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Expression Pedal Recommendations?

Postby BWC » Mon May 17, 2021 6:04 pm

It would be plugged in to one of the controller inputs of an IK Multimedia AXE I/O interface, and would be primarily for wah / volume, though I could imagine other creative uses, so versatility is always welcome.

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Re: Expression Pedal Recommendations?

Postby IAA » Mon May 17, 2021 9:21 pm

I use these in my keyboard rigs https://www.andertons.co.uk/guitar-dept/guitar-pedals/volume-expression-pedals/moog-moogerfooger-ep3-expression-pedal

They just do the one thing they’re supposed to well. Have had one of them for at least 7 years + and it’s had some hammer! But still works great.
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Re: Expression Pedal Recommendations?

Postby Wonks » Mon May 17, 2021 9:47 pm

The AXE I/O manual doesn't specify what sort of expression pedal is required apart from 'will work with any 1/4" TRS expression pedal', which I think is rather poor. Does the fixed voltage go out on the tip and the signal come back on the ring, or the fixed voltage go out on the ring and the signal come back on the tip? What is the maximum and minimum pot resistance that it will work with?

Whilst some pedals (like the Moogerfooger one) have a switch so that it can work in both modes, not all expression pedals do, and if you get the wrong one, then it won't work properly (or you have to rewire the cable to suit, which isn't great if you can't solder).

Another vote for the Moog pedal. I have one and although it hasn't had much use it's been 100% reliable and is well constructed. The minimum output pot control is also a useful feature.
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Re: Expression Pedal Recommendations?

Postby Folderol » Mon May 17, 2021 9:59 pm

I've no idea how they're designed these days, but the best ever that I came across had a lamp and an LDR. The pedal worked a vane between them. Beautifully smooth, with no pot to wear out. This was in the 1960s and was specific for a lugable simple organ :)
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Re: Expression Pedal Recommendations?

Postby Wonks » Mon May 17, 2021 10:20 pm

But I expect that LDR was a CdS device. RoHS rules mean they can't be used in new equipment because of the cadmium. Which is why I need to finish off replacing the noisy add-on tremolo board in my 68 Custom Deluxe Reverb amp with the lamp/LDR 'roach' they fit in the US.
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Re: Expression Pedal Recommendations?

Postby Wonks » Mon May 17, 2021 10:24 pm

And they are just pots, typically 25k, 50k or 100k, wired as potential dividers. Sometimes with a second pot wired as a variable resistor to provide a non-zero minimum setting facility.
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Re: Expression Pedal Recommendations?

Postby Folderol » Mon May 17, 2021 11:14 pm

Thanks Wonks. Pretty much as I suspected.
Incidentally, you can still get LDRs from RS (prolly Farnell too). I expect they'd work quite well with a yellow or green LED
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Re: Expression Pedal Recommendations?

Postby Hugh Robjohns » Mon May 17, 2021 11:38 pm

I like the Yamaha FC7. The pedal angle range can be configured for sitting or standing positions, and there is an adjustable spring-return 0-10 degree 'overpress' action if required for emphasis 'stabs' which can be handy. It has a 50k pot and the wiring obviously suits Yamaha keyboards, but I've not had any problems with any of the things I've plugged it into so far.
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Re: Expression Pedal Recommendations?

Postby BWC » Tue May 18, 2021 12:56 am

The Moog certainly looks like a solid choice. The other one that caught my eye while browsing is the Yamaha that Hugh likes, and for exactly those reasons.

Wonks wrote:The AXE I/O manual...

What I saw in the manual was a little different, but not really any more useful or detailed. I suspect, in keeping with the overall design philosophy of the thing, it's able to cope with as many scenarios as possible, and offers software control of curves, and ranges, and whatnot. For the record, a little soldering is not a problem for me, though my lazy side objects.


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Re: Expression Pedal Recommendations?

Postby Wonks » Tue May 18, 2021 7:20 am

Folderol wrote:Thanks Wonks. Pretty much as I suspected.
Incidentally, you can still get LDRs from RS (prolly Farnell too). I expect they'd work quite well with a yellow or green LED

It’s like 60/40 solder. You can still get it and use it for repair work but can’t use it commercially any more.

I’ve bought a pre-assembled ‘roach’, and have already removed the add-on board (I fail to see how they couldn’t design a circuit that didn’t make an audible tick every cycle). I just need to fit the ‘roach’.
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Re: Expression Pedal Recommendations?

Postby Wonks » Tue May 18, 2021 12:10 pm

Apologies for the thread hijack but as I started I may as well finish...

Just soldered the 'roach in' and I now have an almost noiseless trem/vibrato. There's still a very faint pulse in the background, but its far quieter than anything I could get with the add-on board, and replacing the circuity driver valve may make it even quieter still. The add-on board had a trim pot to minimise the pulsing noise, but even the best adjustment couldn't make it silent. When playing, the noise got hidden, but when you stopped, back it came. It's now fully useable.

This will be the case in most of the Fender reissue amps built after RoHS came into effect in 2006, including the 65 Deluxe Reverb, or any other Fender amp that uses a LDR trem/vib circuit. And it's a pretty simple fix to replace the add in board with the lamp+LDR 'roach' and it will cost less about £10 for a pre-assembled 'roach'.
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Re: Expression Pedal Recommendations?

Postby BWC » Tue May 18, 2021 1:52 pm

Wonks wrote:Apologies for the thread hijack...

Eh, these things happen. I'd think that there'd be a modern, fully compliant, optical expression pedal on the market, but I haven't come across one. Anyone know of such a thing?
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Re: Expression Pedal Recommendations?

Postby Wonks » Tue May 18, 2021 2:34 pm

I don't know of any. The fact that it's an expression pedal means that you don't get the audio path going through it, just a control voltage, so if the pot did become slightly scratchy, you wouldn't hear it in the same way as you would as if it was a pure volume pedal with audio going through it.

A pot-based expression potential divider pedal can work with any extra-low DC voltage level likely to be thrown at it, say from 15v dc down to millivolts (though 9v and 5v are more likely). An optical pedal may need to be built for a specific input voltage, or else ignore the provided input voltage completely and have its own selectable output voltage range.

And optical volume pedals like the Morley 20/20 volume pedal are expensive (more so in the UK than the US), so I'd expect an optical expression pedal (if anyone made one) to be similar. If you've got a mid-price keyboard and want three expression pedals, by the time you've got three optical ones, you could have spent the best part of the cost of the keyboard again. Pot-based expression pedals are certainly far more affordable, and most can be DIY repaired by replacing the pot.

Using a splitter cable (TRS to 2 x TS) it should be possible to use a basic optical volume pedal as an expression pedal with a TRS style expression connection (provided the volume pedal doesn't have any DC blocking capacitors in the circuit). Whichever of the TS jacks provides the constant voltage output, then that goes in the input to the pedal and the other TS jack goes into the output of the volume pedal.

Any more complex optical pedal with boost functions is likely to have DC blocking capacitors, so your DC voltage will never get through. I've read on the web that the Morley 20/20 volume pedal can be used as an expression pedal, so that indicates that there aren't any DC blocking capacitors, but I can't guarantee it. It's also expensive and large and needs its own power supply, so will take up a lot of real estate on a pedalboard. Also, I once had a Morley Power Wah, and I couldn't get on with the range of pedal angle; it was all wrong for my feet and I had aching ankles after 30 seconds or so. On an angled pedalboard I'd imagine it would be even harder to use. But YMMV.
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Re: Expression Pedal Recommendations?

Postby Folderol » Tue May 18, 2021 2:55 pm

Just to clarify, the one I was referring to had the LDR in the signal path. There weren't any voltage controlled amplifiers in those days. The organ was populated entirely with discrete transistors - mostly germanium ones. If I remember right, the only silicon ones were in the 12 (yes 12) master oscillators, so the instrument was semi free-phase.
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Re: Expression Pedal Recommendations?

Postby BWC » Tue May 18, 2021 3:23 pm

Yeah, that's what I thought, not worth it when a potentiometer will do well enough, but you never know, I've seen crazier things brought to market.

So, I think I might prefer the Yamaha to the Moog, but looking again, it looks like the Moog has the advantage of being easier to keep out the dust, and hair, and such. Hard to be sure from pictures, any thoughts?
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