Xotic EP-Booster  [traced]

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Re: Xotic EP-Booster

Postby alexradium » 09 Jun 2012, 09:49

transistor could be anything,its a buffer,all the gain comes from the first jfet.
as long as its good working,electrolytic cap can be anything over 10V.
what is your layout?
post a pic
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Re: Xotic EP-Booster

Postby jimosity » 10 Jul 2012, 13:59

While reading thru this one, I kept seeing guys asking about how to wire it up with a switch and such.
Since schematics don't normally show the switching, I figured I'd do a quick pic to show how a schematic and switch wiring work together.

Use this wrapper from the awesome Beavis Audio site; I use this for almost all of my stuff.
http://www.beavisaudio.com/techpages/StompboxWiring/

But to crudely show how a schematic works with offboard wiring; here's how it translates.
(excuse my less than 2 minutes of photoshopping mess)

Image

Actually, this is probably slightly off because they show the LED in the schematic - which most usually don't (at the top, near the 4.7uF cap) - so the LED shown by the footswitch isn't necessary. (Just assume for this particular schematic that the switch is only using the two right columns; the left column is only for the LED anyways). That being said, it looks like you could get by with a DPDT instead of a 3PDT based on this schematic.
Most schematics don't have the LED shown; so in general, my pic there makes sense..

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Re: Xotic EP-Booster

Postby Fermusicman » 23 Mar 2013, 00:14

Hello everybody, recently I bought one, when compared with my prototype, the original has 6 dB more gain and transistor voltages do not match.
Anyone know what transistor has the same pinout and can give more gain? :hmmm:
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Re: Xotic EP-Booster

Postby alexradium » 23 Mar 2013, 10:40

Fermusicman wrote:Hello everybody, recently I bought one, when compared with my prototype, the original has 6 dB more gain and transistor voltages do not match.
Anyone know what transistor has the same pinout and can give more gain? :hmmm:
i use 2N5457,i can get 20 dB out of it,the J201 is not so gainy with the stock polarization.
can you tell me the drain voltage on the original?
is it the last version with the 0dB switch?

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Re: Xotic EP-Booster

Postby Fermusicman » 23 Mar 2013, 20:36

Well, thanks for the tip, I will try the 2N5457. The supply voltage before the diode is 9.8V, after the diode is 9.6V, and the drain is 7.45v.
This one is version 3, and brings the switch to 0 db. By the way the diode is 1N5819.

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Re: Xotic EP-Booster

Postby alexradium » 23 Mar 2013, 20:52

Fermusicman wrote:Well, thanks for the tip, I will try the 2N5457. The supply voltage before the diode is 9.8V, after the diode is 9.6V, and the drain is 7.45v.
This one is version 3, and brings the switch to 0 db. By the way the diode is 1N5819.
how is the 0dB feature done?
i tried that raising the source value to 10k,not sure if thats the best way...
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Re: Xotic EP-Booster

Postby Fermusicman » 23 Mar 2013, 21:46

I thought the same thing but they do not do that, is a switchable resistor at the output of C1815. I will review and give you the details.
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Re: Xotic EP-Booster

Postby alexradium » 23 Mar 2013, 23:10

Fermusicman wrote:I thought the same thing but they do not do that, is a switchable resistor at the output of C1815. I will review and give you the details.
then i guess its a 18/22k in series to form a voltage divider...
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Re: Xotic EP-Booster

Postby Fermusicman » 24 Mar 2013, 21:24

:secret: You're right, it's a 18k resistor, so it´s; emitter C1815, 10uF cap, 100 ohm resistor, 18k resistor in series, 47k resistor to ground.
The 18k resistor at each end has a pin of dip switch.

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Re: Xotic EP-Booster

Postby Fermusicman » 28 Mar 2013, 00:54

Two things more; the diode is type Schottky, I think, and I try the 2N5458 with good results, the gain is nearly 20 dB, plus pinout is DSG, like the original.
Now when I compare them, original and my prototype side by side are very, very similar.
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Re: Xotic EP-Booster

Postby jmwreck » 11 Jul 2013, 15:30

bigorangefan79 wrote:
miamimart wrote:Has anybody traced the EP Booster version 2....the one with the unity gain feature? Thinking about doing a build, but wouldn't mind that feature. Thanks.


Just put a trim pot between the grounded lug of the volume pot and ground.


It's acts as a volume, right?
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Re: Xotic EP-Booster

Postby guitardanhx » 31 Jul 2013, 10:57

Just to chime in guys - I just built this pedal and was also finding it far too loud on minimum gain settings. Simple solution - replaced the 100r resisitor with an 18k. Seems to work like a charm now, unity gain at minimum and still a nice amount of gain at full boost.

D
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Re: Xotic EP-Booster

Postby alexradium » 31 Jul 2013, 12:03

guitardanhx wrote:Just to chime in guys - I just built this pedal and was also finding it far too loud on minimum gain settings. Simple solution - replaced the 100r resisitor with an 18k. Seems to work like a charm now, unity gain at minimum and still a nice amount of gain at full boost.

D
it was described 5 posts earlier,in detail....sight problems anyone?
just kidding,lol,take it easy
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Re: Xotic EP-Booster

Postby guitardanhx » 31 Jul 2013, 12:10

Haha yeah I know - I think the point I was trying to make is that there's no need to add the 18k in series with the 100r, unless you're making it switchable. Simply removing the 100r and replacing it with a 18k is a much easier solution if you've already built the board. :D
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Re: Xotic EP-Booster

Postby premiumplus » 31 Aug 2013, 16:12

I put one together last week from the verified vero layout, and it sounds great. Really, really good! I can't turn it off...one thing though, and I've retraced my vero several times, and tried different j-fets, etc...
The switch that bypasses the 15k ohm resistor doesn't really have an audible effect. On my scope, with a sine wave input from my generator, it makes the waveform jump when I engage it, but it doesn't cut or boost at any frequency. On the other hand, the switch that engages the 100uF cap significantly boosts all frequencies except the high freqs. (By memory, I think the cutoff is around 1800 to 2kHz).
Not having ever heard a production EP Booster, I don't have anything to compare to, so I don't know how effective the treble boost switch is. And even though it doesn't show much effect if any, on the scope, it does seem to clarify the highs a bit. But that could be a psycho-acoustic effect too. Like I said, it sounds just stellar, but I'm puzzled by the lack of effectiveness of the treble boost switch.
Any ideas? :scratch:
Vinyl rules.
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Re: Xotic EP-Booster

Postby Beedoola » 31 Aug 2013, 17:09

I also built one using Ivlark's layout on his blog. It sounds awesome! I agree about the treble switch. I do hear a difference, though subtle. It was more noticeable when using it with the gain channel on my amp; boosting the preamps.
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Re: Xotic EP-Booster

Postby gambit07 » 19 Nov 2013, 09:28

Theo wrote:Hi, I've built this booster and changed the layout so dipswitches could be used , dimensions of the print are 45x25mm
I like the sound , there's not much volume boost but it works well with my guitar and amp , slightly fattening the sound .

[ Image ]
[ Image ]



hi, i built this one using your layout.. It's not working.. There's a big volume drop, and I can't help but notice, the switching of that 100uF cap to Q1.. i think it's the other way around.. i don't know.. it doesn't seem to coincide with the schematic.. and judging from your tiny picture here.. you also switched it.. (the stripe of the 100uf cap is on the square pad of the pcb)

im not getting any boost, as a matter of fact, it drops my volume big time.

what could be wrong with this? and what lug on the gain pot should "gain" be connected with.. is it 3?
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Re: Xotic EP-Booster

Postby zedsnotdead » 25 Feb 2014, 12:10

Hello,

I am wiring and soldering components using moska's layout (http://www.freestompboxes.org/viewtopic ... =60#p93713).
He uses Q1=J201 and Q2= 2N5088, but Greg's schematic uses Q1=2N5457, Q2= 2SC1815.
So is it ok to use both references?

Also, i dont know if someone noticed this, but if you use moska's layout, be aware that Q2 is not reflecting the correct pinout of the schematic.
2N5088 = EBC (moska's)
2SC1815= BCE (greg's)
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Re: Xotic EP-Booster

Postby alexradium » 25 Feb 2014, 12:42

zedsnotdead wrote:Hello,

Also, i dont know if someone noticed this, but if you use moska's layout, be aware that Q2 is not reflecting the correct pinout of the schematic.
2N5088 = EBC (moska's)
2SC1815= BCE (greg's)
Its in the previous page!
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Re: Xotic EP-Booster

Postby zedsnotdead » 25 Feb 2014, 13:14

Its in the previous page!


*MEGA facepalm*

You are right! How did I miss that!?

Thank you alex!
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