GGG EA Tremolo/'Blue Bird +' question (speed range)...

[rantony]

Hello everybody,

I'm planning to build a bias tremolo pedal based on the GGG EA Tremolo schematic. In the past, several boutique pedal manufacturers proposed products based on this schematic. The Outlaw Supply company was offering a pedal named the "Blue Bird". That pedal was a GGG EA Tremolo pedal equipped with a toggle switch to turn the tremolo off and just use the pedal as a boost. But there was also a model named the "Blue Bird Plus" that was an upgraded/deluxe version of the "Blue Bird".

Here is the description of the "Blue Bird Plus" that I found (thanks to webarchive):

Same Great Blue Bird with a couple added features. First you have 2 rate control knobs. You pick which rate you are using via foot switch. Now you can have one rate nice and slow and when you want to pick up the tempo your second choosen rate is just a stomp away. A small blue led over each rate knob lets you know which you're on. I've also added a speed range switch to go from heart beat slow to machine gun.

Here is the only picture of the pedal that I could find:


I understand the idea of the "2 rate control knobs". But what about the "speed range switch"? What is it for? What does it consist of exactly? Does it affect the tremolo type (shape) ? or is it simply a switch that allows to bypass the rate potentiometers in order to provide rate "presets" by adding a circuit with resistors that have a fixed value?

If the mod is useful, I might want to add it to my project. However, I need to know what it does, and then, how to do it...

If you can be of any help, please let me know.

Thanks!

N.-B.: For reference purpose, here is the link to the GGG schematic:

http://www.generalguitargadgets.com/pdf/ggg_eat_sc_improved.pdf

[mcknib]

I think it'll be changing the 1u cap values around the LFO ie larger cap slower charge and discharge times smaller value faster charge and discharge times

There's some discussion on it here

https://www.diystompboxes.com/smfforum/index.php?topic=43175.0

[duck_arse]

search this here forum for phase shift oscillator - there is a thread or two will tell how and what.