Sorry, I should have mentioned explicitly that I have done the whole dance with resetting tuning tables multiple times and also excluded other sources of variations like the detune/vintage parameter.
In my experience it is fixed to the voice number / card which, at least for me, sticks out like a sore thumb once you noticed the difference for the first time.
If five out of six voices behave identically and one very noticeably different, I highly doubt this is intended in order to make it sound “more vintage”…but more likely either the result of tolerated component variation, or a level of quality control that, at least from my perspective, seems questionable.
I totally agree, if one voice out of six seems wildly different than the others, it tends to point more to a bad voice card IMHO. I will say that for whatever reason, my OB6 seems especially prone to weird behavior involving individual voice variation if I'm not careful about things like MIDI loops (leaving local on, and having track monitor enabled in the DAW for example).
By that I mean I have a number of Sequential synths, and occasionally have these "false positive" conditions where I think the hardware is starting to fail, and yet every time, it turns out to be something about my own configuration that is set wrong. But, this false positive syndrome seems to occur much more often on the OB6 than my other gear.
My relationship with the OB6 has been interesting.. Sometimes in the discovery of false positives, it has felt a little like the type of girlfriend that always manages to make me feel like the bad guy even when my behavior is well within norms by everyone else's standard
. I regard it as sort of an impish little demon of a synth with plenty of "character".... yet because the false positives have always turned out to be my fault and had a clear explanation for why they occurred, it remains a highly regarded piece of gear in my setup.
Oberheim products (at least the ones the OB6 was patterned after) are notorious for misbehavior, no where near as refined as Prophets.
But the symptoms of a bad voice board are what they are on any synth. Do you have a video showing the behavior you could share?