[sdiy] Prophet 600 tuning question

Tom Wiltshire tom at electricdruid.net
Sun Feb 26 14:32:22 CET 2012

From looking at the schematics, I'd say there's no simple adjustment for it. Doug's right - moving the knob is probably easiest.

The Master Tune knob seems to be just a control read by the ADC and then used by the uP to adjust the CVs sent to the voices. There's no adjustments for all the voice CVs - the CV comes from the DAC to an S/H cell and then directly to the voice. No summer or anything in between.

Given that the uP is using its own clock frequency as the basic time reference, presumably you could retune the whole instrument a little by tweaking the 8MHz master uP clock. It's possible that this has drifted a bit over the years. Aside from that, I can't really see a way to do it.


On 26 Feb 2012, at 02:18, luther rochester wrote:

> When my 600 tunes up, all 6 voices are in tune with each other and scaled fine over octaves. But all notes on the synth are a bit flat. I have to keep the Master Tune knob at about +3 in order for it in tune to properly to other instruments.
> I've read the scaling procedure and it seems relatively painless, but it also doesn't seem like it would address this problem. Is there some other kind of offset adjustment I can make so keeping the Master Tune at 0 will mean the synth will be in tune?
> Thanks
> -- 
> ./luther
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