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  #1  
Old 06-07-2011, 08:55 AM
Dan Dan is offline
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Join Date: Jun 2011
Location: Czech Republic
Posts: 5
Post Wah MPA control

Hi, i have made MPA module for controlling 100k Wah pot in Cry Baby.

I want the wah on as soon as I move the expression pedal upward, and off when I return it to full down position.
Contrariwise to domct203 : "MPA Replacing Wah potentiometer."

I use this :
Potentiometer 0 Power-Up Position=01 controller CC#2
Logic Output 0 Power-Up State "on" (5V) controller CC#2 (for switching relay)

F0 00 01 5D 01

00 02 02
00 02 15
00 02 16
00 02 17

00

10 02
10 15
10 16
10 17
10 18
10 19
10 1A
10 1B

01 7F 7F 7F

01 00 00 00 00 00 00 00

F7

I'm afraid, the Logic output can change the status only by meeting the 64/65 value, not from another value.
Can I anyway to achieve it?

Other thing is audio behavior of MPA, i send a short sample of it.
It makes "- some sort of artifact from the "steps" in the digital pots- ".
It makes the wah unusable.
The Mpa pot replaces the wah pot, connection with shielded cable.
I must admit, I have no totally shielded circuit. I try another shielding.

Thanks for answer.

Dan
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  #2  
Old 06-13-2011, 05:11 PM
John's Avatar
John John is offline
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Posts: 3,007
Default

Hi Dan, welcome.

Let me know how the filtering works for the digital potentiometer artifacts. I'll send a PM to discuss your requirement for the logic behavior.
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  #3  
Old 06-18-2011, 06:28 AM
Dan Dan is offline
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Join Date: Jun 2011
Location: Czech Republic
Posts: 5
Default MPA audio behavior

Hi, I must say, no kind of shielding helps to remove digital artifacts.
It is probably dependent on the use in the audio circuit, in Dunlop's Cry Baby the MPA cannot be used.
The only solution I see is a pair of LED/LDR optocoupler and it is more complicated.

Dan
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Old 06-21-2011, 06:37 PM
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John John is offline
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Default

Dan, sorry to hear that the digipot is still leaving artifacts in the audio signal.

You might try contacting domct203 to see what approach he used. (I realize it might not apply to your particular circuit.)

For anyone else reading this, I'm referring to this thread:

http://forum.highlyliquid.com/showthread.php?t=384
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