CV "duplicator" + "converter"?

[nasta]

I have a WMD Protostar that has an ENV OUT jack, which sends out a 0-5V CV signal based on the envelope of the input.

I wish to be able to take this CV signal, duplicate it (so I have multiple identical CV signals), and convert them into outputs that can feed into expression inputs on pedals.

any ideas on how I should go about accomplishing this (schematics would be a huge help)?

[PRR]

Welcome!

Normally we just Y one output to several inputs. CV output is low-Z, CV input is high-Z, loading is minimal. Have you tried that?

[idy]

There are different situations...most expression pedals are varying resistance, some use a 10k pot for example. So for that you would need to convert the CV into a resistance, maybe an LED shining on a LDR.

But yes, it the pedals all require CV in, you are probably good to go. Some odd arrangements might require some buffer(s), some pedals have less than optimal engineering....To tell you more we would need to know what each pedals you want to do this with.

[nasta]

Welcome!

Normally we just Y one output to several inputs. CV output is low-Z, CV input is high-Z, loading is minimal. Have you tried that?

I have read about this, but the only pedals/rack units I own (currently) that have expression jacks are my Lexicon Vortex and my EHX HOG - both of which are either too rare or too expensive to replace, if I screw them up somehow by feeding way too much voltage into them.

I could build myself another PT2399 delay to test this out (its the only pedal I've built thus far) - but I figured if I were to build something, might as well build the actual CV duplicator+converter.

There are different situations...most expression pedals are varying resistance, some use a 10k pot for example. So for that you would need to convert the CV into a resistance, maybe an LED shining on a LDR.

But yes, it the pedals all require CV in, you are probably good to go. Some odd arrangements might require some buffer(s), some pedals have less than optimal engineering....To tell you more we would need to know what each pedals you want to do this with.

for now I only want to do this with my Lexicon Vortex and my EHX HOG - but I was planning to build a solution that could feed 5 different pedals' expression inputs.

[ElectricDruid]

Welcome Nasta!

Neither the Vortex or the HOG actually have "official" CV inputs. They're both expecting a Tip-Ring-Sleeve expression pedal. I snipped the following from the user manuals:





Now, on modern processor-based pedals like these, an expression pedal input is usually just a pot wired as a voltage divider feeding an ADC input on the processor. E.g. the three connections are +V and Ground coming from the pedal to the ends of the pot, and the final voltage going from the pot wiper back to the pedal. If you measure the +V, you can find what CV range the processor is expecting and then feed it a voltage directly rather than using an expression pedal.

A *typical* arrangement is ground on the sleeve, +V on the ring, and the wiper to the tip, and the Hog2 manual suggests this is what the EHX pedal is expecting. So put a TRS lead into the expression jack, and then test the voltage from the ring to the sleeve at the open end of the lead.

Hope this helps!
Tom

PS: I'm guessing 3.3V for both!!

[nasta]

PS: I'm guessing 3.3V for both!!

and you're correct on that haha!

so what does this mean? can I just connect straight from the ENV OUT of my Protostar to the expression inputs on either of my HOG or Vortex?
and how about connecting to both at the same time? how would I go about doing that?

[ElectricDruid]

PS: I'm guessing 3.3V for both!!

and you're correct on that haha!

so what does this mean? can I just connect straight from the ENV OUT of my Protostar to the expression inputs on either of my HOG or Vortex?

No, not a good idea if the Protostar outputs 0-5V and the pedals are expecting 0-3.3V input, although I'd expect the input is protected with a series resistor just in case. Still, we might not want to find out it isn't the hard way.

You'd need to reduce the level to 2/3rds, so (for example) a 10K/20K resistor pair would make a divider to do that. Once you've got the level right, you need to send it to the right place.

It's *almost* certainly the case that the +V in the two pedals is protected with a series resistor, since someone plugging a mono jack into the expression pedal socket is bound to happen sooner or later. So you *should* be able to plug the output from your divider straight into the pedal with a mono lead. Think about what happens - CV goes to tip, sleeve connects to sleeve, so we have a ground connection, but the socket's ring +V is also shorted to ground - this is ok if there's a 1K (say) series resistor, since the resistor just pulls a few mA and nothing else happens.

If you want to be really safe, make yourself a special TRS lead with the CV to the tip, the sleeve connected to ground, and the ring unconnected.

and how about connecting to both at the same time? how would I go about doing that?

You should be able to send the same signal to both pedals without needing any extra splitter circuitry - just add more leads!