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Prophet 6 Osc Temperature Tuning, Calibration, LP Filter

Prophet 6 Osc Temperature Tuning, Calibration, LP Filter
« on: March 06, 2021, 12:33:46 PM »
After getting P6, I documented some findings and thoughts in regards to the behavior of the tuning and calibration of my unit.

Much of this info has been discussed in fragments over the years on this forum or elsewhere, but I did a good amount of additional testing, as I wanted to really understand how it works, and when I should re-run a new tuning calibration.

So, yeah, here's everything you might have ever wondered about temperature tuning and calibration (and then some ;)

https://www.presetpatch.com/articles/Prophet-6-and-OB-6-Tuning-Calibration


I wonder, has anyone else checked the tuning of Low Pass Filter / Self Oscillating Filter Tuning?  The Oscillator Tuning is spot on after calibrating (excellent!), but my unit is consistently about 25-30 cents flat on tuning of self oscillating filter -- over multiple octaves in center of keybed... (based on cutoff knob being quantized to semitones) 

Is this just my unit, or do others get this as well?   If it's others as well, I wonder if the filter tuning could be slightly adjusted / offset?  Or add another global setting like "Master Tune", but just targeting LP Filter offset?  (feature request)

Osc Levels: All Off
Res: 95-100%
Cutoff: 72
F.Env: 0
Key Track: Full (or off)
Slop/Vintage:  0

Sequential Pro 3 and Rev 2 - Sound Sets, Patch Banks - Available on Sellfy: https://sellfy.com/sounddesign/

MPM

Re: Prophet 6 Osc Temperature Tuning, Calibration, LP Filter
« Reply #1 on: April 07, 2021, 04:36:10 PM »
I wonder, has anyone else checked the tuning of Low Pass Filter / Self Oscillating Filter Tuning?  The Oscillator Tuning is spot on after calibrating (excellent!), but my unit is consistently about 25-30 cents flat on tuning of self oscillating filter -- over multiple octaves in center of keybed... (based on cutoff knob being quantized to semitones) 

Key Track: Full (or off)

I don't have a CRO, or anything similar to test this, but gave it a shot with my ears that by now probably can't discern anything above 12kHz. Okay, 11kHz :-\
I couldn't perceive anything really, but it got me thinking about "stretch tuning" in pianos, and if the Prophet~6 is a bit flat at the bottom end and normal at the top end, it's probably not so bad really. And playing a C2 plus C4 or C5 sounded just fine, to me.
OB-6  Prophet-6  Prophet.Rev2/16  no kids