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TWO59 VCO module (Building Thread) by FEEDBACK
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page Previous  1, 2, 3, 4, 5, 6 [all]
Author TWO59 VCO module (Building Thread) by FEEDBACK
Scratch that, I put a J201 in the footprint and first one gave me a pretty decent sine wave. You have to redo the transistors legs the same way as the other FET but it seems to work well.

I just put another 68k in parallel with R2 on the front board, hopefully I can get some 1v/o tracking for now until I can hunt down the other problem.
Ok so this oscillator has been working well for me so far BUT the output levels are so much lower than the rest of my oscillator modules, especially the analog ones which are usually 20V peak to peak. All of the outputs on this module are about 2 - 3V peak to peak. I couldn't help but notice the rather unusual output buffer circuitry, mostly the fact that there is no input resistor for the op amps which are set up somewhere between a voltage folllower and an inverting op amp. I managed to increase the amplitude of the sine wave by increasing R17 (I got about 10V p2p with a 68K resistor, Ill probably double the value for 10V p2p) but increasing the feedback resistors of the other buffers resulted in a wave that is a higher amplitude but clamped at the top around 1V. I tried increasing R47 just to see if this would work instead with the unaltered buffer circuit but output is still clamped.

Before I rip out more resistors and solder them back in any suggestions on what parts to tackle to improve this behavior? I don't want to break a trace by repetitive soldering / desoldering.
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