Wed Jan 12 18:34:26 EST 2011

Prophet 5: A/D and D/A resolution

I found the Prophet 5 service manual[1], as it is a nice example of a
digitally controlled analog instrument.  Made me think: maybe high a/d
resolution isn't so necessary for storing patches: approximate
settings are just fine.  It's when D->A is used for continuous control
that problems arise.

The prophet uses 7 bits for most CVs. and 14 for the frequency CVs to
allow for fine tuning.  Tuning happens in octaves.

The Prophet uses a single 16 DAC for both D/A (synth control) and A/D
(potentiometer readout), combined with CD4051 ($30 Tayda, $50
Futurlec) analog muxes and sample-and-hold circuitry.

[1] http://www.hylander.com/moogschematics.html