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Topic: How to digitally control analog circuits. (Read 1 time) previous topic - next topic


Nov 13, 2008, 08:00 pm Last Edit: Nov 13, 2008, 08:01 pm by AlphaBeta Reason: 1
Hello! I am on my way to building a guitar tube amplifier but I am stuck on the how to digitally control pots at the same time as the user can control them. I would very much like to not have to read a pot, then set a digital pot accordingly so what I wonder is this: Is there such a thing as a digital pot with a conventional chaft with an endless turn-radius. [so that when user tweaks he/she tweaks from where pos is in program, to ensure smooth tweaking on stage]

I am looking for something like the pots on this mixer: http://www.synthtopia.com/synth_review/Behringer/images/BCR2000_big.jpg

All info that can help digitally control analog circuits. Typically resistors, capacitors and transistors.

Sorry for asking, but I can not find the pot that I am after.

Maybe I have to make one myself. Rotary encoder with a ring of leds around it.  Hmmm..


Nov 16, 2008, 06:05 am Last Edit: Nov 16, 2008, 06:10 am by AlphaBeta Reason: 1
Does no one have any ideas on how to recieve analog user input, that it could be possible to digitally override that input.

Anyone know if anyone sells some motorized faders?

This is the best I've seen so far http://www.goldmine-elec-products.com/prodinfo.asp?number=G9962


This kit is designed to allow you to retro-fit a stereo so that you can  control the volume using a remote. Not saying the kit is what you want, but it shows a motor+pot in one part.



Use Rotary Encoders with 2phase output, then XOR the new value with the old one.  You can tell which way the pot is turning and then just increment whatever value its linked to.  I don't think anybody sells the rotary encoders with LED rings, but I could be wrong.

I think you need to use control voltages and PWM output (or some kind of DAC) if you want to control analog circuit bits.  Look at compressors / tremolo or synth stuff (VCAs).


BTW Dick Smith site URLs are munted, here's a URL from the "email this link" link:




Hello, I aim to control large currents and voltages, and I have not yet succeeded(?) to find a digital potentiometer that suits my needs.

I think I have setteled for motorized faders. The alto motorized pots are too slow (with one expensive exception, something with 'audio' in its name) but the faders seems to keep up rather good.

An additional criteria has been given me, and it is that all of the audio signal path has to be analog. (this rules out encoder+digitalpot)

I think I will go ahead and buy some motorized faders, anyone knows of a good source for such things? [that ships worldwide or within europe]


Dec 29, 2008, 01:50 am Last Edit: Dec 29, 2008, 01:51 am by crimony Reason: 1
> An additional criteria has been given me, and it is that all of the audio
> signal path has to be analog. (this rules out encoder+digitalpot)

Not really true, digital pots generally have a fully analogue signal path with switched precision resistors, it's the control logic which is digital. The signal path would be no different to a stepped-attenuator style volume control (such as the ALPS 27 - very popular with audiophiles), the difference is electronic control rather than a manual switch.


hello : ) how did you get on with your project?

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