Saturday, 4 February 2012

EA Tremolo - Modified ROG

Here is an adaptation of the EA tremolo with the schematic done by runoffgroove.

Their notes on it:

Modifications to JD Sleep's version are:

    * Input buffer and main gain stage have been combined into a single MOSFET stage designed by Gez Paton.
    * The "pulsing LED" by Darren Inwood and Rob Strand.
    * 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.

"marrstians" reports that the pulsing LED can also serve as a status indicator when using a 3PDT bypass switch. Simply use the third pole of the switch to break the connection between the LED and the collector of Q3 when bypassed.

Modification for LED status indication:


  1. this thing works great. LED mod too.


  2. Hi! First i would like thank for the layouts, these are awesome. I'm a new DIYer and was wondering if someone can help me out with this: BYOC tremolo kit is also based on EA Tremolo, but it's a bit different. Can someone give me some insight on that? Mainly why byoc has 4 transistors?

    1. I guess it's the first modification part where it states "combined to single mosfet..."? No need to answer if im right, over and out :)

    2. Have you got a link to the BYOC Tremolo? It's labelled modified in this layout because that's how it's described on the ROG schematic.

    3. Seems you got it :)

      Welcome anyway!

  3. Has anyone experienced distortion with this, and has anyone used 2SK170 on Q2?

    1. Yes I have, you have to cross the top 2 legs though. Oh and it does not sounds as vintage and warm IMO but they will work

  4. hi friends,

    in my EA, the range of the depth pot and the rate is very short...

    in particular, the rate pot starts changing the speed at half or more...

    how can I resolve these problems? thanks so much! :)

    1. please, anyone can help me?

    2. What you describe is not how it normally functions, you have messed up somewhere, are you sure you have the right value pots?

  5. :O
    yes...I'm sure!

    I'll check again and again..

  6. Hi there. Thank you so much for all these layouts and sharing them with us. They must take alot of your time and I really appreciate it.

    Do you do requests? I once built a BYOC tremolo and it sounded awesome. I know it's an EA tremolo so I built this one and it's not quite the same. (different value pots, a transistor missing etc.)

    I'd so appreciate it if you could do a layout for the BYOC tremolo. The schematic for it is on the build doc on their website.

    :-) please please please!!!!

    1. The BYOC is a modified Dyna Comp. So you've got the Dyna Comp layout here, Ross Compressor, Keeley Compressor or Emma TransMORGrifier which are all variations on the same circuit and will be similar.

  7. You have any thoughts on how to do the dual depth mod for this?

  8. Third time is the charm!
    I built this with a Torchy and a Dragonfly layout unsuccessfully. This one fired up right away.
    The tapers are great, and it is pretty much as Fendery as I wanted it to be.

    Thanks guys!

  9. What would be the way to build this withou the pulsating led? I have put a trimmer at about 67k ohm in its place, based on experimentation, but I don't know which is the right way to revert the led mod


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  12. I've built this one up over the last few nights. Tonight was the big turn on :) Not a complete failure (yet!!). I'm getting a lovely clean signal through but no tremolo (the depth and rate pots are having no impact at all to the signal. Also, the LED mod, which should pulse with the rate time is just constantly lit.
    This is only the second pedal I've made, so I could have made a schoolboy error somewhere but I've checked over things a few times and can't yet figure this one out. Any help would be appreciated, I'm sure I'm not far away on this one!


  13. It works!! I have tremolo!! I used a couple of equivalent transistors ( I used a 2n7000 and a BC550 in place of the BS170 and 2N5088) in this build purely because of availability. This is what caught me out. The pins were reversed so I had 2 0f the 3 transistors soldered in the wrong way around!!! No wonder it didn't work. Now I've got tremolo and a decent level/volume. Really satisfied that I've built this and its working but I am disappointed with the lack of tremolo depth. I've used a 250k lin pot for the depth, I don't know what impact that has on effect depth but its not currently getting deep enough. Its currently (with the depth pot at 10 (100% on)) very mellow, barely cutting in to the dry signal, basically its max depth setting is what I would use as a subtle tremolo. What can I change or what do I need to review to get the depth control working properly?



  14. Sorted all working properly. Switched out the third cap for a 2n5088 and it worked straight away. `really chuffed with it :)

  15. Built this tonight and I've got the pulsing light and a great boost, but signal is passing through as tremolo. I've used 2N7000, MPF102 and a BC550.
    I did bend the legs of the MPF to fit the pinout...

    This is driving me crazy. :/

    1. Measure all the transistor pin voltages and post them here to see if it gives us a clue

    2. So
      Q1 gets: D:4.76, S:1.74, G:1.26
      Q2 gets nothing... so I'm guessing there's a fault where it's not getting power. :/
      I'm wondering why the hell...
      Q3 gets: C:4.61 (fluctuating), B: 0.59, E: 0

      Hmmm... :/

    3. So from the the link that goes between Q2 and the trimpot there is no voltage whatsoever. o.O

    4. Off the 22uf electro I'm getting .98v going in but nothing coming out...

  16. Hey there,

    I too need some help with this.

    This is the first board i've put together from this site - firstly i'd like to say what a wonderful place this is!! thank you so much for all your amazing work!

    So, my build's gone pretty well considering I'm a maximum noob.
    The vero board layout was so easy to follow - all instructions clear - great!
    The board powers up, LED lights up - great!
    Sound comes through and the boost works fine - great!
    ...but the Trem's not working as of yet, and the LED is on solidly (no oscillation) :(

    The interesting thing is it does work, but only for a second if I disconnect, then reconnect the LED - the light dims and fades back in, and the volume swells. But this effect is only momentary, as though a capacitor is charging to capacitance, and when fully charged - 'no more trem for you'.

    I've double checked everything I can think of:
    - Components places, values.
    - Electrolytic cap polarity.
    - Remade all connections (encase of cold solder joint).
    - Searched the board several times to look for shorts, and run a scalpel between the tracks on the vero.
    - Pulled up all the data sheets for the transistors and quadruple checked the polarities (Q1-BS170, Q2-2N3819, Q3-2N5088)

    I know I'm close to having it working.
    Any help would be great!!



  17. Update.

    Just as 'myfriendtom' posted in June, I have no voltage the other side of that 22uF Electrolytic cap, and nothing on any of the pins of Q2.

    Any help would be top :)


  18. Sorted!

    Decided to go through every earthed component, testing that they were making a good connection to ground with my multimeter. Sure enough the 15k resistor that grounds those 1uF caps by Q3 wasn't making good contact - blobbed some more solder on, and everything works perfectly!!

    Super chuffed! Stoked in fact.

    Guitar tech for a tour this week, but when I'm back going to house this little puppy.
    Will post photos and maybe a video when it's looking nice :)

    This site rocks!!!!

    Blues Driver 2 next...


  19. Hello,

    Anyone could tell me what is the difference between the SPEED and RATE for the Tremolo Effect?

    Thank you

  20. I just built this pedal using the 2N7000 for Q2. It worked with Q2 in both orientations, however the tremolo is very choppy and almost square wave sounding. I swapped Q2 for a 2SK30 and it's perfect now!! If you cant find the recommended part for Q2, use the 2sk30. The round side of this the 2sk30 as Q2 should be facing the left of the board.

    1. Also, the 2N7000 caused the knobs to function strangely. The trem would suddenly cut out when I turned the rate up, or down, and it was annoying. The new q2 fixed that up.

  21. You should really incorporate RC filter for 9V supply. It's super easy to add! Cut at fourth hole, first row. Add 100R resistor across the cut and add a 100 uF cap across first and third row. Solved all my noise problems.

    I also replaced 180R resistor by a 1K Lin pot. It allows me to control the amount of distortion from the MOSFET, all the way from very clean to nice vintage overdrive. Very very nice tremolo this is!

    -Harri M

  22. I really struggled with this one today. Built it and it worked perfectly. Boxed it up and that worked fine, too. Until I plugged in the guitar and the pulsing indicator stopped pulsing. I made a sloppy soldery mess trying to reconfigure it a million times, but in the end had to settle with the 'indicator always on' option (pre-'modified' version) The thing that's killing me is that I really think I've gotten this working in the past! Gaaa! Anyone had this problem and solved it?

  23. Hello friends.
    I just built one of these and it works fine. I do not have much knowledge of electronics, so I have a little doubt: removing the volume pot (100K Log) where / how would my output be? Would I simply use the point indicated with "Volume 3" for this? Would I have to add some more resistor / cap in the layout?
    What I intend is to use only the guitar voluma pot.
    Any help would be welcome !!!!!!

    1. colocando o cabo do volume 3 para o Output direto você terá o máximo volume do circuito o tempo todo. Você não tem que adicionar nenhum cap ou resistor.

  24. Excuse me, but my English is not very good because I'm from Brazil.

  25. I might be nuts, but is the graphic representation of Q2 backwards given the pinout of the 2SK117?

  26. Hello everybody. And thanks for answering me Iago; I'm controlling the volume on the guitar itself.
    But what brings me back is this: I built another EA Tremolo as you can see in "" with the following connection mode "https : // file = xnex3m3nm94z7hkrdpb.jpg ", and a very loud plop occurs when you turn the pedal on or off. The noise is very strong indeed. The only thing I tried to do was increase the value of the R1 resistor to 2M which resulted in nothing.
    Does anyone have any ideas how to solve this?

    1. I think it's possible that the removal of the volume potentiometer is causing this. Leave R1 as 1M or 2M, won't make a difference. Try this: add a resistor to the volume 3 spot on the board, or to the end of your "volume wire", the other leg of this same resistor goes to ground. Use values starting from 22K.

  27. Hi Iago
    Thanks again for replying. Let's see if I understand (my knowledge of electronics is not very good). I modified the board layout a little bit and it looked like this: "". What do you propose is the addition of a resistor to the board output according to this same layout? I look forward to it, Egon.

  28. Hello everyone.
    I have a problem that as much as I read some articles out there on the internet and some tips received, I still can not solve. I don't know much about electronics, but some things are not that difficult, which is why I take a little risk in this area.
    Well, here's my problem:
    In the first photo you can see a “thing” that I built and I venture to call it a pedalboard and this one is composed of a Tremolo, a Fuzz and a Wah Wah.
    Tremolo is an EA – Tremolo that you can see at on page 2 more exactly.
    Fuzz is X Fuzz by Deadastronaut and it's in
    And the Wah Wah in
    The effects work well, but my problem is the PLOP noise when I turn the tremolo on / off. Only the tremolo. It's a very loud crack, sounding like a gunshot (if the amplifier is at full volume, of course).
    I have tried some things such as:
    1 - place resistors of varying values ​​in the input and / or output of the board up to random use from 22K up to 3.3M (individual) and up to 5.5M (parallel);
    2 - put a 50K trimmer on the output, because I removed the volume pot (to gain space and aesthetics, placing a 1M resistor on the output to eliminate noise that appeared;
    3 - Use another 3PDT switch (fuzz more accurately and that does not do such a PLOP, because I thought it could be a mechanical problem in activating the tremolo switch 3PDT;
    In the 2nd photo I show the differences between the original Tremolo and my project plus some of the above mentioned attempts and the 3PDT key connection I use.
    Well that said, I appreciate any help and especially the interest of anyone who can give this help,

    Photo 1:
    Photo 2:
    PS .: Special thanks to Iago who has already tried to help me and I hope it stays that way.

  29. Hello again.
    I still didn't solve my problem. On the other hand I would very much appreciate if anyone could tell me, please in a very simple language, what exactly is the function of the Trimmer 100K in the above layout. Actually what would happen if it were removed, as I would like to try this layout by removing the volume pot and this trimmer, something similar to what I did and already mentioned here in this forum. Thank you.