[sdiy] Fun with the Oberheim M6

[Glen]

At 12:28 PM 8/25/04 , Tim Parkhurst wrote:

>I was running the calibration routines after every chip swap and I did
>notice that the problem was getting slightly better (still noticeable, but
>not as bad). Well, on a lark I decided to run the calibration three or four
>times and THAT CURED THE PROBLEM! John M and I both thought that maybe the
>VCFs were out of 'tune' far enough that they couldn't be brought back by a
>single recalibration, and that the internal processor was able to bring them
>back a little closer each time (each run building on the results of the
>previous).
>
>Has anybody had this sort of thing happen? Perhaps it’s a lesson for all of
>us using micro-driven analog equipment.

I'm not saying your theory is wrong, but I wonder if the unit simply needed
to warm up to full temperature and let its circuitry stabilize? Did you
make sure to let the unit run for an extended period of time before doing
the tuning?

Of course, some of your discrete circuitry might have drifted in value over
the years, and those VCF's might have just barely been within range of the
internal processor's correction capability. Had the discrete parts been
closer to perfect, perhaps the "oughta-tune" button would have worked the
first time?

Anyway, it's good that you finally got it working.


congratulations,
Glen