Xotic EP Booster

Xotic EP Booster

Project description

The legendary echo machine EP-3 pre-amp as designed by Xotic. The EP Booster provides up to +20dB of boost with shimmering highs and lows. The DIP switches let you choose the boost frequencies, and EQ settings.

Verification status

I built it and it sounds awesome! It instantly replaced my LPB-1 as the Xotic has more presence and nice, singing notes with lots of sustain without sounding muddy, shrill or dark.


I've used this schematic found in a project page for the PCB version of the EP Booster.


The original EP preamp was designed to run on 18v DC. Using a higher voltage than 9v DC will provide a little more boost and some added clarity with less grain.

Just make sure C4 and C7 can handle the voltage with at least 25% over capacity!

Bill of materials

R1: 4.7K
R2: 8.2K
R3: 1M
R4: 33K
R5: 1M
R6: 1K
R7: 15K
R8: 10K
R9: 10K
R10: 1M
R11: 10K
R12: 47K
R13: 100R
R14: 10K Reverse log (C)
C1: 47nF
C9: 3.3nF
C2: 10μF
C3: 100μF
C4: 10μF
C5: 10μF
C7: 47μF
C8: 10μF
IC1: 2 pole DIP switch
D1: 1N4001
Q1: 2N5457
Q2: 2SC1815
4 jumper wires
12 trace cuts


Click here to see the bill-of-materials as a list or download it as a comma separated values file (.csv).


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Hi guys. I'm running mine @18volts now, better sound, more dynamics, less distortion. I love it. Try 18volts!

Help finding DIP switches

I've been trying to find the DIP switch on mouser but without luck.

I'd like to instead add two SPST switches so i can flip between them from the outside of the box.

Do I wire 1 switch on row 3 and 1 switch on row 4 so it connects over the trace cuts on column 9?



"Do I wire 1 switch on row 3 and 1 switch on row 4 so it connects over the trace cuts on column 9?"

That's the purpose of the switch: jumper the tracecuts.

I have the same question?

I have the same question? Does the switches connect line 3 to line 4 or do they connect the line back to itself?

Finished building this today.

Finished building this today. Sounds great. I'm thinking of building another replacing the dip switch with 2 case mounted switches.


It sounds very nice and the dip switches work too, I just leave them both on as default and I like that sound, no noise no hiss, just a beautiful tone....... Thank you very much for sharing this layout.


I replaced R2 with a 10K trimmer to fit the boost on my own taste... I like this pedal even more. Again thank you for this extremely good sounding layout.

Trannys not available

I have big troubles buying the required transistors for the layout.
Are there any suggestions about replacement parts, as the ones in the BOM are already discontinued.

Thanks in advance,


Found 'em, but new Problem

Ok, I found the needed components, and buit the booster today.

I chose to put all components on the non-copper-side, so I guess the layout is then just flipped ?

Anyway, I wired it according to this :

The problem I have now is, that when the FX is switched on, I just have static noise. Or - more specific - the 50Hz AC from the power line (EU here)..

Any ideas ??

H/L boost

I'm trying to trouble shoot mine. I have the boost working, I just can't seem to make the High/Low boost switches to make much of a difference. Just so I have a point of reference while debugging, which section of the circuit has to do with the high boost?

Did you check the

Did you check the schematic?

The switches are used to bypass either R7 (high) or C3 (low)...

I did see it. I just didn't

I did see it. I just didn't know which one was which. Thanks!


How many mA has as a limit?Is that depents also on the diode?


Fantastic tone!But I have scratches on the sound almost all the time and getting worst with second switch on. Please help!

No one??Pls! Is there a

No one??Pls!
Is there a possibility that the C9 and C1 be the problem? Because I put electrolytes of 50V so that I can use 18V DC.
Is it ok for the jumpers to touch the dipswitch?


Problem is not fixed finaly..After several minutes of playing I have scratches on the sound and volume drops..I assume this is because of a bad transistor or overheating. I 'm going to update if I find something

Fixed....first I put the

Fixed....first I put the jumpers, so the gun was probably not ready, that cause bad solder joints. I put fresh solder and sounds good.By the way I didnt have 10k pot and I try
47k works fine..

Electrolytes? They should be

Electrolytes? They should be non-polar MKT's or other film caps. MKT's can handle way more than 18v but that doesn't even matter because they are in the signal path.

What I mean is, that I used

What I mean is, that I used 50V electrolytic and I am asking if there is a possibility that this cause the small value MKTs to have problem.

Gain problem

I only get a few db of gain on this thing. Where might the problem lie?

No boost

I built this thing but I don't get a substantial boost out of it. The pot will turn up the volume a bit, but the overall volume (while pot is maxed) is less than unity. Where might the problem lie? I should note, I haven't hooked up the SPDT switches I'm using instead of a DIP. Although I gather that shouldn't affect the circuit not boosting the signal. Where might my problem lie?


Just to verify...the red boxes with dods means that you just open the circuit, but you don't place anything?

That's correct!

You have to cut the trace there. I always doublecheck if the cut is 100% using my multimeter.


The PDF for PCB version it's verified and ok ?

i have already make the veroboard verison but dosnt' work :'(

less boost

Hi, how can i reduce the volume boost to 0db

Replace R1 with 6K8

Replace R1 with 6K8

less boost

Thanks you for the tip, but this only reduce a little gain.
I want the boost pot to act as volume pot. or something like that, because when i hit the pedal it becomes to loud.
i already put a 100k out to act as a volume but its not the same, and i want to keep the 100R impedance at the end.


Hi there, I'm finding it difficult to get a 10k reverse log pot. Can it be a linear pot?

No problem, it will only

No problem, it will only alter the feel of the boost knob, not the function.

Thanks man!

Thanks man!

Problem with bass boost

The bass boost doesn't work for me.
I changed the caps C2, C3, changed the switch, changed Q1, it seems that nothing happens when I switch.
It's ok with the other switch on the 15K resistor.
Help me, please because it works perfect instead of that.

It's not really a big

It's not really a big difference but it should be noticeable, especially on higher boost settings (my experience)

Ok thanks for that - I have

Ok thanks for that - I have placed the input and output wires as far away as possible, replaced all with shielded cable, and rewired the footswitch as per your example. Still the squeel. Could it possibly be a problem on the board that I am not noticing?

I am just stumped for what is wrong

Thanks so much

Sorry, I can't troubleshoot

Sorry, I can't troubleshoot it here without exrta information like pictures and such ...

Please use the contact form to get personal help, or post a topic on http://www.diystompboxes.com/smfforum/ or http://www.freestompboxes.org/ for more help...

Thakns for this layout My

Thakns for this layout

My build works fine except there is this ear piercing high pitched squeel whether the effect is bypassed or on.

Tried to replace all wires with shield cable and use the inner part of the cable but still the squeel continues. Any ideas would be so appreciated


Try to place the in- and

Try to place the in- and outpus as far from each other as possible. And also ground the effect input whan in bypass: http://diy-layout.com/node/56


This thing sounds great :)



Hi, built the effect and it sounds great, but i've a question for you: How can i cut some bass coming out of it, in vintage and bright mode?? (in bass boost mode is unlogic cut bass because it was designed for it...) thx!!

You can try to reduce C8 to

You can try to reduce C8 to 220nF or even 100nF...

Where is the 12th trace cut?

In the board i see only 11 trace cuts... ?!?!?!?!


You mean the one beneath C8?

built this, great one


I've just finished building this. Works like a charm. The lower sw has only a very slight effect on the output signal however. Thanks for the layout and keep up with the good work on this site.


I really like this site and

I really like this site and plan on trying several builds....if I can get this one working, that is!

I tried to build the above vero layout (my first time using vero), but I'm not getting any signal once the effect is engaged. I do get a clean signal thru it when disengaged, so I believe I have the switch wired correctly. However, once engaged, the LED lights up but there is no sound. I checked the board closely to make sure there is no solder jumping over to the previous/next line. Also, instead of the internal dip switch, I used 2 SPDT switches off board.

Any ideas?

My apologies for the messy wiring, it was only supposed to be temporary until I got it working! Hopefully, these will help...

http://i414.photobucket.com/albums/pp22 ... 011420.jpg
http://i414.photobucket.com/albums/pp22 ... 011422.jpg
http://i414.photobucket.com/albums/pp22 ... 11422b.jpg
http://i414.photobucket.com/albums/pp22 ... 011423.jpg

Haha. never mind my last

Haha. never mind my last email... its late, I'm dumb. I got it working.

Thanks for another awesome layout!


Signal not passing through.

Hey Matt I'm experiencing the same problem you had. How did you manage to fix it?

Signal not passing through R4...?


Built the LPB-1 you have on here and love it. Thanks!

I put this on a strip board and it isn't working...

I trace the signal from Rail9-1 to Rail7-4 and for some reason, it isn't passing through to the rest of the circuit. I've swapped out 3 different 33k resistors, which all test at almost exactly 33k outside of the circuit... so I know the resistors aren't bad.

While I'm kinda new to this DIY thing, I follow directions VERY well and its a little disconcerting that this isn't working... maybe its mislabeled?

I tried a jumper instead of the resistor but it was oscillating, so I put a 1k in there and now signal passes through.

The problem I'm facing is that the pot/dips have no affect over the sound/volume/anything, so I'm at an impasse.

I've checked all the traces and cuts and they are all clean.

Voltages at Q1: G=3.72, S=2.99, D=3.0
Voltages at Q2: E=2.61, C=8.93, B=3.3 (when testing slowly drops to 3.03)

Hoping you can shed some light on the circuit or something that might be happening.


Are you sure you have all 12

Are you sure you have all 12 trace cuts?

You may use the contact form at http://diy-layout.com/contact for better help ;)

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