Volume Pedal Control Curve

[Jason Stanfield]

I've experimented with a variety of expression pedals for use as volume controls, and the two consistent problems I face are:

 

1. They never bring the volume to absolute silence; and

2. The curve is very narrow ...

 

The first 25% of the travel does nothing, then over the next 25% the volume jumps up to full, then the remaining 50% does nothing. I have to treat the pedal very delicately when controlling volume, and for things like wah control it's virtually useless because of the narrow curve.

 

Brands of keyboards used -- Roland, Korg, Yamaha, Hammond

Brands of pedals used -- Roland, Yamaha, Hammond, Boss, M-Audio

 

I've also noticed that Boss and Ernie Ball inline pedals do the same thing.

 

The only one that works is the Hammond volume pedal, but even it doesn't go to absolute 0 for volume, plus its polarity makes it useless with Yamaha, Korg, et al.

 

What gives? Is there a different kind of pot that can be substituted for the one that's inside there? Is there another brand that offers a smoother, fuller curve from 0 - 100%, either control or inline?

[J. Dan]

CLONK

[JMcS]

With the Hammond instruments, turning the The Expression Minimum, Limit Low Freq. and Limit High Freq. settings to Off should allow the (any - assuming polarity etc. is correct) pedal to bring the volume to 0. It also reduces or eliminates the benefits of "Expression" and just raises/lowers the volume (I think, I haven't tried it).

[Bill Spencer]

Are you plugging this in to the synth's Pedal jack, or simply running the audio output through a volume pedal?

 

If the former, make sure the pot and wiring scheme meets their specs. I've had to change the pots in my pedals for different keyboards. Yamaha has different specs than Kurtz, for sure. Sometimes I've had to reverse the polarity, too. Get the true specs for your application, as well as the pedal you're using, then modify the pedal to suit, or buy the pedal from the mfgr. of the synth.

 

I use Fender Tone/Volume pedals and rewire them so I have two pedals in one- vertical axis is for Expression, Lateral is CC4- Foot. Different 'boards require different pots.

 

Once set up correctly, mine definitely go all the way to silent (except on the Kurz's KB3 mode, where they've set it up to act like a true B3, where the swell pedal doesn't completely mute the output), and the response is linear through the whole travel of the pedal. I use a dual-axis pedal on every keyboard.

 

Or, get a Pedal Controller box from MIDI solutions. They seem to work with just about any pot and wiring scheme, and can be customized as to the response curve, etc.

[JeffLearman]

Are you plugging this in to the synth's Pedal jack, or simply running the audio output through a volume pedal?

The former, or he'd have said "volume pedal" and not "expression pedal".

 

I've never understood why the pot value has to match anything, since it's a basic voltage divider circuit. Half of 250K ohms is half the voltage, just as half of 25K Ohms is half the voltage. Of course, audio versus linear taper matters.

 

What really confused me is recently I used the y-cable trick to use a guitar (Ernie Ball) volume pedal as an expression pedal. What I didn't understand is that it worked well* even when I reversed the leads.

 

The trick is, use a stereo Y cable (aka TRS insert cable) that splits TRS into two TS, one for "left" and one for "right". You plug those into the input and output of the passive guitar volume pedal. What I haven't figured out is why it doesn't matter whether I plug left into input and right into output, or vice versa.

 

*well = pretty well, but max travel wasn't quite 100%, probably 90%. I could live with that, just turn up drive a bit to compensate. This was the same regardless of how it was connected.

[JeffLearman]

Lack of absolute silence is intentional, on Hammond clones, because that's how a Hammond expression pedal works. If you watch the MIDI values, you should see 0 through 127. I didn't bother to plug the above into a computer to check the range, but I might this weekend.

 

The response curve seems reasonable to me, for the cases I've tried:

- cheap Kurz pedal (Fatar) into MR76 -> NIB4

- Kurz -> NE2

- Ernie Ball -> NE2

- Jimmy (BluesKeys) Roland VK8M

 

I'll admit it's the opposite of how the volume knob works on my Fender Blues Deluxe, where it changes dramatically from 1 to 3, and much slower after that. Not that I ever get to turn it past 2 any more.

[JeffLearman]

Well, I figured out why the volume pedal works when plugged either way. I also figured that unless there's an internal buffer resistor, wired the wrong way and pedal full up (at zero), it'd draw lots of current. So, it might be important to plug it in the right way, even though it sounds fine the wrong way!

[ITGITC]

Well, I figured out why the volume pedal works when plugged either way. I also figured that unless there's an internal buffer resistor, wired the wrong way and pedal full up (at zero), it'd draw lots of current. So, it might be important to plug it in the right way, even though it sounds fine the wrong way!

LearJeff, I speak for all of us here when I say...

 

THANKS for putting your life on the line for the intellectual advancement of keyboard players everywhere!

 

Better your life than ours.

 

 

 

 

[JeffLearman]