Improved EA Tremolo

[ampman50]

I've been thinking of building the Improved EA Tremolo from General Guitar Gadgets. I have one question concerning C1 and C9. These caps are in series with no resistors between them. It looks like I could eliminate C9, the 10 uf cap. Is there a reason for connecting them in series?

[petemoore]

  I'm not looking at the schematic.
  That circuit has been gone over with fine toothed combs a few times, built exactly as shown, it works great.

[davent]

Hello,

I'm guessing that C9 was part of the buffer (?) that was tacked onto the front end of the original schematic to yield the improved EA Tremolo. As such i would think that it's redundant and unnecessary as C1 and C9 in series are going to result in a capacitance ever so sligtly less then C1.

I haven't built the GGG version of the EA but have built the ROG version which is different again and am really pleased with it.  http://www.runoffgroove.com/eatremolo.html

Take care,
dave

[zyxwyvu]

Fake edit: it seems davent has posted almost exactly the same advice.

I can't think of any good reason to have those two caps in series. It looks like a JFET buffer was just pasted in, output cap included. It should be fine without C9.

As long as you're building an EA tremolo, why not build the one at runoffgroove? (http://runoffgroove.com/eatremolo.html)
It's more compact, and has more features. A useful mod, though, is to remove the volume pot, and instead replace the 1M bias resistor (to the left of Q1) with a 1MA pot for volume (lug 3 to input, 2 to Q1, 1 to the trimpot). I've built that and it works great.

[Mugshot]

As long as you're building an EA tremolo, why not build the one at runoffgroove? (http://runoffgroove.com/eatremolo.html)

It's more compact, and has more features. A useful mod, though, is to remove the volume pot, and instead replace the 1M bias resistor (to the left of Q1) with a 1MA pot for volume (lug 3 to input, 2 to Q1, 1 to the trimpot). I've built that and it works great.

resurrecting this thread!

with this mod, do you just take out the 0.1uF input cap altogether? sorry if i misread, but im thinking with a 1Meg pot for this the input gets shorted. is this similar to the gain control used in the gain control for the Fetzer Valve?

[zyxwyvu]

with this mod, do you just take out the 0.1uF input cap altogether? sorry if i misread, but im thinking with a 1Meg pot for this the input gets shorted. is this similar to the gain control used in the gain control for the Fetzer Valve?

No, you still need the input cap. The Fetzer valve is fine with no input cap because it is biased around ground. The EA Tremolo, on the other hand, is biased above ground (with the trimpot), so you need an input cap. In case it is not clear, the input cap should be connected to lug 3 of the volume pot - the setup is similar to the Fetzer valve, except instead of lug 1 going to ground, it goes to the bias trimpot.

[Mugshot]

with this mod, do you just take out the 0.1uF input cap altogether? sorry if i misread, but im thinking with a 1Meg pot for this the input gets shorted. is this similar to the gain control used in the gain control for the Fetzer Valve?

No, you still need the input cap. The Fetzer valve is fine with no input cap because it is biased around ground. The EA Tremolo, on the other hand, is biased above ground (with the trimpot), so you need an input cap. In case it is not clear, the input cap should be connected to lug 3 of the volume pot - the setup is similar to the Fetzer valve, except instead of lug 1 going to ground, it goes to the bias trimpot.

with the mod you suggested, there is a constant 1Meg resistance between the bias control and the point after the input cap, and lug 2 of the pot either moves closer to either points, am i right?

to bias trimmer <--------------[lug 1]
                                           >
                                           < [lug2]___________ to Q1 Gate
                                           >
                                           <
input ---||----------------------[lug 3]

[zyxwyvu]

with the mod you suggested, there is a constant 1Meg resistance between the bias control and the point after the input cap, and lug 2 of the pot either moves closer to either points, am i right?

to bias trimmer <--------------[lug 1]
                                           >
                                           < [lug2]___________ to Q1 Gate
                                           >
                                           <
input ---||----------------------[lug 3]

Yes, that is correct.

[Mugshot]

with the mod you suggested, there is a constant 1Meg resistance between the bias control and the point after the input cap, and lug 2 of the pot either moves closer to either points, am i right?

to bias trimmer <--------------[lug 1]
                                           >
                                           < [lug2]___________ to Q1 Gate
                                           >
                                           <
input ---||----------------------[lug 3]

Yes, that is correct.

haha, this will be finding its way into my EA trem build later tonight (im having unity gain issues, and while we're at it, http://www.diystompboxes.com/smfforum/index.php?topic=80479.0 thanks!)

props to you man! 

[cpm]

i think i once tried the mosfet version (rog) with no success...

anyway, there's not much need for higher gain than a unity buffer on the FET stage, since the following BJT stage does amplify by itself, since we are usually aiming at unity overall output, still needs some final attenuation to match input level. (or attenuate the input before the bjt)