Control Freak

[drolo]

I had assumed you could define the value of each pot in program. But then I have not really read the datasheet 

[Marshall Arts]

https://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&sqi=2&ved=0ahUKEwj4pbjJgPPMAhWHnRoKHQL1DCQQFggtMAA&url=http%3A%2F%2Fwww.analog.com%2Fmedia%2Fen%2Ftechnical-documentation%2Fdata-sheets%2FAD5204_5206.pdf&usg=AFQjCNEoBA7U_ZWFppEUZw6GZk30FVuLzQ&bvm=bv.122676328,d.d2s&cad=rja

Page 18 shows the different types :-(

[drolo]

ohhh ...

[Coda-effects]

By seeing this I am just wondering: did anyone used a digipot for tremolo applications instead of a LDR? (which are crazy expensive, just spent 10 euros for a simple VTL5C1)

Maybe it is harder to get square waves ? (is the digipot fast enough?)

[Marshall Arts]

By seeing this I am just wondering: did anyone used a digipot for tremolo applications instead of a LDR? (which are crazy expensive, just spent 10 euros for a simple VTL5C1)

Maybe it is harder to get square waves ? (is the digipot fast enough?)

Tried it with a triangle wave, works! No glitches, no zipper sound, no steps whatsoever. I agree with the ridiculous prices vor VTLs, I paid 15 € for two VTLs just to test this (and to find out, that it is really hard to realize...).

[Marshall Arts]

yep
http://missionengineering.com/?product=expressionator-2
a bit on the expensive side but it's a cool device

Had a good night sleep over this and think that I would miss some more aspects in that approach:

• I would like to be able to bypass a device (e.g. a Wah), when the respective channel is not chosen (ideally this behaviour is configurable in presets). This would be my normal use scenario to only use one device at a time and step through them (volume-vibe-wah-volume-vibe...) and have the others taken out of the fx loop. For the fancy stuff (stuck-wah-volume-swell), choose another preset.
  
• Know Morley wahs? You dont have a switch on them, they just turn on when you move the pedal. It always returns to the heel position though, so you cannot have a "stuck wah" with them (unless you stay on the pedal...). With a microcontroller, I could get the best of both worlds, e.g. switch off the wah, if the pedall has been in the heel position for more than 2 seconds. Change to a "staircase taper", when the pedal has been in the toe position for more than one second. Or have a preferred stuck wah sound on heel or toe position... endless possibilities!

[Marshall Arts]

Findings from tonight: Hooked up a foot pedal (10k lin) and controlled a 100k digipot (lin) with it. I calculated the output resistance of the digipot to work as a log taper. The digipot was used as a volume control straight between guitar and amp.

Good news: Even though there is some taper calculation involved, it's mighty fast. I don't sense latency. This gives hope!
Bad news: On fast moves, I hear (very little) steps. Actually, not even steps, more like static. Not sure if it is a lack of resolution or a general architectural issue (make-before-break or break-before-make). If the latter, we are out of luck. If the first, we can increase the resolution sufficiently with three digital pots (see article above). I will find out latest over the weekend...

[Marshall Arts]

Meanwhile: More Crazy Stuff (vca controlled wah), look at the options: Software, Presets, 30 Pages a Manual... FOR A WAH!!!! https://www.prostage.eu/free_download/manuals_audio/RemoteWahWah_Users_Manual.pdf

[Marshall Arts]

So, I've build a 16 bit pot with three (8 bit) digital pots. It works for tremolo and for manual/pedal control. I would like to increase the resolution of the manual/pedal reading to at least 14 bit (the arduino nano has only 10 bit) - probably by oversampling (more latency) or by an external ADC (more components).

My biggest problem currently is hiss/noise in the breadboard setup: Most annoying is a high beep (most likely coming from arduinos clock signal). I buffered all the digital pots with 100n and terminated the end of the clock line with 10k. The sound is dependant on the jumper wires position (so, if I move them, it gets better or worse). Any ideas how to fight this problem?