Xotic EP-Booster

g0d5_g1ft · Post by **g0d5_g1ft** » 07 Jan 2010, 14:54

riffstroker wrote:It has to be uF. I'm building this little Xotic thing next week when i got my electronic parts

Thanks, Im building this too, Im hoping to redo the layout to have it fit into a smaller enclosure, this ones board is a little too big.

g0d5_g1ft · Post by **g0d5_g1ft** » 14 Jan 2010, 08:02

built this last night, sounds nice with the bright boost...the bass boost i dont hear much of a difference.

as for the boost level, i had the knob turned all the way to the left, (boost 0) but I still get about double the volume of the guitar, what could I have done wrong? turned way up it gets a bit muddy, with tons of boost.

anyone else built this? or maybe suggest a better boost to build?

sinner · Post by **sinner** » 14 Jan 2010, 08:08

g0d5_g1ft wrote:Im hoping to redo the layout to have it fit into a smaller enclosure, this ones board is a little too big.

Have you managed to squeeze it?

Krinkle · Post by **Krinkle** » 14 Jan 2010, 18:57

Greg_G wrote:I ran it up on the scope, and as I thought it does clip with a decent signal going in.. I'll try to take some pics and post them.

At what signal level did it start to clip?

Greg · Post by **Greg** » 15 Jan 2010, 01:05

Krinkle wrote:
Greg_G wrote:I ran it up on the scope, and as I thought it does clip with a decent signal going in.. I'll try to take some pics and post them.
At what signal level did it start to clip?

I'll run it up again and double check.. and see if my camera will take good scope pics.

g0d5_g1ft · Post by **g0d5_g1ft** » 15 Jan 2010, 09:31

sinner wrote:
g0d5_g1ft wrote:Im hoping to redo the layout to have it fit into a smaller enclosure, this ones board is a little too big.
Have you managed to squeeze it?

it was a tight fit in a 1290NS enclosure, i had it going along the length of the case. too many wires going to switches and the pot, it didn't go in easily. I literally had to screw the enclosure shut. Good thing after I screwed it down nothing broke, and its still working...

@at my previous post
I take back the part where I said at zero boost (knob) the volume is almost double, its ok now I guess it was just because I just woke up when I tried it the last time...

anyone has a layout?

Krinkle · Post by **Krinkle** » 17 Jan 2010, 03:20

clinchfx wrote: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

I built this up on a breadboard, exactly as shown and it sounds excellent, but pretty noisy. I'm playing through a Strat with a Seymour Duncan 59 and a Metroamp 12000 series modified to Rockstah's cascade spec with a LarMar PPIMV. Adding this pedal to it really accentuates the VH vibe, convinces me that the Echoplex was one of the integral parts of his tone. I think this is an absolutely fantastic circuit.

I powered it with the 18volt rail of my DC Brick and used an MPF102 Jfet. Is that a noisy fet, is there a better one to use? I used metal film resistors and polyester caps except for a ceramic for the 220p. I keep hearing that the EP-Pre is not noisy. It'll probably be a while before I can get an EP-Pre, anybody have any good suggestions to make it quieter? There's a fair bit of boost from this circuit as drawn, does anybody know how Peter added the pot, turning it down a bit would probably help.

Krinkle · Post by **Krinkle** » 17 Jan 2010, 15:01

Took a closer look at the EP3 schematic and figured out how to add the volume pot. Hopefully turning it down helps with the noise. I don't care if I have to set it at unity and I don't get a signal boost at all, I just want the tone change I get with it. Very addictive.

soulsonic · Post by **soulsonic** » 17 Jan 2010, 18:42

2SK117 are excellent for low-noise audio circuits!

Krinkle · Post by **Krinkle** » 17 Jan 2010, 20:05

That's good to know, thanks. I don't have any of those at the moment, do you know if the BC245 is noisy?

I just rebuilt it with the output exactly as in the Echoplex schematic and I'm pretty much getting unity gain with the volume knob max'ed, which probably makes sense. I don't have a scope, I usually borrow the one from work or bring my stuff in to work.

I don't seem to be getting much noise with the changed output, but I realized that with the first build I had my power wire too close to my input and output jacks (had the breadboard laying on the floor with wires just laying there - pretty messy). I did like it with the extra output of the first build, though. I'll probably play it like this for a while and then decide exactly how I'm going to wire the output. This circuit does have some magic, for sure.

soulsonic · Post by **soulsonic** » 17 Jan 2010, 20:11

Breadboard always has a ton of noise. It's not a good judge of how noisy the final thing will be. Personally, my experience has been that MPF102 really aren't all that noisy, so perhaps it would be fine once it's all boxed up. If the hiss is really over the top, it might be an issue that the JFET got some damage from static. JFETs aren't nearly as sensitive as MOSFETs when it comes to ESD damage, but they can still get zapped sometimes, and one of the symptoms is a bunch of hiss.

Krinkle · Post by **Krinkle** » 17 Jan 2010, 20:53

Sounds right to me, thanks for the tips. I'm just going to play it for a while and see if I like it as is or if I need/want to play around with it some more. I think the noise was mostly the power wire touching the other wires. On my first try I didn't notice much hiss, so that might be a good sign. It sounds really good with my Strat with the SD 59 and and the Metroamp, you can easily hear how VH used it.

I have to try it with my other Strat and the clean channel on my CAA 3+ to see how it sounds. EJ has one of the best clean sounds I've ever heard and I've always thought that it was more than just a Strat into a Fender amp. I'm betting that there's a good chance that a little boost from this pedal with the slight frequency shift will color my tone the same way.

Old Gregg · Post by **Old Gregg** » 18 Jan 2010, 10:02

There's not much boost to be had in the EP-Pre, so it sounds as if you have it about right.

Krinkle · Post by **Krinkle** » 18 Jan 2010, 23:55

That's good to know. The only thing is that I seem to have just a little less than unity (to my ear, didn;t put it on a scope yet) with the volume pot maxxed out. I built it with the 220k to ground and 100k output resistor first and it had a bunch of boost and sounded killer, except for the noise. I may try that again seeing as how I'm pretty sure that the noise was the 18V wires touching the input or output jacks.

I have the parts for the EP-Booster and plan on building that up over the next few days, to compare.

Krinkle · Post by **Krinkle** » 22 Jan 2010, 01:46

Old Gregg wrote:There's not much boost to be had in the EP-Pre, so it sounds as if you have it about right.

I'm going to PM you with a question.

kdmay · Post by **kdmay** » 26 Jan 2010, 10:46

Krinkle wrote:
clinchfx wrote: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
I built this up on a breadboard, exactly as shown and it sounds excellent, but pretty noisy. I'm playing through a Strat with a Seymour Duncan 59 and a Metroamp 12000 series modified to Rockstah's cascade spec with a LarMar PPIMV. Adding this pedal to it really accentuates the VH vibe, convinces me that the Echoplex was one of the integral parts of his tone. I think this is an absolutely fantastic circuit.

I powered it with the 18volt rail of my DC Brick and used an MPF102 Jfet. Is that a noisy fet, is there a better one to use? I used metal film resistors and polyester caps except for a ceramic for the 220p. I keep hearing that the EP-Pre is not noisy. It'll probably be a while before I can get an EP-Pre, anybody have any good suggestions to make it quieter? There's a fair bit of boost from this circuit as drawn, does anybody know how Peter added the pot, turning it down a bit would probably help.

Would a J201 Jfet work ok for the EP-Pre? I have all the components lying around (by chance, just built a buffer) and thought I'd give it a go. Thinking of putting it at the end of my FX board to clean up the signal, sort of like a buffer but extra pixie dust....

kdmay · Post by **kdmay** » 26 Jan 2010, 11:50

kdmay wrote:
Would a J201 Jfet work ok for the EP-Pre? I have all the components lying around (by chance, just built a buffer) and thought I'd give it a go. Thinking of putting it at the end of my FX board to clean up the signal, sort of like a buffer but extra pixie dust....

Also, one question as I'm new to translating schematics to strip board layouts. Where the base of Q1 is connected to ground via R3, am I correct in assuming that C3 is connected in parallel? If so, do I just also connect it to ground. In simple terms, signal hits C3 first which is connected to ground, then it hits R3 next which is also connected to ground?

Apologies if this is a little crude, I'm still learning!

Krinkle · Post by **Krinkle** » 27 Jan 2010, 15:22

It hits R3 and C3 at the same time. R3 and C3 both connect to Q1 on one end and ground on the other. Even though you may use a wire, consider anything that touches the bottom of Q1 and the tops of R3 and C3 the same "node" as they are the same point electrically.

Greg · Post by **Greg** » 05 Feb 2010, 06:09

Greg_G wrote:
Krinkle wrote:
Greg_G wrote:I ran it up on the scope, and as I thought it does clip with a decent signal going in.. I'll try to take some pics and post them.
At what signal level did it start to clip?
I'll run it up again and double check.. and see if my camera will take good scope pics.

As promised.. 'scope pics of the Xotic EP Booster.
It clips from moderately to quite heavily on the lower frequencies.
I could hear this when I first tried it and can't understand why I haven't seen anyone else comment.. maybe they vary ?
Meaurements are at Full Vol, clipping is reduced at lower settings but still very noticeable esp. from about 11.00 o'clock up.

600mV p-p - 80Hz - Full Vol

600mV p-p - 1KHz - Full Vol

1V p-p - 80Hz - Full Vol

1V p-p - 1KHz - Full Vol

brightboy · Post by **brightboy** » 05 Feb 2010, 21:40

Did you properly compensate your scope probes before taking those pictures?

Jeff

Xotic EP-Booster [traced]