Ernie Ball VP Junior Tuner Pedal as Expression Pedal?

[Matt]

Hi all, new user and first post. A friend of mine was saying that any standard volume pedal can be used as an expression pedal when a TRS-Y cable is plugged into the input and output jacks of the volume pedal, since the volume pedal is basically a voltage sweep that is sent to the output. So my questions are:

1. Can this be done with the Ernie Ball VPJR Tuner pedal (assuming the TRS polarity is correct) into the Mastermind GT16?

Here are the specs from the manual:
Power Input: 5.5mm OD, 2.1mm Pin Jack, 9v-18v DC, center pin negative, 150 Ma minimum
Input & FX Return: 1/4" Mono Tip Sleeve Jack, 1M Ohm Input Impedance
Output & Effects Send: 1/4" Mono Tip Sleeve Jack, 1M Ohm Input Impedance

This would really be helpful if there's a way to "rig" this to work. I'd use the pedal for expression and run a regular guitar cable to the pedal input for the built in tuner. I'm literally out of room on my pedalboard with no room for even a small tuner, so a built-in tuner/pedal would be perfect.

Cheers,
Matt

 

[rjmmusic]

Here's some information on expression pedals, including how to connect a volume pedal:

What expression pedals can I use with Mastermind GT/LT/PBC?

The Mastermind GT, LT and PBC can use a variety of expression pedals. Any resistance value from 10k to 250k can be used. Pedal calibration is required for best results, especially for lower resistance pedals. Expression pedals are available i...

rjmmusic.freshdesk.com

The taper compensation numbers in the article are measured from a VP Jr

 

[Matt]

Ernie Ball description says it’s an ‘active’ volume pedal and your article says that active pedals don’t work. Do you know if there's a small gadget that can be inserted between the pedal and the GT that steps it down to passive or a custom cable that can do it? Wish there was a way to get around the active issue as this vol/tuner pedal would be a perfect solution for me.

 

[rjmmusic]

Ah, I didn't catch that part. I have a passive VP Jr here, I didn't know there was an active one. There's nothing you could add to the pedal to make it passive, it would have to be modified internally, and I'm not sure how difficult that would be.

 

[sw616]

I've done it with the passive VP Jr. before. It "works", but the uh... travel? sweep? curve/line? is crazy. As in it's not an even line, it's an exponential (or logarithmic, I forget which) curve, so barely any difference for a good part of the sweep, and then all the difference in the last part of the sweep.
So doable, but I don't recommend it. Probably better off going for the Dunlop ones that have a jack dedicated to use for expression, in addition to the regular passive in/out jacks for guitar.

 

[rjmmusic]

That's what the taper compensation is for, you can use that to correct for the curve.