Archive of the former Yahoo!Groups mailing list: MOTM

Happy New Year All!

As promised, here are my observations/comparisons of the MOTM 300 VCOs and
MOTM 420 VCF vs. some Moog modular stuff. This is all very subjective and
it is certain that YMMV!

The setup:
- Encore Expressionist MIDI/CV Converter -> Moog Modular CV/Trigger inputs
- CV -> Moog 901A Oscillator Controller controlling a few 901B Oscillators
- CV -> Moog 904A Low Pass Filter
- Same CV mult'd -> two MOTM 300 1V/Oct inputs and MOTM 420 1V/Oct input
- MOTM 300 outputs and Moog 901B outputs -> Moog mixer panel
- One mixer output -> MOTM 420 input and the other output -> Moog 904A
filter input
- Both filters input -> the same Moog 901 VCA
- One Moog 911 EG -> the VC inputs of both filters
- One Moog 911 EG -> the VC input of the Moog 901 VCA
- Output of the VCA -> trunk lines -> mixer/power amp
For the waveform tests, I ran the output of the Moog mixer panel directly
to the VCA. The Moog modules are all R.A. Moog modules from around 1969.

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. 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. The
901B has no PWM, no Sync, and no linear FM. The output of the MOTM 300 is
very hot, about twice the level of the 901B. I'd love to do these same
tests with some Moog 921 oscillators if I could find some!

- Sawtooth Waves: No major difference. The MOTM might be a tad
brighter/buzzier but it was really hard to judge. The mid harmonics might
be coming out more. 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 is
something really wild happening when combining these different oscillators
running off different power supplies.

- Sine Waves: Very small difference. The 901B sine had a few more
harmonics in it making it sound slightly more nasal than the MOTM. Both
seemed to have a few extra harmonics so I might be picking up a tad bit of
distortion elsewhere in the signal path (VCAs, mixer panels, etc.) but it
was quite musical.

- Triangle Waves: There was pronounced difference between these waveforms.
The MOTM had a more "hollow" sound while the Moog seemed to have a
"rounder" sound. They are both recognizable as triangle when compared with
Saw and Pulse but there is a difference. I dare say that I think I prefer
the Moog triangle wave in this case because it sounds a bit "fatter" than
the MOTM.

- Pulse Waves: These are certainly different. The Moog Pulse Width
control needs to be set fully to the right to get close to a square wave.
Even at that it doesn't sound as fully "square" as the MOTM VCO in the
center of the dial. There is a tad bit more buzz in the Moog VCO, leading
me to believe it isn't quite square. At the narrowest setting (fully left
on the Moog and fully right on the MOTM), the sounds were very close but
the Moog had just a bit more nasal quality to it. The MOTM PW that is
fully to the left is quite different from any of the Moog PW settings.
Sweeping the PW on both sounds quite good although the Moog PW is
equivalent to only the right half of the MOTM PW. Both are quite good
sounding!

That's enough for now. I'll write up some more notes on the filter tests
soon. The filters are ∗very∗ different beasts! I hope this is at least
interesting. I found it quite educational. If I had a better
oscilliscope, I'd be interested in seeing some of the waveforms but all I
have is an ancient Heathkit that is wonderful for the price I paid for it
(nothing) but can only tell you that what you are seeing is a sawtooth wave
vs. a triangle wave....

Eric