EA Tremolo mod with clipping diodes?

[Ben Lyman]

Any reason this would be bad? Has it already been done before?
I boarded the GGG "Improved EA Tremolo" and I really like it: http://www.generalguitargadgets.com/pdf/ggg_eat_sc_improved.pdf
Tons of volume boost if needed, so much that I thought, why not try a pair of 1n914 to ground after C2. I also put a 1nF parallel to the diodes, just seemed nicer.
Do a couple diodes have problems getting along with R12 25K volume pot?
Here, check it out

[Ben Lyman]

No comments yet, eh. I'm gonna go for it if nobody can tell me why not 
In fact, here's the update: 3 diodes!!! Yes, 3 diodes plus a 1nF cap. Two diodes are series and one loner is parallel along with the cap. It sounds great, I believe this is asymmetrical clipping, right?
It is responsive to the volume knob on the guitar or light picking, brings the volume up a teeny tiny bit and makes a milder overdrive sound that I think really compliments the tremolo.
Of course, all this would be on a toggle so the pedal is not always grungy. I'll try to make another sample vid later.

[Kipper4]

The proof is in the pudding is what we say round here.
I can't see any problems with the diode addition but I'm no EE, I'm more your stick it n the breadboard and see how it sounds.
Hopefully someone more knowledgable than I will advise you. Until such time carry on.
If you have a scope stick it on it to observe the clipping and see if it's symmetric or asymmetrical.

[Pojo]

Like kipper said. If sounds good go for it!

If it were me, I'd only be concerned with loss of output since the diodes are clipping the signal without any further amplification to provide makeup gain. 2 1n940s on one side and one on the other will allow about 1.8v pp max signal to the volume pot. High enough I would think, but if it were me I would put the circuit in a switched true bypass loop to do an A/B test and make sure you have at least unity gain when engaged.

[Ben Lyman]

Yer, kipper. That's what i'm thinking. No scope yet but hopefully some day i'll get there.
Pojo, thanks for the heads up. One of the things that the EA Trem seems to be famous for is the fact that it doubles as a clean boost, and boy does it ever. So much so, that adding a few diodes hardly affects it at all. I think I will just put all 3 diodes and 1n right on a SPST mini toggle and put it in there.
Here's a vid with the new "lighter" gristle grinder asymmetrical tone. First i'll try to show how the pedal can be used as a clean boost and OD just by turning off the depth knob.

[midwayfair]

I'd be more worried about losing depth to the effect than raw output.

The EA tremolo rhythmically BOOSTS the signal. The lowest spot in the swing is 1x gain. The highest spot is, well, lots more, depending on exactly what the FET is like.

The volume control in it cuts the volume at the output.

So if you clip the output to .6v p-p, that's probably not much above -- and possibly less than -- the original signal strength. When the tremolo boosts the signal whatsoever, you get more clipping. So not much wiggle there.

If it sounds good and does what you want, go for it. If you want distortion along with a typical tremolo effect, though, there might be a better way to go about it.

[Ben Lyman]

I'd be more worried about losing depth to the effect...

Dang! I knew it was too good to be true!

If it sounds good and does what you want, go for it.

Yes, I think I probably will 

If you want distortion along with a typical tremolo effect, though, there might be a better way to go about it.

That's kinda what I figured all along but... this is just too easy. As I tried to show in my vid, it is like 3 pedals in one:
1) a clean boost
2) a dirty boost
3) a tremolo
4) a dirty tremolo

even if the dirty trem feature isn't as deep, oh well it still has those other options. With 3 diodes the distortion is just light enough that I don't think it needs any more knobs for gain and stuff. Maybe it's just a gimmick but for how many parts it takes to build it, I think it's worth throwing it together. After I complete it, I will test it with the band and report back.
Thanks Jon, I always appreciate your expert opinions! 

[Transmogrifox]

The stock EA trem I have always thought is a relatively subtle tremolo anyway.  From your recorded samples I don't sense that you're losing much with the diodes engaged.  The tremolo effect pushes it in and out of clipping, which is a nice effect of its own.  Another thing you could do for an experiment is to put a resistor in series with your diodes to soften up the clipping a little bit.  There are several variations on that theme.

If you want more depth there is a simple mod for the typical EA circuit.  Basically you replace R6 (1k2) with a transistor configured as a constant current  source.  You can look at my rEAgenerated Tremolo schematic for ideas (Q2, R6 and some kind of bias).  You will want to keep the gain of the stock EA and volume control on the output when using it to drive clipping diodes.  Q2 and R6 are the "secret sauce" for getting more depth out of the EA trem.

I like the name "Gristelo" 

[Ben Lyman]

Thanks T-Fox, the rEAgenerated looks like a winner, I will have to take a closer look at it after I finish this one.
I have already started building it and, like you said, pushing in and out of clipping is kinda a cool effect itself.

[thermionix]

Pushing in and out of clipping - if you think about it that's what a lot of amp trems end up doing, especially when they're cranked up.  Maybe even more especially when you're swinging the power tube bias.

[Ben Lyman]

Finished last night. I love it, reminds me of a vibro-champ amp.

[chuckd666]

Damn that thing does Gimme Shelter well.

[Kipper4]

Good job Ben. I love it.

[duck_arse]

paint it black, you devil. it sounds real good. did you (and how) get enough range from the rate pot? and no winky led, that's a rare eatrem indeed.

[Ben Lyman]

Ya, if only I could do Gimme Shelter half as good as the pedal!!! 

Thanks guys, it really captures the old "cranked champ vibe" with it's light OD and choppy trem tone.
I like "Gristelo" but I'm also thinking maybe "The Pocket Champ"

Duck, I am happy with the range of speeds, I used the same parts that the GGG schematic called for.
My depth pot is A500K with a 510K across lugs 1&3 but I don't think that should've affected the rate...

I have a new theory about winky LEDs... they confuse me when I am jamming out with me bros, making' me think pedals are on when I don't want them on...
making' me think they are on when they are off but I want them on...     
No more blinkers for me from here on out... So it is written! So shall it be!

Here's an easy layout that fits in a 125B with (underside) board mounted pots, 1590B if you don't need room for the OD switch (under the board, too tall for me to squeeze)
3x 1N914 diodes and a 1nF cap are soldered right to my SPST with a wire to ground and a wire to the junction of 470nF output cap+A25K volume pot.
Look around, choose your own ground:


mirror image of traces


Double check your components before soldering

[duck_arse]

I hate to do this to you now, ben, but - there is an error on the ggg circuit, and it turns up over and over and over. you only need one cap between the input buffer Q and the booster Q. we all know that the total capacitance is always less than the lowest value in series, so you should ditch the 10uF.

and you could always mess w/ the winky so it changes colour when on, or stays off when bypassed.

[Ben Lyman]

Thanks Duck, better late than never! I remember looking at that days ago and wondering about it.
Oh well, I will ditch it on the next one.

I like the idea of the blinking light that goes off completely when bypassed... that would work for me 

[duck_arse]

easy done, connect the 47k clr to the led K and to the oscillator Q collector, then switch +9V to the led A with the bypass switch.

whoosh-ka. there are other ways, but not this simple.

[Ben Lyman]

Sounds cool Duck, thanks. Do you think this LED drawing current can affect the depth and/or rate in any way?

[Cozybuilder]

If Duck's method gives problems, you might try adding a transistor and cap, taking the input to the transistor base from the collector of Q3 like below: