Adding a 1/2 speed switch for vibrato pedal...how difficult?

[skiraly017]

Curious about adding a 1/2 footswitch to a homebrew vibrato pedal like Fulltone or Diaz. Anybody tried/done this? Any layout diagrams out there? Thanks for the help.

[R.G.]

The speed of an LFO is generally proportional to one or more resistors and one or more caps. The speed pot is generally the resistor and the caps are fixed. There are two ways - change the resistors or change the caps.

To get half speed, you usually double the speed cap(s)' value. This is simply switching in another of the same capacitance. It's easy with the triangle/integrator style LFO, and hard with a phase shift LFO like the EA Trem.

Another way I've never seen done, but which works pretty darn well is to change the speed pot to a dual speed pot, both sections half the original resistance, but put in series. Each section contributes half the "slowness". By shorting across one, the speed doubles.

I guess this is a way of saying that you have to know what you have before you can change it in any meaningful way.

[Steve C]

Another way I've never seen done, but which works pretty darn well is to change the speed pot to a dual speed pot, both sections half the original resistance, but put in series. Each section contributes half the "slowness". By shorting across one, the speed doubles.

This is what the 1/2 speed switch on the Supa-Trem does.

[KORGULL]

I don't know what pedal you're working on there, but I used the mod in the following link to create a half speed control on my EA Tremolo:
http://www.diystompboxes.com/sboxforum/viewtopic.php?t=29886&highlight=half+speed
Scroll down a bit to see the diagram for the half-speed switch.
I put in smaller value caps to enable faster speeds and then dropped in this switch so I could still have very slow speeds too.
I ended up using something like a 91K resistor instead of the 50K that is shown in Dragonfly's diagram - it just worked better with my pedal.

[nelson]

why go for just half speed? why not switch between any two speeds?


http://aronnelson.com/gallery/The-Mod-Zone-%21/DUAL_VOLUME


i am sure that mod could be applied to the rate knob on a vibrato pedal.

[skiraly017]

why go for just half speed? why not switch between any two speeds?


http://aronnelson.com/gallery/The-Mod-Zone-%21/DUAL_VOLUME


i am sure that mod could be applied to the rate knob on a vibrato pedal.

Could I also wire the Depth control to this switch and have dual rate and dual depth controls? ex - Volume, Rate 1, Depth 1, Rate 2, Depth 2.

[nelson]

if one lug goes to ground yeah. If two lugs of the pot are joined, join them, if one goes to v+ and one to ground a SPDT would be enough. Hard to say without looking at the schem, but yeah you can do it with any control.