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  #1  
Old 06-30-2015, 04:08 PM
soundog soundog is offline
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Default Jitter Problem

I currently have a bunch of good quality pots wired up, all 5K values. Four are regular rotary pots, 10 are faders. I often get a flashing MIDI activity light when there is no pot movement, and when I check the MIDI output I am getting repeating output for some of the pots, with the data value varying by 1 or 2 values.

Often I can move the pots around to a certain position and the random activity stops, but the problem seems to be random and unpredictable.

I've read on the forum about others encountering this "jitter" problem with the Midi CPU, but haven't seen any definitive solution. Is there one? FYI, I'm running firmware V1.2A.

Last edited by soundog; 06-30-2015 at 04:12 PM.
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  #2  
Old 06-30-2015, 04:50 PM
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John John is offline
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Quote:
Originally Posted by soundog View Post
I currently have a bunch of good quality pots wired up, all 5K values. Four are regular rotary pots, 10 are faders. I often get a flashing MIDI activity light when there is no pot movement, and when I check the MIDI output I am getting repeating output for some of the pots, with the data value varying by 1 or 2 values.

Often I can move the pots around to a certain position and the random activity stops, but the problem seems to be random and unpredictable.

I've read on the forum about others encountering this "jitter" problem with the Midi CPU, but haven't seen any definitive solution. Is there one? FYI, I'm running firmware V1.2A.
Hi Soundog,

There are a few different approaches to the problem:

- You can tweak the "ADC Configuration" values for the MIDI CPU. Described in the user manual. This may have unwanted side-effects (might make the inputs less responsive).

- Add an electrolytic cap (try ~47uF to start) across Vreg and Gnd, wired directly to the terminals of each pot.

- Use a low-pass filter circuit (could be simple RC filter with a single resistor and cap for each analog line). All kinds of info on the web. Try starting with a smallish R (maybe 100 ohms) to keep the signal impedance low.

- If the analog signal wires to the MIDI CPU are long, it might help to shield them.

Last edited by John; 06-30-2015 at 04:52 PM.
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Old 06-30-2015, 07:25 PM
soundog soundog is offline
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I'll experiment with these solutions and report back...
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  #4  
Old 02-23-2016, 08:18 PM
soundog soundog is offline
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This turned out to be a failing slide potentiometer. It took all these months for it to worsen to the point that it became obvious what was causing the problem. Just replaced the pot and now no more "jitter" problem. All is good again.
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