switch and a jack, probably in front of each barre in the bottom base.
thresholdpeople
Ahh.. well, this morning I learned that the red outputs on the Tetrax are the oscillator outputs, not the individual 'channel' outputs, when I ran it into my Coco.

Great! I don't think this mod is necessary any more.

The Tetrax makes a great little partner to the Cocoquantus!
wednesdayayay
When I get some free time I'm really wanting to compile all the forum knowledge here into a nice stick thread per instrument as it seems like there is often much confusion

I'm glad this will work for you the coco is inspiring
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