EA Tremolo - Depth

[mydementia]

I just perf-boarded up an EA Trem (from the GGG layout w/the ROG 'pulsing' LED mod - very cool).  The effect is awesome - but the depth knob doesn't seem go deep enough.  On my Vox Tonelab, the trem depth goes from 'pretty' to heavily pulsating.  Is there a mod to have a heavier trem effect?

I built per the GGG layout/part list but subbed a 2N3904 for Q3 and used J201 JFETs.

Thanks for looking.
Mike

[SISKO]

hi, well the EA its not recognise by it deep sound, but for it smooth effect.
there are som mods. but i basicaly persuade you to build the tremulus lune. in www.pisotones.com you have a lite version if you are interested.
it just the best tremolo that i`have ever heard..
well my 2 cents
bye

[mydementia]

Thanks for the recommendation SISKO - but I've already built the EA Trem and would like to get it sounding as good as the demos on the ROG site.  Since I used the GGG part list/layout (for the most part), I didn't use the MOSFET input stage...I assume this won't matter much since the trem effect is happening further down the line...
All my JFET/Tranny voltages look good (per the GGG references), so I assume it's working just fine - just not as deep as I'd hoped.  What difference does my subbing in a 2N3904 for Q3 make?  (I saw that Paul Marossy used one instead of the 2N5088 - he's been at this a lot longer than me so I figure it can't be too wrong!)  If it's major, maybe I'll try to find one at my local elec store today...

Does anyone have a working link to the '1968' article?  When looking through this forum, I see a lot of references to increasing depth per the original article but can't find it...

Thanks for looking.
Mike

[SISKO]

here we go..
1st... definitely  Q3 to a 5088/9 you´ll have a deeper oscillation since it has a way more gain..
anyway you can modify the circuit... here we are..
you can lower R7, in this way we are adding more voltage to the jfet.
i recomens you to start with 100K and lower if necessary.. but be care ful with pops.
in www.pisotones.com you have some mods to eliminate the pops check it out.
well it almost a MUST to change this resistor.. or make it a pot .. like a fine tunning
well post the results... I'm gonna made this mods.. and it change in a good way

bye
pd1:i couldn't´t have the deepest tremolo that i need ,so i build the tremuluslune

pd2: you can always replace the oscillator .but the EA it knows by it´s grate smoot tremolo

[SISKO]

Depth and Speed controls have been adjusted to my preferences. The first 25% of the original 1M Depth pot rotation resulted in no audible tremolo effect to allow use as a pre-amp. The Depth pot has been decreased in value with carefully chosen resistor values added before and after. The Rate pot value has been increased and a reverse-log taper offers a better feel. However, a linear or audio taper pot can be used for the Rate control with no ill effects. The 2k2 resistor which precedes the Speed control has been reduced for a faster maximum oscillation rate.
R7 120k
depht pot 250k

2cents

bye!!!

[Ge_Whiz]

The critical component in the modulation process is the JFET. These are notorious for wide specifications. I have no depth problems on my EA trem - I used a 2N5457 - and my first guess is that you might have to socket the JFET and try a few to optimise the depth.

[Processaurus]

I haven't tried this on my EA, but a knowledgable forumite posted a way to get WAY more depth and also more headroom on the EA by adding a constant current source to the drain of the MOSFET (if you're doing the ROG design), or emitter (if you're using the Geofex/GGG schematic).  It looks like it should solve the problems people have with that design, but I guess it kind of slipped under the radar. 

http://www.elixant.com/~stompbox/smfforum/index.php?topic=35217.0

Scroll down and read Transmogrifox's 1st post about for his schematic & notes.

[nofretsplz]

I don't remember if my EA Trem has any mods (I built it a couple of years ago), but it can fully oscillate the volume on/off...but it still sounds incredibly close to the stock trem on my Fender Deluxe Reissue. Don't give up on it!!!

One fun trick I found is to place it in line with a Great Cheddar (or other distortion/fuzz), crank up the oscillation and time your notes so that the picking is hidden...instant synth.

[George Giblet]

It's possible subbing Q3 with a 2n3904 has reduced the output of the oscillator, that will reduce the depth.

The easy thing to do is use a high gain transistor a see if that does anything - if not move onto other mods.

[mydementia]

I finally got my 2N5088's in the mail today - success!  Amazing how the parts on the BOM work best...
This trem is awesome - highly recommended build!