Fragmare Posted March 8, 2021 Share Posted March 8, 2021 Hey guys, I'm not a programmer, but do a lot of work with Atari chiptune & sound design, and I had a question or two about the difference in pulse frequencies between the original Activision DPC chip from Pitfall II and the newer DPC+ chip in the Harmony cartridge... I've done some tests with sound output from dpctuner.bin, and as we all know, the original DPC has 256 frequencies (really only 224, as 224-255 seem to all be exactly the same)... however, I've noticed only a select few of those frequencies are "pure". The rest seem to be interpolated, microtonal approximations of other "in-between" frequencies. Of which, about ~50 or so line up fairly well with actual note frequencies, when making a note table. My questions are... Does the DPC+ offer better tuning and more pure frequencies than the regular DPC? If so, is there a ROM file out there that showcases all the frequencies of the DPC+, like dpctuner.bin does for the normal DPC? Also, how do either of these chips handle volume when downmixing their 3 channels into a single TIA channel? Do they have their 3 channels pre-set to a volume level that will never exceed the TIA's 4-bit volume register, even when all 3 are combined? Or do they simply mix all 3 channels, and let the TIA's 4-bit volume register clip off any excess that might exceed max volume? Any insight or advice would be appreciated Quote Link to comment Share on other sites More sharing options...
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