Old Crowe Yamaha CS80 VCO153

via the SDIY list:
"Hey folks, its been a while, but I have this thing in testing right now. This is an equivalent circuit to the IG00153. This differs from my MOTM-style modular 153 oscillator in that it is strictly the VCO IC with a ramp output, linear CV input, current bias input (FT) for octave select and exponential modulation (vibrato) input. It can use the original M-board FET and charge pump capacitor, or those can be
removed and local ones installed. I madethis mainly to see about replacing things at the chip level, but not relying on custom devices. It is 98% SMT parts, with only 3 parts left through-hole for the moment (mainly to swap things and see how the specs change). It no longer needs an input offset trimmer, or external frequency compensation of the input summing amp. The DIL-16 footprint in the middle of the board is used to install it into an actual IG00153 socket. Generally it is low-profile enough to fit between M boards (it does in my CS-50). It has internal temperature compensation of the charge switch and comparator, making it much more stable than the original device. The charge pump core circuit runs on its own internal 10V reference supply.

Eventually I want to craft the entire M-board from standard circuits. The waveshaper is done (it is the one I made for the 153 module). The EGs are done. The filters are done. I know how to buildthe VCA, thats next. In any case here is an image of the board, a bit larger than actual size. More later...

http://www.cs80.com/VCO153_pic.gif

Crow [http://www.cs80.com]
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