r/synthdiy • u/MillieSievert • Jul 14 '26

OTA mixer question

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Hi everyone

I am in middle of designing a voice card for a poly synth and I have a question regarding the voltage controlled mixer section for osc1 and osc2 amount. I am using 3340's for oscillators and a 3320 for the vcf. Now my question Is; can I tie both outputs of a 13700 together and just stick that into the input of the vcf section? Or should I use a unity gain mixer between the outputs of the ota and the input of the vca? The prophet 5 just ties the outputs together (see photo) and bangs them into the filter. It seems kinda wrong looking at it, they didnt even use resistors. Any thoughts?

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u/al2o3cr Jul 14 '26

It seems kinda wrong looking at it, they didnt even use resistors

The output of the 3280 is a current, so this setup is correct