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Author Topic: LFO Pitch knob issue  (Read 631 times)

kevinmoore73

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LFO Pitch knob issue
« on: November 24, 2012, 07:22:06 pm »
With the LFO off (mod wheel set to "LFOAmt" and all the way down), changes to the LFO Pitch knob affect the sound.  All the way up drops the pitch almost a semitone and all the way down raises the pitch most of a semitone.

The LFO Filter knob also has some effect when the LFO is off, but its effect isn't as pronounced as the Pich knob and it's harder to explain the sound.

Edit:  Here is a video demonstration:  http://youtu.be/tdzlll-EkNw
« Last Edit: November 24, 2012, 08:48:38 pm by kevinmoore73 »

Bruno@arturia

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Re: LFO Pitch knob issue
« Reply #1 on: November 26, 2012, 10:10:18 am »
Hi,
this is a know issue of MiniBrute. When the Mod wheel controls the LFO amount, and is set to 0, moving the LFO Pitch amount will detune the machine. It could be indeed up to almost 1/2 semiton in the worst case. Every machine should have this behavior, but more or less noticeable.

When the Modwheel is used on the LFO, the LFO goes through a simple VCA that does have a DC output offset, even if the amount is 0.
Unfortunately, this offset is different on each machine. This is why their is a trimmer on the PCB that is supposed to reduce this problem.

But it turns out that the offset changes with temperature. So the trimmer has been set so that, at a classic 20C to 25C room temperature, after a 30 minutes warm-up, the de-pitch due to LFO amount should become smaller. At startup the detune should be worst than after a long enough warm up.

Can you please tell me what is the observed detune after a minimum 30 minutes warmup?
Mod wheel set to LFO, mod wheel position 0, measure pitch with LFO Pitch amount at center position, then measure pitch again with LFO Pitch amount set to max.

Let me know
Bruno
Arturia Hardware

kevinmoore73

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Re: LFO Pitch knob issue
« Reply #2 on: November 26, 2012, 02:01:09 pm »
The behavior I described above is after several hours of use.  It's about 80 cents flat with mod wheel set to control LFO, mod wheel at zero, and pitch knob all the way up.

 

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