Oran wrote:So, I'm modding a few more Monotrons and I think I'm interested in utilizing your new gate/pitch fix method you've outlined.... Masa's other method seems questionable to me as it sounds like it affects the LFO.
If you mean the method of adding a bipolar transistor to pull down pin 9 of IC2C, that fix should work in the same manner as mine. It's the same method with different implementation.
Have you (or anyone else, for that matter) physically tested this method yet?
Yes. My Monotron has the mod I sketched up. No problems.
If so, are there are side-effects? (e.g. Does the ribbon remain functional?, etc.)
The ribbon still functions as normal. Either the ribbon or the external input will gate the sound and both also retrigger the LFO. When there is no external input plugged-in, the Monotron operates as stock.
I'm still a bit confused about using an existing ("spare"??) part of the circuitry as a fix. Will this not affect anything else?
The Schmitt-trigger/inverter IC contains six identical circuits; only four are used in the Monotron. Two of the inverters have their inputs tied to VCC or ground and their outputs are unused. Making use of these inverters does not affect any other circuit.
When I have an effective gate/pitch fix enabled (even as simple as removing r11) am I correct in assuming that I do not need the additional pot as described in DinSync's schematic? Upon testing, this pot seems to only be necessary in the case that the gate is allowed to affect the pitch, in which case fine-tuning (e.g. calibration w Silent Way) of the cv pitch is necessary. With a fix in place it seems that the pot on the back of the Monotron is sufficient, and two separate pots seems like overkill.
You are partially correct. The pot on the back of the Monotron can be used to calibrate the scale factor. There are a couple of drawbacks. First, the pot on the back is less convenient, especially if you need to periodically adjust for temperature drift. Second, the pot on the back affects the scaling of the ribbon controller, so you will have to adjust it back and forth if you sometimes use the external input and sometimes the ribbon.
If you use Silent Way, you should not need the external pot. The software will calibrate the scale gain and offset automatically, gate-fix or not.