vox repeat percussion for bass

[bogey]

hi everyone,
after hearing mine, a bass playing pal of mine asked me to build him a VRP. as I don't play bass and can't test what i'm building to suit any particular set up I was wondering if anyone had any suggestions for changes/mods.

I was thinking maybe put the tone caps on a small daughter board............using sockets so I can swap them out....(values?)

I might also throw a simple one knob fuzz in there as a bonus..........(coloursound?)

any help that anyone can offer would be greatly appreciated.

cheers Bogey

[rocket88]

Haven't built me one yet, but it's on my list. I think it should be fine as is for bass, but you can always socket the input and output caps and try different values to see if it makes a difference in the amount of bass that comes through.

As far as a one knobbie. Any of them will do fine, but again you want to up the input and output caps. I built the batw one and it rips.

[nocentelli]

Did he try it out through your pedal? The stock VRP is very treble-y and bass-lite to my mind, although it's part of the charm of the effect on guitar. I enjoyed playing around with it after an sub octaver and a looper for electro-y baselines, but found the Earthquaker Hummingbird variation on the VRP allowed much more of a full range effect. You could do the Hummingbird, but with a bass control so he could dial it back for a thinner sound when desired.

[Travis]

With the Hummingbird I can always hear my signal faintly during the "off cycle" even with the depth pot at max. This annoys me because I like to strum during the off cycle to maximize the choppy effect

Have you found that the normal Vox RP (without depth pot) has less sound bleeding into the off cycle nocentelli?

I don't find the depth pot particularly useful anyway, so would happily ditch it in order to achieve full on-off depth. Everything else about the Hummingbird is great

[Pedalhead]

Have to agree. I built the Skippy Tremolo version and modded the in/out caps to be bassier and it's still not as bassy as my stock Colorsound Tremolo. Great effect though. Use heatsinks on the transistors if your'e using the 2N2646, one of mine overheated & blew.

[nocentelli]

Travis wrote

Have you found that the normal Vox RP (without depth pot) has less sound bleeding into the off cycle nocentelli?

I don't recall, I didn't build it so my experience was limited to the breadboard. The "thinning effect" was way too strong when engaging a fuzz pedal in front of it, so i didn't pursue it once I'd tried the hummingbird. I'm sure you could dial the depth higher if you mod it to remove the depth pot.

This is what I built, it's actually a hybrid with the JFET stage from the EQD but the oscillator and depth pot arrangement from the Skippy by Moosapotamus, using the 2N6027 PUT rather than the original UJT -



Depth works from very strong percussive pulse (a la VRP) to totally unaffected, fulsome bass response and minimal ticking.

[moid]

Without derailing the subject too much Nocentelli would you mind if I asked you how you use the two grounds on this pedal? I assume the Direct ground goes to the pedal power jack ground. Where does the other ground go? The answer might solve a problem I have on another pedal (a Devi Ever OK Fuzz) where I'm looking to create a ground that the board can attach to that is not connected to the power jack ground (I've got a 22K trimmer that has the board ground going to lug 3 and nothing on lug 1 and then a cable from lug 2 to the power jack ground). If no other pedal shares the same power supply I get a lovely distorted pseudo tremelo effect alongside the fuzz from using this trimmer, but as soon as another pedal shares the same daisy chain I lose that effect and I hope that if I could ground the board to something other than the power jack that might cure my lack of pseudo tremelo effect.... Dwarfcraft use this effect on the Super Soda Meiser on the Drone knob but I don't know what they did inside the pedal to make it work if other pedals are attached to the same power supply. Thanks! Also I've saved your diagram, I'd love a Vox Repeat Percussion to get some Spacemen 3 sounds with :)

[nocentelli]

I'm not sure it's a ground issue that is causing your lack of tremolo with a shared supply: It might be that the other pedals have a large electrolytic capacitor across the power rails (to reduce supply noise on the +9v getting into the audio), but your OK fuzz does not: Connecting the pedals to the shared supply would then allow the power filtering cap to eliminate the oscillation that caused that lovely trem sound. Easy way to check is to simply plug the OK in on it's own, get that tremolo happening, then add a large electro across the rails to see if it kills the trem. I only mention this because I recall someone (maybe Iviark) added polarity protection and power filtering to some other Devi device, and it killed the oscillation.

In the VRP layout, the idea is to ensure that the ground wire to the PUT oscillator is not the same length of copper that connects to audio ground: Both ground wires connect to the same spot (battery/power negative) but the connections are made via separate physical paths to attempt to minimise the charge-dumping of the oscillator bleeding into the audio via ground.

[bogey]

Thanks for the input guys,

Nocentelli: re my friend playing his bass through my VRP, No he didn't.....he just heard me playing and thought he'd like one because he doesn't have anything like that.

In my hastiness i'd already built the board and thought that maybe the tone caps could be a quick fix to make it more bass friendly.

I'll plod on regardless and see how things turn out.

Best Regards

Bogey

[moid]

Thanks Nocentelli :) By placing a large electrolytic across the power rails do you mean place the positive leg of the electrolytic on the power in strip of the board and the negative leg on the ground strip? If so I'll try this and report what happens!

[nocentelli]

moid wrote

Thanks Nocentelli :) By placing a large electrolytic across the power rails do you mean place the positive leg of the electrolytic on the power in strip of the board and the negative leg on the ground strip? If so I'll try this and report what happens!

Yes. Some oscillating fuzzes do their thing by inducing oscillation in the power supply, a large capacitor (47Uf?) with the positive leg on +9v, and the negative striped leg on ground will shunt AC in the power to ground.

[moid]

I've just tried this but no luck alas - it didn't do anything at all. I tried 10uF, 47uF and 100uF. I even tried putting them across the power and ground of the dc jack as well, but the tremelo effect is still present. It only goes away when I plug another pedal into the chain and have that pedal use the same power supply. Can you think of anything else I could try please? I guess if the worst comes to the worst I'll just buy another power supply and run that pedal from it on it's own - the effect is really lovely though, I'd like to add it to other fuzzes. Thanks for your help.