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Volume Pedal Questions – inc using as an Expression Pedal

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Volume Pedal Questions – inc using as an Expression Pedal

Postby S.Crow » Mon Apr 12, 2021 2:29 pm

Hi, I have an Ernie Ball VP JR 25K which they describe as being ‘for active signals’ so I suspect that it will impact the tone if using it with a guitar that doesn’t have active pickups.
Is there a simple and inexpensive way to overcome this?

I watched a Youtube video with Joshua at JHS Pedals over the weekend and he mentioned that you can use a Volume pedal as an expression pedal.
He mentioned that you need a particular type of cable to do this and he used a name that I couldn’t make out so what cable will I need?

Here is the video and it should start at the section where he talks about this. If not, there are links underneath the video which go straight to 06:28:
http://www.youtube.com/watch?v=6Ot9rhGgcyQ&t=6m28s
Thanks
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Re: Volume Pedal Questions – inc using as an Expression Pedal

Postby Martin Walker » Mon Apr 12, 2021 2:59 pm

Hi S.Crow!

To avoid an expression pedal changing the tone of your guitar you ideally need some sort of high impedance buffer amp first in the chain - many pedal FX will do this for you.

You then need a 1/4-inch stereo jack to twin jack SPLITTER cable, which for your purpose splits a stereo signal into send and return plugs to connect to an expression pedal input. Here's a typical one:

Image

https://www.amazon.co.uk/MainCore-Conve ... SPHG&psc=1


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Re: Volume Pedal Questions – inc using as an Expression Pedal

Postby Hugh Robjohns » Mon Apr 12, 2021 2:59 pm

S.Crow wrote:Hi, I have an Ernie Ball VP JR 25K which they describe as being ‘for active signals’ so I suspect that it will impact the tone if using it with a guitar that doesn’t have active pickups.

The pedal has a 25K Ohm pot in it, which would be fine for an electronic source -- guitars with active pickups, keyboards, etc -- but it would load down passive pickups far too much and suck the tone out (and level) of it!

Is there a simple and inexpensive way to overcome this?

Not directly... but you could use it as a volume pedal after an effects pedal and before the amp (instead of between the guitar and amp/FX pedal). This is because most effects pedals have electronic outputs that will be happy to drive a 25K pot.

I watched a Youtube video with Joshua at JHS Pedals over the weekend and he mentioned that you can use a Volume pedal as an expression pedal.

Yes... provided you use it to control something that offers that facility. An expression pedal is one used to adjust a control voltage for some other device rather than affecting the audio signal directly.

He mentioned that you need a particular type of cable to do this and he used a name that I couldn’t make out so what cable will I need?

A 'splitter cable' which has a TRS plug at one end, and two TS plugs at the other. It's a way of connecting a standard volume pedal's separate input and output sockets, to an effects unit that needs them to be wired between the tip and ring contacts of a TRS socket.
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Re: Volume Pedal Questions – inc using as an Expression Pedal

Postby Wonks » Mon Apr 12, 2021 3:13 pm

He said 'splitter cable' but it's also known as an 'insert lead'. It has a TRS (tip, ring, sleeve), jack on one end, which is split into two output cables. On one, the TS jack is connected T to T and S to S (no R connection) on the the TS jack, on the other lead, the TS jack is connected T to R and S to S (no T connection).

e.g. https://www.andertons.co.uk/andertons-p ... no-jack-1m

A 25k pot volume pedal is, as you mentioned, designed for active signals. Passive guitar volume pedals normally have 250k (pots or greater) in. As it works just like the volume pot in your guitar (but in addition to it), you really want a value that is similar or greater to the pot in your guitar.

The options are either to swap out the existing pot for a 250k or 500k pot, or else always use say a clean boost pedal before the volume pedal that you always keep turned on. Or it could be a pedal with an active buffer (not true bypass). But a boost pedal set for unity gain is probably the easiest and cheapest. That way the passive guitar sees the high impedance of the pedal, and isn't 'loaded' and dull sounding, whilst the pedal is driven from the active output of the pedal and is also 'happy'.

Expression pedals come in two basic types (sometimes selectable via different jack connections or a switch on the pedal), to suit the two types of expression output on synths and pedals.

One type of expression output needs to see a variable resistance, and uses a TS to TS cable, and only two of the three connections on the pot. This type needs the right value pot resistance to get full expression, so whilst some may want a 25k pot, others may need a 50k or 10k pot. So you'd need to refer to your device documentation as to what resistance is required here.

The other type of expression output uses the three connections on the pot as a voltage divider, with typically 5v being sent to one end of the pot, the other connected to 0v/ground and the output from the wiper (which the pedal position moves around the sweep of the pot) being the control signal back to the device.

So most dedicated expression pedals of this type use a TRS jack input, as will the output device, and a TRS to TRS (stereo) cable. But because some manufacturers put out the 5v on the T and get the signal back on the R, and others the 5v on the R and get the signal back on the T, there's often a switch to swap over the T and R connections on the pedal so that it works with both types. On the EB volume pedal, using the splitter/insert cable, you just have to swap over the jacks going into EB volume pedal if it doesn't work correctly.

Because it's working as a potential divider, the pot value rarely makes any difference to the pedal's operation.

Again, it helps to know what sort of expression output your pedal or keyboard requires.

One other thing to consider is the pot taper used. An expression pedal will almost always use a linear taper, but a volume pedal is likely to use a log taper pot, so that volume changes sound linear, and not all bunched up at one end of the pedal's travel. This may make for a harder to control level of expression if the volume pedal is used as an expression pedal. So it may be simpler to just get a dedicated expression pedal. This Moog one for TRS use is relatively cheap and is good quality. It also has that polarity reverse switch. https://www.andertons.co.uk/guitar-dept ... sion-pedal

For a TS expression pedal, you need to look at the device's manual and find a suitable resistance pedal (not always easy to determine as Yamaha probably just say use a Yamaha xyz... pedal, so some web searching is often called for).
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Re: Volume Pedal Questions – inc using as an Expression Pedal

Postby S.Crow » Tue Apr 20, 2021 7:30 pm

Thanks for all the replies. It’s been busier than I like so after reading the replies quickly I decided to wait until I had more time before replying.

I did wonder if I could use a pedal to reduce or remove the effect of using this volume pedal with my guitar so great to have that confirmed.
I did a brief test with these 3 configurations and noticed a difference:
1. Guitar – Looper – Mixer
2. Guitar – Volume Pedal - Looper – Mixer
3. Guitar – Drive Pedal - Volume Pedal - Looper – Mixer

Although I need to redo it with a more complex tone from the guitar to see a larger difference I suspect.
I may record all 3 and then analyse them to see the frequency content.

I ordered a volume pedal which came today as I’d like sometimes to be able to move away from all the pedals with a long lead but still use a volume pedal. In that scenario I don’t want to have the extra hassle of also needing a drive pedal. I’d either need to use a power supply for it or buy a new one that used batteries, neither of which appeal.

I’ll have to look into the expression pedal thing more to get my head fully around it.
I have a Morley expression pedal so will start with that and then see about utilising the Ernie Ball volume pedal for expression.
These will be used with mainly BOSS gear but also an Eventide H9.
Some fun little projects for when I finally have more free time.
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