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Topic: analog.Read() of a POT: Is 10 bit enough for guitar audio tone sculpting? (Read 185 times) previous topic - next topic

Stoopalini

I'm currently working on a project to add MIDI preset recall capability to a guitar effect pedal which doesn't have MIDI.  You can see my thread on the project here, if interested in the full story: Virtual, variable resistors, with saved presets recallable by MIDI

I have a general proof of concept up and running for storing and recalling potentiometer readings, but of course, since I'm using a Nano, I'm limited to 1024 values when reading the analog POT due to the Nano being 10 bit.  It also seems I may be limited to 1024 values for the digital POTs I plan to interface with the pedal's existing circuitry; Although I'll admit I haven't searched to see if higher resolution digiPOTs are out there yet, mainly because the reading from the analog is limited to 1024 anyway.  I'm guessing they may exist.


So my question is: Should I be concerned about this from a tone perspective?  The effect pedal is a really great sounding pedal, and it essentially simulates a preamp for running a guitar signal direct to a PA system, without needing to mic up an amp. 

The audio signal inside the pedal does route through the two potentiometers I am looking to replace with DigiPOTs for automated control.

The existing analog POTs in the pedal are 100k pots and I assume the sensitivity on them is far above 1024 values just due to the analog nature of a POT. 

The usability of this effect pedal is that a small turn on the POT, like 30 minutes (or 15*), does have an impact on the guitar's tone.  Using the 100k resistor value, and dividing by 1024 resolution, tells me the Nano's reading will be in step increments of about 97.6ohms. 

So essentially the effect pedal will go from having almost infinite adjustment capability, to having jumps of 97.6 OHMs between each of the 1024 settings. 

Obviously the best answer is "finish up the project and see how it sounds", which I am working towards;  but if folks who have experience in this kind of thing tell me 97 OHM jumps will definitely be obvious, then I'll start looking into a 12bit, or higher, external DAC for the Nano to interface with over SPI (or similar) protocol. 

Thanks for any input/advice, it's greatly appreciated! 

Grumpy_Mike

Quote
So essentially the effect pedal will go from having almost infinite adjustment capability, to having jumps of 97.6 OHMs between each of the 1024 settings.
So a normal pot has an adjustment range of about 270o so that you get 270 / 1024 = 0.263o equivalent mechanical resolution. How good are you at twisting a knob? Can you reset it to within a degree even?

Stoopalini

Good point ... the math doesn't lie.  I suppose the answer is it should give me plenty of adjustment.  I hadn't thought about it from the 270* rotation perspective.


Oh, and just for the record:

How good are you at twisting a knob?
I'm really, really good at twisting knobs ... dare I say the BEST knob twister?!

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