yeah, that TMUX chip looks really good (a little costly though). looking forward to seeing the oscillator when its ready. as for the 4013, youd probably want a buffer of some sort before the output for protection anyways, so level shifting wouldnt be too much added on to that.

also, i just noticed the "new" LM393B variant. it looks like an all around improvement. its faster, cheaper, lower offset voltage and lower bias current. also, whats the difference between the 2903, 293, and 393? i never could discern that from datasheet.

you mean its not oscillating anymore? or that the output has increased in amplitude to go to the rails?

yeah, the lm393 is slightly slower than the 311, but not by too much. you could put some clamps and limiting resistors on the 319, but at that point its more parts than just an extra transistor on the 393, and the cost is more. if you want to share the surrounding circuitry, i might be able to find ...

looks good. you want a signal to go +/-100mV at pin4 of the LM13700. maybe the best way to do this, is to put a 100k pot between +/-12V, so the wiper can go between the extremes of voltage. and then use a 100k and 1k to make a voltage divider connected to pin4, to know the +/-12V down to +/-120mV. t...

theres also the LM161/361 but they have high input bias current (but are ridiculously fast). although not quite dual, just dual output.

i think the LM319 is it, although it has a different input stage that cant handle more than +/-5V differential input voltage. one trick for the LM393 is to just shift all of your input signals up to 0-12V range, and run it single sided. [EDIT] but, an advantage to the LM319 is that its significantly...

take a look at the alps slide pot datasheet, as they look similar. you can take measurement and match the dimensions in the datasheet to see if they make a good fit.

try replacing the 12k at pin5 of the 072 with 1k instead. then its a matter of restricting the range of your trimmer at pin4 of the 13700 to +/-100mV. there are a few other ways to do it, but if that works for you, it would be the easiest. [EDIT] i just realized that will reduce the amplitude. disco...

connect everything up for testing and apply 2V or more of CV. if you dont get something out of the VCA, check the VCF out. if still nothing, apply an external signal to the VCF in and listen at VCF out and VCA out. if those work then its an issuse with the VCO.

yeah, sounds like the chip is no good.

what are the voltages on all pins of the opamp? and what are the voltages on the 100k resistors inputs (points marked -5V and CV on your schematic)? its important to measure right on the parts, as maybe there is breadboard issue. its possible the opamp is fried, but i wouldnt waste the INA on this a...

also, with your expo CV on the VCA, you can apply that straight to Q19 (or Q25) base, which will be fewer components and less parts.

thats correct, it should go to 5V. try disconnecting the line to the arduino and measure at the opamp output. if your arduino is running at 3.3V, then it will clamp the output at 3.7V or so.

looking good! the diodes will effect the pitch a bit. as they change temperature, they will leak current a bit more or less, so it all depends upon how much of a change this is. if its on the pA level, then it wont really matter. you can give it a try and see. i find that the glass bead diodes leak ...

if you something on your computer that can do FFT (audacity, etc) that might be the best resolution for this.

glad that worked out. im a little curious as well as to how this design ended up lasting this long.

measure that right at the output of the buffer amp.

you can just probe at the output. if you insert a stereo signal you can check the crosstalk and distortion of the bypass circuit. then you can swap out those opamps, etc and see if that changes at all.

well, if your getting exact 1.000V steps on the octave switch, and the HF doesnt bring it into tune, then the issue is the finite reset time on the integration capacitor. the HF tracking deals with the exponential converter error, but the finite reset time creates another error. the circuit would ha...

the LV and HC etc series of 4053 can only handle 10V, and the midiverb is setup for 17V. i was curious if you measured the distortion and crosstalk just to see how it compares to the theoretical limit of the DAC, etc. it might be a good way to see how much difference each modification makes. so you ...

that seems like a decent switch, i wonder if any of the DG series would work for you. is this for the midiverb? have you measured the current performanc doing a clean pass-through (if possible).

you can replace them with individual switches to reduce crosstalk, although im not certain that the distortion would change much. there are switches with lower charge injection, which might help, but that S/H cap is pretty big, so the typical pC of injection might not be the issue. is the switch the...

is this while doing the HF tracking adjust?

sounds awesome! also like the mashup of halloween and valentines day.