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Mod wheel bug?

Polyphonic Analog Synthesizer

Mod wheel bug?

Postby Skuggasveinn » Tue Aug 06, 2019 7:50 pm

Everything works as intended with the mod wheel until I do extremely slow movements. Moving the mod wheel from it's starting position to max dosn't modulate anything if I do it very slowly.

Im on 1.1.0

Can anyone confirm this as a bug?
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Re: Mod wheel bug?

Postby Iaamusic » Wed Aug 07, 2019 10:21 am

Just tried it - not sure how slow you're going but I went verrrrry slow and it seems OK to me - have you seen if the % actually change whilst you do that on the LHC panel more page?
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Re: Mod wheel bug?

Postby Skuggasveinn » Thu Aug 08, 2019 5:47 am

Hey and thanks for the reply.

Yes, I just tried it looking at the percentage. Doing it slowly makes the % not move at all, and if I go from one position to another, and then do a quick movement, it jumps to that modulation. For example if I move from bottom (0%) to top (100%) and midway through do a quick motion, it jumps from 0% to 50%.

This makes the mod wheel unusable for me in many projects.

And by slowly I mean, perhaps going from 0% to 100% in 1 minute or less.
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Re: Mod wheel bug?

Postby till » Thu Aug 08, 2019 10:47 am

I just tried it here on my Moog One 16 with the firmware 1.1.0:
If I move the wheel very steady and reeeaaaallllllllyyyyy slow (about 90 secs from min to max), I can't hear a change in sound and the display shows no value change. But if I move just a tiny bit of way a little less slow, I get the jump to the actual position instantly.

But it takes some practise to move the wheel that slow and without tiny faster movements all the way from min to max.

So I guess the needed routine to filter of little variation of knobs caused by little fluctuations is also added to the modwheel. without thisThis is not happening when using external Modwheel data via MIDI.

The most likely explanation for this:
The knobs are all A/D converted in order to get their values to the digital display and into the digital memory.
And these knobs change their values randomly by slight temperature and feed in voltage. So in order not to produce a new value every time the multiplexed A/D scans the knobs (most likely 100 times per second or more often), you use some filtering based on the value change of a knob. Without such filtering, the MIDI output and the display would flicker changing data on all knobs many times per second.
If a knob does change just tiny bit (somewhere at the 8th or more bit), this change is not considered as done by moving the knob. So this value change will not be used further. But the value is stored to check against the value produced at the next scanning. So if you move a knob real slow, and the mod wheel is also a knob, it won't produce a change in value. But if you move it just a tiny bit mechanically more then the set filtering limit range allowed as unwanted shift, the value is considered to be used.

You can do this small moving on several synths easily if you are patient enough to move a knob real slow.

So this is not a bug. But Moog could change the way the filtering works, in order to see if there is a kind of longterm small change going on. And if this happens, set the logic to consider the change as one done by the user.
So the routing could check in the cycle of the A/D loop, to see if the value changed from the last A/D loop cycle and also, if the value differs from, let's say 2 secs before and 5 secs before more then a certain threshold value change. It is like this on the Voyager. There you can't move a knob to slow to be noticed by the synth. But you might have to turn it a bit too much, before the Voyager sees the change actual taking place. So setting the detune beating often resulted in unwanted movements a bit to much, befor ethe Voyager noticed the change. So Rudi Linhard, who programmed the Voyager software years ago, added later a mode, where you could tell the Voyager to react to a moved knob instantly while you press a button.
keep on turning these Moog knobs

Prodigy * Minimoog (1979) * Voyager * MF102 * MF103 * MF104z * MP201 * Taurus 3 * Minitaur * Sub Phatty * MF105 * Minimoog reissues with MUSEs * One
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Re: Mod wheel bug?

Postby Skuggasveinn » Thu Aug 08, 2019 11:03 am

Thanks for the reply. That is very interesting and I can confirm that using an external synth's mod wheel (sub 37) totally worked without any problems.
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