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Subject: Re: MOTM Comparisons/Observations

From: "Eric S. Crawley" <esc@...
Date: 2000-01-02

At 11:28 PM 1/1/00 -0600, Paul Schreiber wrote:
>From: "Paul Schreiber" <synth1@...>
>> MOTM 300 VCO vs. Moog 901B VCO:
>> Note: There is a big difference in functionality between these two! The
>> Moog 901B has a wide range but isn't terribly linear.
>The RA Moog tracking is 10 times ∗worse∗ than a '300.
Yes, I forgot to mention that during the testing, I had to tweak the Moog
oscillators a few times to get them back in pitch. I only had to do this
once for the MOTM oscillators and that's because I turned the wrong knob!
I have a digital tuner that I plug into the sine wave output of the
oscillators to keep an eye on the oscillator tuning at any time.

> >Mine have recently
>> been calibrated and do well over 5 octaves with the 8' octave range
>> setting. This doesn't hold true for the other octave range settings.
>That's be cause he had truble finding good capacitors.
Hmm, does that mean if I found some good capacitors, I would be able to
improve the tracking over octave switches?

>> When mixed together, the beating between these two
>> oscillators is ∗really∗ intense. I had them beating about once every 10
>> seconds but the sweep caused by the phase interaction was like a very wild
>> PWM with a pronounced almost sawtooth modulation. I could not get this
>> kind of beating between like oscillators on the Moog or the MOTM. There
>> something really wild happening when combining these different oscillators
>> running off different power supplies.
>What you are hearing is the Moog not tracking with the '300. It's not the
>power supplies.
>This is just the difference in ∗relative∗ tracking with the Encore as the
So this is just a minor difference between the tracking? The funny thing
was that I couldn't detune either the MOTM or the Moog oscillators to get
the kind of phase cancellation that I got with the MOTM and the Moog. Yes,
it changed slightly as I went up and down the keyboard but it was very
pronounced in that the oscillators almost cancelled each other out.
Perhaps this has something to do with direction of the saw waves? I'll
check this out. Perhaps one is saw up while the other is saw down?