Slim Phatty CV mod 1 volt /octave

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Colonel Monk
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Slim Phatty CV mod 1 volt /octave

Post by Colonel Monk » Sun Aug 16, 2020 9:17 am


I've had a phatty for quite a while. First a Lil Phatty, then I sold that and got a Slim. I'm in the process of building a sorta junkyard Eurorack to integrate all my synth gear into one sorta semimodular unit, and expand from there. I want to be able to use my Slim in there as well.

I have read, that the pitch CV doesn't track well with other 1 volt / octave gear, and that the Slim can be modded to fix this.

Anyone here done this? Any idea what it costs? Did it work?

Any other comments on whether or not this is doable?


Colonel Monk

Slim Phatty, Foogertron 7000: Low Pass, Ring Mod, Phaser, 104z Delay, ClusterFlux, Bass MuRF, FreqBox, CP-251
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Re: Slim Phatty CV mod 1 volt /octave

Post by till » Sun Aug 16, 2020 11:27 am

If the Slim Phatty is getting to sharp when controlled external, try to put a potentiometer in line the CV to reduce the ingoing voltage a bit. Try to use a attenuator module for this before doing something else Set it to zero attenuating and then lower it a tiny bit. If it is to flat, use some VCA or other module able to boost DC voltages. Again it is most likely only a tiny boost needed.

Most analog synths are built to send exactly 1 V/oct but receive them a bit lower than this, as reducing the ingoing CV a bit is easier than boosting it a bit.

Most likely we are talking here about about 10 mV/oct or less. So most cheap voltmeters won't show the value exactly, although giving a read-out with two or three digits after the decimal point.
keep on turning these Moog knobs

Prodigy * minimoog '79 * Voyager * MF102 * MF103 * MF104z * MP201 * Taurus 3 * Minitaur * Sub Phatty * MF105 * Minimoog 2017+ MUSE * One 16

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