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by guest
Sat Jan 16, 2021 10:24 pm
Forum: Music Tech DIY
Topic: Polyphonic MIDI to CV Conversion
Replies: 1
Views: 63

Re: Polyphonic MIDI to CV Conversion

i might be able to help. are you looking for more info on the inidividual tasks the code does to achieve the overall goal, or more low level details on how to actually code up those tasks?
by guest
Sat Jan 16, 2021 10:21 pm
Forum: Music Tech DIY
Topic: fsr circuit design feedback
Replies: 47
Views: 456

Re: fsr circuit design feedback

what was the failure mode? did you use switches as you have drawn, or were those replaced with the comparators?
by guest
Sat Jan 16, 2021 9:45 am
Forum: Music Tech DIY
Topic: fsr circuit design feedback
Replies: 47
Views: 456

Re: fsr circuit design feedback

excellent!
by guest
Sat Jan 16, 2021 8:35 am
Forum: Music Tech DIY
Topic: fsr circuit design feedback
Replies: 47
Views: 456

Re: fsr circuit design feedback

you need a seperate diode from each output to the reset point.
by guest
Sat Jan 16, 2021 7:23 am
Forum: Music Tech DIY
Topic: fsr circuit design feedback
Replies: 47
Views: 456

Re: fsr circuit design feedback

also, reset should come from the output of the 40106 not the opamp.
by guest
Sat Jan 16, 2021 7:22 am
Forum: Music Tech DIY
Topic: fsr circuit design feedback
Replies: 47
Views: 456

Re: fsr circuit design feedback

what happens if you just put the pots on the 40106 outputs and dont use the 4066?
by guest
Sat Jan 16, 2021 7:16 am
Forum: Music Tech DIY
Topic: fsr circuit design feedback
Replies: 47
Views: 456

Re: fsr circuit design feedback

yes, if you want to flip the polarity, then an attenvuerter will work well, or a switch.

they should all be mixed into an inverting opamp.
by guest
Sat Jan 16, 2021 1:42 am
Forum: Music Tech DIY
Topic: Learning to debug Frequency Central XVCO2 build
Replies: 28
Views: 191

Re: Learning to debug Frequency Central XVCO2 build

so, if you plug in the module and apply an external CV (or turn the tune knob) you should see pin2 go up and down by 18mV per octave.
by guest
Sat Jan 16, 2021 1:02 am
Forum: Music Tech DIY
Topic: Learning to debug Frequency Central XVCO2 build
Replies: 28
Views: 191

Re: Learning to debug Frequency Central XVCO2 build

ok, that actually doesnt seem too bad. did you try an extrnal CV? it looks like its beeing driven really hard into the subaudio range. pin2 should go +/-100mV.

the difference between the base and emitter voltages is about 0.6-0.9 on most of them.
by guest
Fri Jan 15, 2021 9:05 pm
Forum: Music Tech DIY
Topic: Learning to debug Frequency Central XVCO2 build
Replies: 28
Views: 191

Re: Learning to debug Frequency Central XVCO2 build

you can also apply an external CV to see if you can get the oscillator to go to higher frequencies.
by guest
Fri Jan 15, 2021 9:00 pm
Forum: Music Tech DIY
Topic: Learning to debug Frequency Central XVCO2 build
Replies: 28
Views: 191

Re: Learning to debug Frequency Central XVCO2 build

one quick thing to check, is measuring the voltages on the 3406. all of the Vbe drops should be 0.6V.
by guest
Fri Jan 15, 2021 8:54 pm
Forum: Music Tech DIY
Topic: LM339 Pullup resistor value
Replies: 15
Views: 147

Re: LM339 Pullup resistor value

in case it wasnt clear above, if your 4017 is running of 12V, your LM339 needs to go to 12V. if the 4017 is at 5V, then the LM339 should be at 5V. mixing the levels up can cause higher than normal current draw. the resistor only controls the rise time, the fall time will still be very fast. with a 1...
by guest
Fri Jan 15, 2021 8:48 pm
Forum: Music Tech DIY
Topic: Potientometer Replacement for MFB Microzweg
Replies: 12
Views: 183

Re: Potientometer Replacement for MFB Microzweg

awesome, glad its back to making music. and thanks for posting back, hopefully someone in the future benefits from that.
by guest
Fri Jan 15, 2021 8:33 pm
Forum: Music Tech DIY
Topic: Adding sync to OTA VCO?
Replies: 10
Views: 887

Re: Adding sync to OTA VCO?

looking at it again, i think it would be best to run a 10k resistor from the juncture that goes to the first OTA up to the +input. this will help decouple the two OTAs so the sync signal doesnt effect the frequency when it doesnt cross the threshold. then put your 1nF cap to the +input. and you will...
by guest
Fri Jan 15, 2021 7:14 am
Forum: Music Tech DIY
Topic: fsr circuit design feedback
Replies: 47
Views: 456

Re: fsr circuit design feedback

left hand is output of the opamp (before your diode, etc), and the right hand is the output of the other 2 schmitt trigger ciruits (each with their own diode).
by guest
Fri Jan 15, 2021 7:13 am
Forum: Music Tech DIY
Topic: LM339 Pullup resistor value
Replies: 15
Views: 147

Re: LM339 Pullup resistor value

yes, thats correct. putting capacitors across the power rails can help some, but only for short durations of extra power draw.
by guest
Fri Jan 15, 2021 5:52 am
Forum: Music Tech DIY
Topic: LM339 Pullup resistor value
Replies: 15
Views: 147

Re: LM339 Pullup resistor value

when the LM339 output goes low, the 3.3k is connected between +V and ground, so if thats a 12V rail, thats 3.6mA being drawn. if you added another 3.3k for each channle, then thats 14.4mA for four channels. if theres a bit of resistance in your powerupply line, that extra current can cause a voltage...
by guest
Fri Jan 15, 2021 5:23 am
Forum: Music Tech DIY
Topic: fsr circuit design feedback
Replies: 47
Views: 456

Re: fsr circuit design feedback

starting with that is fine. all those diodes and transistors will cause offset issues, but will be a great starting point.
by guest
Fri Jan 15, 2021 4:22 am
Forum: Music Tech DIY
Topic: Learning to debug Frequency Central XVCO2 build
Replies: 28
Views: 191

Re: Learning to debug Frequency Central XVCO2 build

ok, there is something wonky besides for the trimpot issue, as that shouldnt effect it making sound at all. did you test it after soldering that resistor down where it should go?
by guest
Fri Jan 15, 2021 4:14 am
Forum: Music Tech DIY
Topic: fsr circuit design feedback
Replies: 47
Views: 456

Re: fsr circuit design feedback

how about something like this: http://falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWcMBMcUHYMGZIA4UA2ATmIxAUgosgCgw9sQUUAWZ-ZjFDvKKaEjDRChENmjYmSOgya52aPtgQ8l-GEJFiJU6nQBOXNZwW9+YeIeZtzYDGPVVL8WgHdwDu17ZU6H+0dWKhU1YKh3cVVmcNDzOgBjcUhFUxTwVnZnAFMAWmIBSHswVlC8MGIUPHwMVjEYODBaJJZ2ErbCZ0yLPIKEWGL...
by guest
Thu Jan 14, 2021 9:44 pm
Forum: Music Tech DIY
Topic: Learning to debug Frequency Central XVCO2 build
Replies: 28
Views: 191

Re: Learning to debug Frequency Central XVCO2 build

and if you want to post pictures of the boards, we might be able to spot something. also, what are you using for your 3046?
by guest
Thu Jan 14, 2021 9:20 pm
Forum: Music Tech DIY
Topic: Learning to debug Frequency Central XVCO2 build
Replies: 28
Views: 191

Re: Learning to debug Frequency Central XVCO2 build

yes, that is all correct.
by guest
Thu Jan 14, 2021 9:01 pm
Forum: Music Tech DIY
Topic: Learning to debug Frequency Central XVCO2 build
Replies: 28
Views: 191

Re: Learning to debug Frequency Central XVCO2 build

measure on the trimmer directly - does the middle wiper pin change voltage as you turn it?

give the module a listen - does it make the right sounds, does it generally track 1V/oct?
by guest
Thu Jan 14, 2021 8:44 pm
Forum: Music Tech DIY
Topic: Learning to debug Frequency Central XVCO2 build
Replies: 28
Views: 191

Re: Learning to debug Frequency Central XVCO2 build

also, which trimmer is it? what does it control/whats its label? im guessing this is the temp setting for the heater core.
by guest
Thu Jan 14, 2021 8:40 pm
Forum: Music Tech DIY
Topic: Learning to debug Frequency Central XVCO2 build
Replies: 28
Views: 191

Re: Learning to debug Frequency Central XVCO2 build

is everything else working like it should?

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