EA Tremolo Schematic: Tell Me Your Mods!

[railhead]

I'm thinking about tossing together an EA Tremolo just for kicks, so I built a basic schematic of the "Improved" version. So check out the schem below, and if you've built this little guy, let me know any of your component/value changes.

[jayp5150]

I built the one at ROG http://runoffgroove.com/eatremolo.html

The only changes I made were a lower value R19 on your schematic for more choppiness at max depth (47k, I think), and I used a trimpot for the volume.

I like it the way it is, otherwise. It's a great circuit.

I haven't built the one shown above, though. I think the only diff is the newer Mosfet input stage, isn't it?

[fuzzo]

you make me think, the mine doesn't work since one year

I've the sound (boosted when the volume knob is at max) but not the tremolo.

For the mod, I thinks you can add leds to see the rate or speed. See on GGG pdf project.

[railhead]

Yeah, the input stage is different, and I forgot about the blinking LED.

I'd like to toss a tap-tempo in there, just to make it easier to adjust speed in a live situation between songs (and during songs). I know taps aren't perfect in this analog circuit, but I'd rather use a tap to set tempo -- and have to adjust it every so often -- as opposed to manually turning a knob until I match rhythm.

[fuzzo]

to adjust the speed or the rate you can add a external expression pedal. I think you cannot add a tap tempo, or you must do somthing more complex than this tremolo.

[plankspank]

I just built the one @ ROG also. (It has a MOSFET for the 1st tranny). I love the sound, very vintage, quiet, lots of volume boost if you need it.

[neil411]

I did the GGG Boost Only Switch mod and installed it in an old Teisco-made archtop that I refurbed. It gives me a nice on-board tremolo with the added function of a basic pre-amp. The GFS pickups I used a little on the low-output side, so the pre-amp comes in handy.

One of the switches is a 3PDT mini-switch - one pole is the effect, one pole is true bypass, and the third pole disconnects the battery. The other mini-switch in the Boost Only switch. The battery is accessed through a holder on the edge of the guitar, next to the jack.

There is no status LED. I basically used that side of the mini-switch to disconnect the battery.

Works great, although it would take up too much space in a solid body guitar.





And just so you don't all yell at me for ruining an old vintage guitar, this is what I started with.

Bought it on eBay a few years ago, just a shell really:

[squidsquad]

I love the thing (mosfet input by Gez). 
I wired another 3/way stomp switch to choose between 2 speed pots. 
Fast or slow at the touch of a toe.
I play a lot of surf music...it is wonderful.

Warning: mosfets can vary a bit...some may sound better than others.
JFETS are even worse...can make the difference between *too soft* or even *too choppy* in the DEPTH department.
Ya may wanna socket & try a few.

[Processaurus]

Hi, as far as improvements on the original circuit, the most worthwhile I've found was the forum member Transmogrifox's rEAgenerated Tremolo, which uses a constant current source for R6 (in the original poster's schematic) rather than a resistor, which allows a vastly improved depth from this circuit.  Very worthwhile mod.  Also putting the volume control up front is a very good idea, because the headroom in this circuit is criminally low.

Here's my tricked out EA:

http://www.diystompboxes.com/smfforum/index.php?topic=36392.msg449154#msg449154
The pictures in the busted links:
http://www.aronnelson.com/gallery/main.php/v/Processaurus/project-leavings/album91/

Since then I added a square/chop switch, which opens the feedback resistor in the inverting amplifier I used to sum the two LFO's, making it into a comparator.  Also added a knob on the side to vary the DC level going to the non-inverting input of that opamp stage, which changes the duty cycle of the LFO.  It was terrible opening it back up and modding the circuit.

Transmogrifox has a version of his thing with the same idea, making a fast and slow LFO, with a knob to pan between them.

[railhead]

Thanks for the input -- I'm still deciding if I want to go with this, but if I do, I mashed the whole thing on a double-sided board that's only 49 x 30mm. Here it is actual size:

[Chris S]

Just to ask a quick and maybe dumb question what does JI JO and SG stand for (all earthed) and where does the L- (negative lead of the LED go) Ta!!

[railhead]

Just to ask a quick and maybe dumb question what does JI JO and SG stand for (all earthed) and where does the L- (negative lead of the LED go) Ta!!

Jack In, Jack Out, Switch Ground, and the LED- (on this board) goes to LA, which is traced to LB at the bottom edge, for a quick jump to switch lug 4.