Expression Pedals and CV Sequencers

[Vhailor]

Hi, all!

This is a copy 'n' paste of the initial post of a thread which I started on TGP earlier today. It's been there all day and no one has replied. And there's some pretty talkative people there. But not for that thread!

I'm hoping someone can help me with this.

Thanks in advance!

Some pedals have cv inputs, and to these one may attach not only foot controllers, but also cv sequencers such as the EHX 8-Step Program. This allows one to sync the associated parameter with the track which you're recording on your DAW.


Some pedals have, not inputs labeled "cv", but labeled as expression pedal inputs. This is a different matter. Sometimes.


According to CrazyNightOwl on https://www.thegearpage.net/board/index ... l.1113705/* some expression inputs will accept cv voltages but others are based on resistance. Ryan, who is Mr Dr Scientist, informed me of the same via email.


Now, my goal here is to be able to sync the resistance-based-expression-input-controlled parameters to the rest of the track.


However, I basically know nothing about this subject except that I have been having big big fun using an EHX 8-Stepper with pedals sporting a cv input.


I'd like to find an "expression pedal sequencer" that would be, essentially, an EHX 8-Stepper but meant for resistance-based exp inputs.


Does such a thing exist? Is it possible to modify the output of the 8-Stepper to be compatible with the resistance-based exp inputs? These could be exceedingly stupid questions; I simply don't know.


Any "input" would be greatly appreciated!

* Full quote follows:

Possibly but it would depend a lot on the pedal in question and there appear to be few if any standards. The best thing would be to connect a normal EP first and measure the voltages that are present on the EP's potentiometer. Even then some deduction may be required to determine if it's a true "potentiometric (3-wire, voltage divider)" system or some other approach based more on the pot resistance (2-wire, rheostat, current based).

For one example I know for sure the Boomerang pedals are voltage controlled (0 to +3.3VDC on the tip) so you would want to use a voltage divider to scale the 0-5VDC range down to 0-3.3VDC. The input resistance is extremely high (~1Gohm) so the divider could use high resistor values and not change the "curve" (although CCs are usually linear I think so it might even improve things to warp it a bit towards a logarithmic, in your case it might already be logarithmic ). You would also want to use a TRS plug and leave the ring unconnected so as not to short the reference voltage supplied for normal passive EP pots.

Anyway, it could also work on many other pedals depending on their design but you would have to inquire or investigate on a one-by-one basis.

[DRodriguez]

So vactrols are the most common way I know of to convert cv to resistance. Look into some circuits based on that.

[Pepe]

Copilot fx Broadcast? Adam is currently building one for me with two EXP outputs.

[oldangelmidnight]

The EHX 8-Step isn't just CV, it's also meant to work in place of a standard expression pedal.
What are you trying to control with it?

[Vhailor]

So vactrols are the most common way I know of to convert cv to resistance. Look into some circuits based on that.

I would need an off-the-self solution or something that someone could build for me very cheap! I have no electronics or soldering skills whatsoever.

Copilot fx Broadcast? Adam is currently building one for me with two EXP outputs.

I actually have a Copilot Broadcast. However, while it may run resistance-based expression inputs, it will not accept midi clock or, apparently, cv input so I don't see how this will let me sync-to-track. (Mine is modded for an expression control for the ration functio.)

This will let my 8-Stepper run a resistance-based expression input? I see that I'm a-gonna have to read up about this thing. (I bought that because it seemed that it would eventually be useful but to be honest, my understanding of its function, purpose, and possible utility was, and is, well...)

Dunno how much Copilot would want to mod my Broadcast in order for it to accept either cv voltage or midi clock. I think that maybe I might email him about it.

The EHX 8-Step isn't just CV, it's also meant to work in place of a standard expression pedal.
What are you trying to control with it?

Dr Scientist Tremolessence. I've exchanged some emails with Ryan there (and he seems to be a very nice and more importantly very patient guy!). It's from him that I know that the exp inputs on the Trem are resistance-based.

As for the 8-Stepper taking the place of a standard expression pedal, I don't see how but if you could explain to me, I would be very, very grateful. I have just started using the 8-Stepper and have not read the whole manual, so certainly there's stuff in there I don't know and don't even suspect.

But http://www.ehx.com/products/8-step-program says

Compatible expression inputs must accept a voltage source as the controlling signal. The expression input should also allow for an expression pedal TRS plug with the following connections: Sleeve = Heel, Ring = Toe, Tip = Wiper. The expression voltage present on the Ring of the TRS plug sets the maximum range of the controlling signal; this Ring voltage must be between 2VDC and 9VDC.

So I don't know if that's going to work.... But if I'm missing something (easily possible!) then I'll be glad to know!

[Pepe]

I actually have a Copilot Broadcast. However, while it may run resistance-based expression inputs, it will not accept midi clock or, apparently, cv input so I don't see how this will let me sync-to-track. (Mine is modded for an expression control for the ration functio.)

The current Broadcast models have CV input and output.

[Vhailor]

I actually have a Copilot Broadcast. However, while it may run resistance-based expression inputs, it will not accept midi clock or, apparently, cv input so I don't see how this will let me sync-to-track. (Mine is modded for an expression control for the ration function.)

The current Broadcast models have CV input and output.

I have looked and am looking again at the Copilot website, and the manual, and I don't see anything about cv in. I'm going to email Adam just to be sure, though.

Do you know when Copilot started adding the cv input to the Broadcasts?

[Pepe]

I don't know that. I stumbled over Adam's Broadcast a few weeks ago and it was exactly what I was looking for to control the filters of my old KORG 800DV synthesizer and other instruments/pedals.

[Vhailor]

NO problem. I have already emailed Adam and I'm pretty confident that I'll get an answer soon. And then we'll see! Hopefully you are right about it, though.

[Pepe]

Maybe he can modify your already existing model?

[autopilot]

yes, the stock 4 knob / 1 footswitch broadcast doesnt have a cv input, just a exp out and a cv out jacks.

the cv in can be added by request, it is a custom option since it will depend inwhat the user want to control (ratio, manual sweep -bypassing the lfo-, range, wave, etc).

the stock broadbands and bandwidths does have a cv in but doesnt have lfo's

[Vhailor]

yes, the stock 4 knob / 1 footswitch broadcast doesnt have a cv input, just a exp out and a cv out jacks. ...
the stock broadbands and bandwidths does have a cv in but doesnt have lfo's

Man, it's always something, ain't it!

I assume, by the way, that that was you who sent me the email; thank you very much for you replies both there and here.

But, once again, to make sure that I correctly understand this matter which is way, way beyond any area of expertise that I have ever inhabited, the Broadcast will properly feed a "resistance-based" expression input of the sort that won't work with the 8-Stepper's 0v-5v ouput, correct?

Thank you again!

[autopilot]

the broadcast have 2 outputs one that is a resistance (exp out) and the cv out which outputs a voltage 0-5v (which is meant to sync with the broadband/bandwidth to increase the number of outs)

[Vhailor]

Beautiful!

Thank you!


Oh and thanks to everyone who participated in this thread!

[DRodriguez]

http://www.synthrotek.com/vac-pak-cv-to ... ers-dream/

That kit comes in at under $20. $5 for just the pcb if you or a builder wants to source their own parts.

And it can be daisy chained for multiple outs.