EA Tremolo (GGG) with haxx complete! single LED for both modes, shape knob, etc

Started by thegnu, May 05, 2011, 02:10:55 PM

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thegnu

this thing took forever, so i'm posting some of the stuff i worked out, lest i get hit by a bus and have the fruits of my suffering lost to the world.  i did this on a GGG board, and used this schem (PDF)

number one, the pulsing LED on page 1 of the GGG mods pdf is drawn in the wrong polarity.  i just looked that the layout, wired it up, and then proceeded to waste a couple hours sorting it out why there was no tremolo.  it's one of the reasons the wiring isn't as neat as it was the first time i wired it up.

the second reason the wiring is nasty is i had to figure out the dual-mode LED (off/on with one switch, pulsing/steady for booster/trem), and fix some issues with the shape knob.

here are the pics:

http://imgur.com/a/bodgy

you can't really see, but the finish is barely transparent.  i took yellow enamel and clear enamel and sprayed the streams together onto it, so you can see a bit of the metal through the finish.  the knobs are volume, depth, shape, speed.  the switches are on/off and tremolo/booster.  the trem/boost switch replaces the shape knob with a 1k2 resistor (stock value) because when turned to higher resistance, the boost sounds nasty.  what actually enables the boost is shunting the depth control to ground.  here is my switch diagram:



the shape knob is a 250k lin pot with a 1k2 resistor across lugs 1 and 2, and a 150k resistor across lugs 1 and 3, giving me a range of about 1k2-95k.  i'm sure i'd be better off with a 100k pot, but i didn't have one. at about 1/4 turn from smooth, it crackles and the volume drops a bit. i'm assuming it's the weird load from the several resistors across the pot.  also, this is wired backwards for my taste.  the smooth tremolo is when the pot is maxed, choppy is when it's at minimum.  i do this all the time.  anyway, you just hook this deal up in place of R6.  i would recommend a 50k or 100k log pot with the 1k2 resistor across 2 and 3.

the depth knob, i used a 1M lin pot like the original, but left all the resistors like the GGG version.  i have a wide, wide range. super-sweet.

i used a 2n5089 for Q3, 2n5457 for Q2,Q4, and 2n5172 for Q1.  the BC109 was more brittle sounding than the 2n5172.

anyway, i love the damn thing.  the boost sounds good enough that the pedal was worth it, and the tremolo does everything i want except for nail that hummingbird/vox repeat percussion thing.

Chris oej