If the popping noise is only on specific voices, then it should be related to
the control voltages that the CPU is writing out for pitch, cutoff, etc.The Z80 writes these over and over, something like 50-100 times each
second or so. If every so often the wrong value was written out, you wouldhear a momentary pop of some kind. Does this only happen when MIDI
data is being received by the CPU? It could be a bug in his code, if so.If he is clocking the CPU faster than the original design, that could causereliability problems, since the circuits were all design with a specific operatingfrequency in mind. Some chips may not propagate the information fast enoughto run at higher clock rates. I am not familiar with the Encore MIDI kit,
so I can't say how it was designed. It could also be an issue with the S&H
analog circuits not working just right at the higher frequency. There may
be a decoder that only affects voices 5-8. Good luck.
From: "richtrix@... [oberheim]" <oberheim@yahoogroups.com>
To: oberheim@yahoogroups.com
Sent: Wednesday, February 25, 2015 1:54 AM
Subject: Re: [oberheim] Finding Clock frequency of my OBXa [1 Attachment]Message
Re: [oberheim] Finding Clock frequency of my OBXa [1 Attachment]
2015-02-25 by Bob Grieb