Xotic EP-Booster

Greg · Post by **Greg** » 16 Nov 2009, 11:08

Here's the new Xotic EP-Booster.

"Inspired" by the EP Pre-amp.. but it turns out the circuit is quite different to the Pre-amp portion of the EP..
it doesn't use the same values or voltages.

.

Cute and compact little enclosure, but the build quality is pretty lousy IMO.

Why do they use the board mounted DC jacks with no relief when everyone knows how much trouble they can cause ?
Also, the only thing keeping the battery from the board tracks and DC jack is a cheapass piece of rubber and cloth tape... yuk.
The switch is from Run Run.
Transistors are sanded, but not very well.. one FET and one BJT.

Soundwise.. I swear this thing is clipping!
I'm going to get it on the scope and see when I get a chance, but it doesn't sound right to me. I haven't heard anyone else comment on this, but I could hear it as soon as I played it.. the higher the boost the more it clips, but I reckon I could hear it even at unity (to my ear anyway.. maybe the scope will prove me wrong).

Schematic is mostly done, but I'm finished for the day... I'll re-check it and post it tomorrow.

Enjoy

SPeter · Post by **SPeter** » 16 Nov 2009, 12:35

By itself it doesn't look so good, especially inside!
Thanks for the info!

himister · Post by **himister** » 16 Nov 2009, 13:10

Cute indeed.

Greg, would you be so kind to post couple more shots of pcb from top and bottom and other angles? I'd like to try to redraw this little fellow.
Cheers.

Greg · Post by **Greg** » 16 Nov 2009, 13:19

himister wrote:Cute indeed.
Greg, would you be so kind to post couple more shots of pcb from top and bottom and other angles? I'd like to try to redraw this little fellow.
Cheers.

I can post a bottom pic, but the work is already done.. I just want to check the schematic with a clear head and I'll post it tomorrow.

I really doubt you could do it from photos.. there are too many tracks under components and track switches from one side of the board to the other. I had to use the DMM quite a bit to follow where things went.
The layout is also very non intuitive.

himister · Post by **himister** » 16 Nov 2009, 13:23

Great. We'll wait for yours then.

'60Burst · Post by **'60Burst** » 16 Nov 2009, 21:18

What kind of jacks are those?

Greg · Post by **Greg** » 17 Nov 2009, 02:15

Schematic:

newly · Post by **newly** » 17 Nov 2009, 02:24

GREG thanks for the schematics.....but the 1n4148 at the power section....is it reversed?

bajaman · Post by **bajaman** » 17 Nov 2009, 02:57

Hi greg
something is definitely wrong with the schematic

for a start, the 4.7uf at the top is shown connected to ground at both ends, and the bias network for the emiter follower (buffer stage) is very weird

cheers
bajaman

Greg · Post by **Greg** » 17 Nov 2009, 03:59

Sorry guys.. and thanks for checking.
I rushed it a bit.. diode and LED cap now fixed.

Steve, I'll double check the bias network.

BTW - the cap on the LED cause it to flash like a camera flash for an instant and then settle down when switched.. on a dark stage at night it'd just about take your eyes away for a few seconds I think.
It's not on the board, but tacked on between LED and the pot.

Greg · Post by **Greg** » 17 Nov 2009, 04:45

I think the FET (Q1) is a 2N5457.

Greg · Post by **Greg** » 17 Nov 2009, 05:52

bajaman wrote:Hi greg
something is definitely wrong with the schematic
for a start, the 4.7uf at the top is shown connected to ground at both ends, and the bias network for the emiter follower (buffer stage) is very weird
cheers
bajaman

Steve

I missed a well hidden ground track.. well picked up.
Makes more sense now.. 2 x 10Ks form a voltage divider.. with 10uf power filter cap, and it changes effect of the 3300pf cap.
Schematic is updated.

Old Gregg · Post by **Old Gregg** » 17 Nov 2009, 05:58

I have a ClinchFX EP-Pre coming in the next week or so, when I get a chance I'll crack it and take pics to see
if Xotic really did do the almighty clone.

clinchfx · Post by **clinchfx** » 17 Nov 2009, 07:00

Old Gregg wrote:I have a ClinchFX EP-Pre coming in the next week or so, when I get a chance I'll crack it and take pics to see
if Xotic really did do the almighty clone.

You're welcome to open it up, but I build them well and they're not easy to dismantle.

They didn't do a clone. Here's the basic schematic of the EP-PRE

If you take a look at the original EP-3 schematic, serial numbers 9068-9450, you'll find that the EP-PRE matches it.
http://schematicheaven.com/effects/ep3_9068-9450.pdf

The EP-Booster has an output buffer, while neither the EP-3 nor the EP-PRE have an output buffer. The EP-Booster runs from 9V, while the EP-3 has a 20V power supply and the EP-PRE has a doubler supply that makes around 17.3V. About the only thing the EP-Booster has in common with the EP-3 (or the EP-PRE) is that the preamp is a common source JFET configuration. Component values and impedances are all very different.

My avatar is a shot of the EP-PRE PCB, complete with voltage doubler chip and capacitors. The electrolytics are all in the power supply, not in the signal path.

Peter.

Greg · Post by **Greg** » 17 Nov 2009, 23:56

clinchfx wrote:
Old Gregg wrote:I have a ClinchFX EP-Pre coming in the next week or so, when I get a chance I'll crack it and take pics to see
if Xotic really did do the almighty clone.
You're welcome to open it up, but I build them well and they're not easy to dismantle.

They didn't do a clone. Here's the basic schematic of the EP-PRE

Thanks for that Peter.. that's very cool of you, and makes it all a lot clearer.

For all the Drama on TGP.. it looks like these are quite different circuits.

'60Burst wrote:What kind of jacks are those?

The jacks are these: http://www.smallbearelec.com/Detail.bok?no=90

spaceace76 · Post by **spaceace76** » 18 Nov 2009, 07:32

decora wrote:i want the knob too...

i think it's a Davies 1510, which you can order from them in clear

http://www.daviesmolding.com/standard-p ... fault.html

their minimum order quantity is fairly low, 100 pieces, but unless you get a few more people in on it, or plan on using LOTS of clear knobs it's still sort of overkill.

that said if anyone's setting up a clear knob buy-in count me in

thanks for the schem peter! so they aren't identical, it seems like Xotic just saw your idea and ran (stumbled) with it.

Greg · Post by **Greg** » 18 Nov 2009, 08:25

Clear Knob discussion - Group Buy....
moved to new topic in Parts Sourcing.

RomanS · Post by **RomanS** » 26 Nov 2009, 11:29

Can somebody explain what the LED (on top of the circuit) is for? Thanks!

Greg · Post by **Greg** » 26 Nov 2009, 11:56

RomanS wrote:Can somebody explain what the LED (on top of the circuit) is for? Thanks!

It's the on/off indicator LED.

RomanS · Post by **RomanS** » 26 Nov 2009, 12:09

But there's no connection to the footswitch?
Sorry, I'm still a bit of a newbie, but I can't see how you'd switch the LED on/off with a common true-bypass/3PDT footswitch scheme?
Does the footwsitch simply switch off the power to the LED?

Xotic EP-Booster [traced]