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La Crosse, WI
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Hello all! Brand newbie here, waiting to get my first arduino in the mail but pretty psyched to get started. Anyway I am planning on controlling my guitar amp, a Vox Mini 3, specifically I want it to act like a multi channel amp by presetting a couple of trim pots in three seperate circuits to control the onboard amp modeling potentiometer (10k 11 position), gain potentiometer (10k linear), tone potentiometer (10k linear), and be able to bypass and use the amp functions as normal. I was thinking I could make a footswitch with three buttons tied low with five volt going to my controller when pressed that would activate the seperate circuits. By putting the modeling selector in the middle of its range and connecting a 10k trimmer in parallel I was able to select the amp model that I wanted, and could do the same with tone and gain pots. My question is with the two 10k pots in parallel like that wouldn't the resistance be roughly 5k and will the controller agree with that resistance? Seems like I read somewhere that they are pretty particular about the impedence they see. Any help, direction, or ideas would be greatly appreciated! Thanks in advance! Jeff
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My question is with the two 10k pots in parallel like that wouldn't the resistance be roughly 5k and will the controller agree with that resistance?
Which controller? The Arduino will be OK with 5K resistors. Extremes like 100M cause some issues, but anything in the 2K to 50K range will work.
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La Crosse, WI
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I have a freeduino sb and a protoshield on the way. Was thinking of using DPDT relays to do the switching since the project will be mounted in the amplifier and power is not an issue. Would it be better to use ICs or something else for the switching tasks? Thanks again for any help! Jeff
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By putting the modeling selector in the middle of its range and connecting a 10k trimmer in parallel I was able to select the amp model that I wanted, and could do the same with tone and gain pots. My question is with the two 10k pots in parallel like that wouldn't the resistance be roughly 5k and will the controller agree with that resistance? Seems like I read somewhere that they are pretty particular about the impedence they see...

...Was thinking of using DPDT relays to do the switching
If you are using relays (and presumably a transistor or MOSFET to drive the relay), the Arduino will be isolated from the pots.   A relay is probably the "safest" way to go, because the relay contacts can handle AC signals, as well as DC, and you shouldn't have to worry about what the pots are doing or if there is audio or DC control signals going through them.

Adding trim pots in parallel with the existing pots is unpredictable.    Apparently it's working for you, but depending on the circuit you might risk damaging the Vox, especially if you turn the pots in opposite directions.  So...  I'd suggest you use the relay to switch-out the existing pot while switching-in the trim-pot.   A DPDT relay can do this if one end of the pot is grounded, be4cause you can leave teh ground connected on both pots and and you only need to switch the other two terminals.      The danger with this design is that there will probably be a "glitch" when the relay switches.   And, you might need an additional relay to mute the sound during switching.

If you get a couple of manual DPDT switches, you can experiment manually before you build & program the controller circuit.

 

 
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La Crosse, WI
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Thanks for the replies guys! Good ideas, I might just desolder the pots from the board and use leads to the relays, then from the normally closed poles back to the pots, that way I can avoid running everything in parallel. Thanks again. Jeff
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