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LFO rate encoder (not a pot) response

LFO rate encoder (not a pot) response
« on: October 07, 2018, 03:14:13 AM »

I have a doubt about the nature of the LFO RATE control: is it a pot or a digital encoder? Looks like the first, but its response is actually like the second, and that frustrates me quite a lot.

I like to “perform” with the LFO rate but it’s basically impossible to make fine adjustments: turning the knob always results in an initial “big” jump followed by a smoother response. Consequently, in order to find a specific rate frequency, the only option is to make big sweeps that hopefully land on the desired value, because approaching it with small steps won’t work.

However, since it’s (seemingly) a digital encoder, maybe the issue has been already addressed in the newest software update? I’m using the 1.2 version.


Re: LFO rate encoder (not a pot) response
« Reply #1 on: October 07, 2018, 11:38:15 AM »
Hi and welcome.

The speed control knob of the LFO is indeed a potentiometer, but the values it changes are digital in nature (the varying resistance is measured and converted into digital values by an ADC) with a limited resolution (maximum of 256 steps). Moreover, the response is not linear but exponential. So it can give the impression that the knob is an encoder especially towards the end of the travel where each value changes the speed dramatically, whereas in lower values it's more precise.

I've never understood why DSI (now Sequential) elected to have such an exponential response, and such low resolution, which renders the last part of the travel almost useless for any kind of precisely controlled FM.

It should have been linear all the way and with enough resolution as to allow very precise frequency control over the whole range, not with a very limited resolution of only 256 possible values (8 bits). We're in 2018, I would have expected a resolution of at least 65536 values (16 bits) for such an important parameter (as well as for the filter cutoff frequency manual control too).

All pots on any modern synth should have an ADC capable of 16 bits resolution for emulating real analog controls correctly. The technology exists and is really inexpensive to implement.

So, to answer your question: that's the way the synth is designed unfortunately.
« Last Edit: October 07, 2018, 11:40:01 AM by AlainHubert »
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