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Tell me about Expression pedals...

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Tell me about Expression pedals...

Postby jaminem » Tue Oct 29, 2019 3:29 pm

Hi all, got a few pedals recently that have Expression pedal inputs and it has peaked my curiosity.
Would appreciate your knowledge on whats good and whats not?
Things to look out for, things to avoid
Is it useful to have a volume pedal and expression built into one, like an FV-500 for example?
High Impedance, low impedance...?

Just looking for some advice and education...

Thanks
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Re: Tell me about Expression pedals...

Postby Martin Walker » Tue Oct 29, 2019 5:37 pm

Hi jaminem!

At the risk of overloading your brain, you could always have a read of my FAQ entitled "Expression Pedals not generating the full range of MIDI Data":

https://www.soundonsound.com/forum/view ... t=800#8037

As it mentions (among all the other info) "Most pedals contain a 10K ohm or similar value pot, with the bottom end of the pot connected to the screen of the cable, and the top and slider either connected to the tip and ring of its captive TRS-wired jack lead or the other way round (top to wiper and slider to tip)."


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Re: Tell me about Expression pedals...

Postby Wonks » Tue Oct 29, 2019 6:08 pm

There are two types of expression pedal connection.

The more common one is just a pot, wired as a potential divider (like a guitar volume pot), so there's normally nothing normally that clever about them. Though some pedals have a manually adjustable pot that's used to set a minimum value. So the exact pot value doesn't matter too much, as it will always give a control voltage back. No audio going through the pedal, it's just there to give a voltage signal back.

With a volume pedal, one end of the pot is the guitar input signal, the other end of the pot is the common/through ground connection and the wiper connects to the output signal jack.

With an expression pedal, there's normally only one TRS jack connection and one end of the pot is a fixed voltage output from the main pedal (or synth), the other end of the pot ground connection and the wiper is the variable voltage level signal going back.

The other type of expression pedal uses a two-wire TS jack cable and the pot acts as a variable resistor, forming an external part of a bridge circuit that's within the main pedal or synth.

So it's important to find out what sort of expression pedal is required.

The Boss FV-500H pedal (and the 500L) in expression pedal mode is the first type of expression pedal and uses a TRS cable. You can't use it for volume and expression at the
same time, so to me, you'd be better off using a dedicated expression pedal, which normally has a smaller footprint so is far more pedalboard friendly.

Because the main type of expression pedal is a potential divider, that type will work over a wide range of impedances.

Personally, for a TRS connection, I'd go for a Moog EP3 expression pedal, which is half the size and price of the FV-500, and has that minimum output level adjustment, which could be very useful with some pedals if you want to use the full pedal sweep. It also has a polarity selector switch if you need to swap the T and R connections over for the expression pedal to work correctly.
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Re: Tell me about Expression pedals...

Postby The Elf » Tue Oct 29, 2019 6:13 pm

You do have to be very careful about the connections inside the pedals and the value of the pot. Although Mission pedals are ludicrously expensive, it is worth having a look at their catalogue of pedals to get an appreciation of the range of values.

Interestingly I have three Yamaha FC7 pedals (built like weapons of war), and two of the three I had to mod to get the wiring correct - the third worked out of the box... :crazy:
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Re: Tell me about Expression pedals...

Postby blinddrew » Tue Oct 29, 2019 10:41 pm

And just a bit of buyers remorse from me, I have an FV50H (not the 500) and it's pretty disappointing. As you back the volume you get everything, most, still most, a bit less, nothing. Really not very smooth at all and the last quarter of the action does pretty much nothing.
So don't be tempted to economise! :)
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Re: Tell me about Expression pedals...

Postby The Elf » Tue Oct 29, 2019 10:54 pm

blinddrew wrote:And just a bit of buyers remorse from me, I have an FV50H (not the 500) and it's pretty disappointing. As you back the volume you get everything, most, still most, a bit less, nothing. Really not very smooth at all and the last quarter of the action does pretty much nothing.
Try a quick jury-rig to switch the connections around. I've had that kind of behaviour and fixed it with an adapter cable, or a bit of internal re-wiring.
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Re: Tell me about Expression pedals...

Postby Studio Support Gnome » Tue Oct 29, 2019 10:58 pm

I quite like my Zoom Expression/control/volume pedal....

I have it hooked in to my Rocktron Midi pedal, and set up to do various things on various patches....

Zoom also made the most insane expression pedal of all time , on my old MultiFX unit (the G9.2tt which I still have ) , the large pedal on the right hand side could have it's top surface "unlocked" from the supporting structure... and move laterally through about 30 degrees, giving you both vertical travel and lateral travel so you could control two discrete effect parameters , from one pedal, at the same time...

that thing is awesome.... I am pondering using it instead of the rocktron...
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Re: Tell me about Expression pedals...

Postby Wonks » Tue Oct 29, 2019 11:00 pm

Sounds very much like the pot's got the wrong taper for volume, Drew.
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Re: Tell me about Expression pedals...

Postby blinddrew » Tue Oct 29, 2019 11:08 pm

I keep meaning to fish it out and have a decent look at it but...
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Re: Tell me about Expression pedals...

Postby Wonks » Tue Oct 29, 2019 11:32 pm

Just do it!
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Re: Tell me about Expression pedals...

Postby blinddrew » Tue Oct 29, 2019 11:40 pm

it's on the list!
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Re: Tell me about Expression pedals...

Postby Hugh Robjohns » Tue Oct 29, 2019 11:51 pm

I think the Elf might have hit the mark with the connections the wrong way around for the device you're plugging it into. That, or the pot value is much too high for the device.
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Re: Tell me about Expression pedals...

Postby blinddrew » Tue Oct 29, 2019 11:58 pm

It's in between the compressor (yellow) and the organ pedal:
Image
Shouldn't be anything funny going on there.
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Re: Tell me about Expression pedals...

Postby jaminem » Wed Oct 30, 2019 4:41 pm

Thanks all, i'll take a look at the Moog!

and avoid the FV50
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Re: Tell me about Expression pedals...

Postby BJG145 » Wed Oct 30, 2019 5:40 pm

jaminem wrote:Thanks all, i'll take a look at the Moog!

Good luck! (Incidentally it's "piqued" - it comes from old French "pique" meaning a prick or sting; ultimately the same root as "pike", the long pointy thing. Not the fish.)

Image

*edit*

Do you know what, it is the fish, too! Fascinating.

:boring:
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Re: Tell me about Expression pedals...

Postby jaminem » Wed Oct 30, 2019 6:10 pm

BJG145 wrote:
jaminem wrote:Thanks all, i'll take a look at the Moog!

Good luck! (Incidentally it's "piqued" - it comes from old French "pique" meaning a prick or sting; ultimately the same root as "pike", the long pointy thing. Not the fish.)

Image

*edit*

Do you know what, it is the fish, too! Fascinating.

:boring:

Ah yes, as in RMS Pique right?
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Re: Tell me about Expression pedals...

Postby Wonks » Wed Oct 30, 2019 6:25 pm

blinddrew wrote:It's in between the compressor (yellow) and the organ pedal:
Shouldn't be anything funny going on there.

You said 'organ'. Fnarr, fnarr! :D
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Re: Tell me about Expression pedals...

Postby BJG145 » Wed Oct 30, 2019 6:36 pm

jaminem wrote:Ah yes, as in RMS Pique right?

That was a mail ship, yes...? Got torpedoed during the war.

Image
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Re: Tell me about Expression pedals...

Postby Wonks » Wed Oct 30, 2019 6:50 pm

I can see a trumpet player, a drummer, a double bass player and a saxophonist still on the deck. In other words...

A band on ship.
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Re: Tell me about Expression pedals...

Postby ManFromGlass » Wed Oct 30, 2019 6:52 pm

I recently bought the Tensor pedal which is a new-ish generation pedal. My old Roland EV-5 worked perfectly with it. I haven’t delved too deeply into the controllability of the Tensor (it is extensive) but right now the pedal is controlling the amount of pedal effect applied to the guitar sound.
Great fun this controller pedal thing.
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