EA Tremolo - anyone have mod schematics?

[Chris oej]

Hi,

I want to build an EA Tremolo - a staple favourite of the DIY community. I'd like to add the below mods:

1. Flashing LED timed with the LFO - shouldn't be too hard, i've seen lots on this.
2. A wave shape control - to switch between sine and square - i've seen this http://www.diystompboxes.com/smfforum/index.php?topic=91444.msg817035#msg817035 but there's no schematic.
3. A tap tempo delay - this might be a bit tricky!

Does anyone have any schematics with any of the above features?

Thanks

[boogietone]

Hi,

I want to build an EA Tremolo - a staple favourite of the DIY community. I'd like to add the below mods:

1. Flashing LED timed with the LFO - shouldn't be too hard, i've seen lots on this.

Replace the 15K resistor (R8) between the 9V power and the LFO with a 10K resistor and LED in series. The LED goes on the LFO side of the resistor. This is shown in the GG mods document.

2. A wave shape control - to switch between sine and square - i've seen this http://www.diystompboxes.com/smfforum/index.php?topic=91444.msg817035#msg817035 but there's no schematic.

I don't think that you get a real square wave out of this. Basically, this mod changes R6 from a fixed 1K2 resistor to a arrangement that varies from 1K2 to ~93K. I have never seen a schem with this mod but I think the description in the post would have the the "To shape pot" lead wired to pot lug 1 and then pot lug 3 to ground, though I may have that backwards. I think of R6 as a minimum depth control. Larger values equal a greater minimum depth while smaller values the opposite.

3. A tap tempo delay - this might be a bit tricky!

Does anyone have any schematics with any of the above features?

Thanks

[GGBB]

I don't think that you get a real square wave out of this. ... I think of R6 as a minimum depth control. Larger values equal a greater minimum depth while smaller values the opposite.

I was wondering about that myself.  I assumed R19 controlled the minimum depth since it is beside the depth pot - does R6 do the same thing in a different way?  I have just built one and came up with my own implementation for making it sound choppier by increasing depth (I replaced R7 with a pot on a switch) but what I would really like is to make the wave squarer if that is actually possible in this circuit.  I used perfboard so I can easily make mods.  Is the R6 mod just affecting depth or does it actually affect wave shape?

[Chris oej]

I finally got round to building it. using the below schematic, i added the LED and 10k resistor in place of R8 and replaced R19 with an On/On DPDT switch with a 120k resistor on one side and a 1M on the other, this controls the minimum depth. I'm not sure that the 1m gives a true square wave, but it does make the sound very choppy which is what i'm after - all in all a massive success - thanks for all the help.


http://www.generalguitargadgets.com/pdf/ggg_eat_sc_improved.pdf?phpMyAdmin=4a28f86a515b7883e7bc35a68d4e7b6d&phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

[GGBB]

I was also quite pleased with the depth increase I was able to get - quite choppy indeed.  You might want to try lowering R11 a bit or replacing it with a 1K trimpot - I was able to squeeze a little bit more speed out of it which sounds great with the new max depth.