Discussion about the Korg PolySix synthesizer

Hi Malte,

Think we might have a D/A problem here causing instability. Probably why
taking IC6 out of circuit stops the random behaviour. Just looking for
obvious differences between the original board and the clone and one thing
that springs to mind is the D/A buffer op-amp which is used. The spec for
the new board uses a TL072P whereas the original uses a  NJR4560. Seeing as
the rest of the original is covered in generic 4558 and 072 there must have
be a good reason why the designers selected the 4560 in preference. Perhaps
the 072 can¹t switch fast enough of the slew rate is too slow, etc. Time to
get out the datasheets and have careful study I think...

Cheers,
Andy





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