Your MOTM 300 calibration is off. You should be able to get your MOTM 300s to track
the entire range of at least one of your two controllers. If the controllers are
not consistent with each other, then you need to calibrate one of the controllers.
I found the best way to calibrate '300s was to set up the controller with the MOTM
300s (loaded with other CVs off the controller, just like you plan to use) and
calibrate the 300 using a digital tuner. You should be able to make it linear over
a very wide range.
I don't plan to change any of the resistors in my 300s. Once the 300s are
calibrated, I find that any minor differences between them adds a bit of character
(you get a whole lot of this "character" from Moog oscillators!) and the amount they
are flat is tiny compared to the loading on the controller and other factors.
Eric
P.S. I just had my Moog oscillators calibrated over the weekend. It is not
something I would attempt on my own and you have to compromise on the linearity in
various ranges, but that is part of the sound and character. I tend to think of the
Moog oscillator calibration like piano tuning, you need it done every 6 months or so
and it costs more... So, be thankful that you can calibrate your 300s yourself
fairly easily!
--- thomas white <
djthomaswhite@...> wrote:
> Hey fellas,
>
> I have noticed in my two VCO system that when I use the transpose switch on
> my Roland M-181 keyboard or play higher up in scale thru my Kenton that the
> VCO's do start to sound flat or slightly off key. Especially one compared to
> the other. Could be my calibration (Unique problem to me) It is not a big
> difference, but in a live situation I would have to re-adjust the tuning of
> the 300's on the fly. Not very easy to do in an accurate fashion on stage
> right? Who out there plans to change these resistors and has anybody else
> had similar problems? Thanks loyal friends,
>
> Thomas White
>
> "MOTM 300", Still one thousand miles ahead of the competitors and a million
> miles ahead of the Moog VCO's! Has anybody ever thought about trying to get
> together some beautiful MOTM cheerleaders? JK
>
>
> >From: "Paul Schreiber" <synth1@...>
> >Reply-To: motm@egroups.com
> >To: "MOTM listserv" <motm@egroups.com>
> >Subject: [motm] MOTM-300 resistor change
> >Date: Sun, 13 Aug 2000 21:23:21 -0500
> >
> >∗∗NOTE∗∗
> >
> >This is NOT a required change! Please read the following carefully!
> >
> >∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗∗
> >
> >All new MOTM-300 kits will be shipped with R50 changed from 3M to 2M2 (also
> >called 2.2M).
> >
> >Assembled MOTM-300s will have a 2M2 or a 1M8 depending on the particular
> >performance
> >of that circuit.
> >
> >This resistor adjusts the "High Frequency Track" of the VCO. Specifically,
> >the tracking accuracy from 500Hz
> >and up. No, I can't make it a pot because that causes more problems than it
> >fixes.
> >
> >Newer batches of the MAT02EH NPN transistor used in the exponential
> >converter show ∗improved∗ HFT
> >when R50 is lowered.
> >
> >Now, should you immediated tear apart your MOTM-300 to replace this?
> >NONONONONONONO!
> >
> >∗ONLY IF∗ you think that in tracking multiple VCOs ABOVE 500Hz you have an
> >issue, then you
> >can change this resistor. You WILL HAVE TO RECALIBRATE THE VCO IF YOU DO
> >THIS!!
> >
> >The following is the tracking of 1 VCO with R50 changed. Voltage source is
> >Pro-2000. Errors in the Pro-2200
> >are included in this (about 700uV over the range).
> >
> >Desired Actual With R50 = 3M
> >25 24.97 24.91
> >50 49.98 49.92
> >100 100.01 100.2
> >200 200.07 200.18
> >400 400.06 399.97
> >800 799.97 796.1
> >1600 1599.5 1587.2
> >3200 3197 3180
> >6400 6386 6369
> >
> >This is an improved ∗average∗ error over 8 octaves of 0.065% Let's see
> >anybody else top this!! :)
> >
> >You can see how the VCO "runs flat" in the upper octaves. Now, can you
> >∗hear∗ this? Probably NOT!
> >But, if you are 'zero beating' VCOs without sync in lower octaves and want
> >to maintain that in the upper
> >ones, the lower value resistor will help.
> >
> >If you want a freebie 2M2 resistor(s), send me email.
> >
> >Paul S.
> >
> >
> >
> >
> >
> >
> >
>
> ________________________________________________________________________
> Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
>
>
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