EA Tremolo speed switch

[Supernaut_]

Hi guys!

I'm gonna build a GuitarPCB EA Tremolo v3 kit, which is basically the same circuit as the GGG's Improved EA trem. I've been researching modifications and stumbled upon this brilliant half speed switch by Dragonfly:

https://www.aronnelson.com/gallery/main.php/v/DRAGONFLY-LAYOUTS_0/The-Mod-Zone-_/EA_rate_mod.gif.html

This got me thinking. If I replace the stock 1uF capacitor trio with three 0.5 uF caps it should double the tremolo speed, right? And if I then install a 3-way on-off-on DPDT switch with a 50k resistor on one side and a 25k resistor on the other, this should basically give me the option to switch between double speed, regular speed, and half speed (relative to the stock 1uF circuit with a 100k pot). Is there any reason this wouldn't work?

And the switch should be placed between R15 and the speed pot (P3) in this schematic?:

https://guitarpcb.com/wp-content/uploads/2018/06/BD_EA-Tremelo-v3.pdf

Cheers!

[GGBB]

If I replace the stock 1uF capacitor trio with three 0.5 uF caps it should double the tremolo speed, right?

Yes. At least on paper - real world results might not be that satisfying at higher speeds (not enough depth to hear it?). Try it.

And if I then install a 3-way on-off-on DPDT switch with a 50k resistor on one side and a 25k resistor on the other, this should basically give me the option to switch between double speed, regular speed, and half speed (relative to the stock 1uF circuit with a 100k pot). Is there any reason this wouldn't work?

And the switch should be placed between R15 and the speed pot (P3) in this schematic?:

https://guitarpcb.com/wp-content/uploads/2018/06/BD_EA-Tremelo-v3.pdf

If you substitute a DPDT on-off-on for the DPDT on-on in the "1/2-speed mod" diagram, you would be breaking the connection in the center-off position - so the tremolo wouldn't work. (If you mean some other wiring - please post a diagram.)

Also note that the speed control is anti-logarithmic, so to cut speed in half from max you need to increase resistance by a much smaller amount than half the pot value - math says ~10k based on 100k pot.

[Supernaut_]

Thanks for the reply GGBB!

The thought had crossed my mind that the 0.5 uF caps might be too fast for the circuit to handle. I remember reading in some other thread that 0.68 uF caps had yielded nice results for higher speeds. I'll probably put in a trio of those plus the simple half speed switch.

That's a good point about the rev log pot and the required resistor value, thanks for pointing that out. I guess Dragonfly's resistor value was based on using a linear 100k speed pot.

Actually, could I just replace R15 with an on-on DPDT switch, with the standard R15 value 1k resistor wired to one side (to replace the jumper in Dragonfly's switch diagram) and the half speed 10k resistor to the other?

[GGBB]

Actually, could I just replace R15 with an on-on DPDT switch, with the standard R15 value 1k resistor wired to one side (to replace the jumper in Dragonfly's switch diagram) and the half speed 10k resistor to the other?

Yes - and you can do the same thing with an SPDT on-on:

[Supernaut_]

Awesome, thanks a lot GGBB! I'll be sure to give this one a go in the near future.

I'm also planning on using the original 1M linear depth pot, jumpering R11 and replacing R10 with a 500k trim pot. This should probably give enough tweaking room to dial in the right amount of "choppiness".