EP-PRE revisited

[Good Guest]

So if I understand correctly, you could run a splitter cable into two ep-3's and run these two in parallel? What would that bring as far as sound goes? There was talk that Eddie possibly ran the two ep-3's in parallel, right?

Once you run them in paralell your signal will degrade from loading right of the bat....see impedance does matter, hence the purpose of a buffer. Another fact is when an ep3 is in bypass it's just the echo that is, not the preamp ..the preamp is always on, with all it's slight phase shift , inversion, and tone coloring affecting the guitar signal. That's not to say it can't be bypassed another way like with an a/b box. Like everything else related to Ed's tone ..it's all just speculation till concrete evidence states otherwise.

[Coot Boy]

I had a chance to crank the Tillman FET caper through an amp and I must say, I love this little thing. I only played an SSS strat but man this is a great circuit, you could call it a clean boost if you like but to my ears it adds just a little "something" Maybe this is what everyone is talking about? I almost bought a Clinche EP Pre but ended up not getting one so I can't say how this compares but it cost nothing to make and I like it better than my current clean? boost pedals, it makes me think I should probably ditch some if not all of them, none of them are as good as this. There is a little top end oscilation when you dime the guitar and take your hands off the guitar, I'm hoping this will be fixed when I put it in a metal box but if not, no biggy. I wouldn't want to add any extra gain either or any more top end. If there are guys out there thinking of buying a FET preamp, I would highly recommend slapping a Tillman together first, you might just stop there as I have.
Thanks to Leadguy for posting the link to the Tillman and to Spaceace76 for alerting me to the pinout debacle.

[spaceace76]

the noise should go away once it's boxed up. you were using a single coil so that could be affecting noise as well. glad you got everything sorted out!

[Doug H]

cxool, thanks for that link, I'm going to build one of those tillmans into the front end of my byoc 10 band as sort of a "Van Halen-izer".

Great thread, the mystery continues to unravel.

[Coot Boy]

Here's a couple of pics of my bodgy Tillman FET pre, the purple led looks great, not so good in the pic, I find myself not wanting to turn this thing off, when I did, I put it straight back on again. Anyway, just wanted to show that anyone can botch one of these up, it doesn't have to be pretty. I had to double up on some resistors as I didn't have the correct values in stock. The input Jack plug goes into the left socket, I'm a lefty.

[leadguy]

Great work.

The real Echoplex EP3 FET preamp has a high frequency cutoff filter to stop it picking up radio stations and other things which is the 100k resistor and the 220p cap in the input of the real Echoplex schematic on page 1 of this thread and then it goes to a .022uf coupling cap and a 1M resistor which sets the input impedance. The Tillman just has a 3M resistor setting the input impedance so the Tillman can be modded with the Echoplex EP3 front end resistors and caps to help prevent high frequency interference.
The Tillman gain can also be increased by using varying caps across the 2.2k source resistor like the Echoplex EP3's .022uf up to 10 uf or whatever.

According to Ed, Rudy and Dave, the Echoplex(es) and therefore the Echoplex(es) FET pre was/were the last in the chain before the amp on VH1 except when Ed was using the Univox which was left out of the chain for most songs except Eruption and for live venues the Univox was hooked up to a different set of amps for the YRGM/Eruption changeover and for most live songs the Echoplex(es) was/were the last in the chain before the amps.

In the Japan photos Ed has sometimes got each Echoplex with a EQ in front of it and that would point to the Echoplexes being in parallel because 2 Echoplexes and EQs being in series might be a bit too much but that's for live venues and in the studio he might just have had 2 Echoplexes in series or in parallel depending on how he hooked them up to the amps channels.

[Coot Boy]

the Tillman can be modded with the Echoplex EP3 front end resistors and caps to help prevent high frequency interference.

I think this might be a good idea as the one I just made does indeed have some high frequency issues when you aren't touching the guitar. Cheers.

[leadguy]

A couple of Volume pot ideas

http://www.albertkreuzer.com/pics/el/pr ... ot_sch.gif" onclick="window.open(this.href);return false;

The Tillman FET 51k output resistor gets replaced with a 50k pot.


http://www.blueguitar.org/new/schem/_gt ... laster.jpg" onclick="window.open(this.href);return false;

http://www.freeinfosociety.com/electron ... laster.gif" onclick="window.open(this.href);return false;

The 50k pot and 10uF cap on the source resistor will act as a filter and alter the gain and tone of the preamp, similar to the Exotic EP.
The 10uF cap is large enough as to not get a treble boost happening, it seems to boost a wide range.

[jape88]

FYI Peter will be back at production of the EP Pre next week, so He's sifting through the back log... then production should start.

[Coot Boy]

A couple of Volume pot ideas

http://www.albertkreuzer.com/pics/el/pr ... ot_sch.gif" onclick="window.open(this.href);return false;

The Tillman FET 51k output resistor gets replaced with a 50k pot.

http://www.freeinfosociety.com/electron ... laster.gif" onclick="window.open(this.href);return false;

The 50k pot and 10uF cap on the source resistor will act as a filter and alter the gain and tone of the preamp, similar to the Exotic EP.
The 10uF cap is large enough as to not get a treble boost happening, it seems to boost a wide range.

Thanks mate, interesting stuff, well worth doing more experimentation with this thing.

[flieger67]

FYI Peter will be back at production of the EP Pre next week, so He's sifting through the back log... then production should start.

That's great news! I was getting worried for a while: I know that he's had some health issues.

[plexified]

Yeah , I' on board too , I tried a Bi ~ Fet pre amp for acoustic guitar only , just a boost and small para eq and viola . what a beast . Thanks GoodGuest , I'm gonna try to build some stuff too .

[Krinkle]

the noise should go away once it's boxed up. you were using a single coil so that could be affecting noise as well. glad you got everything sorted out!

Pm'ed you

[leadguy]

The Echoplex EP3 doesn't have a output buffer which is no big deal if it's output is being fed into a high impedance input like a Marshall amp.
The Echoplex EP3's unbuffered output would only be loaded down by it's output going into a medium/low impedance.

The Echoplex EP4 (which I've just got) has a similar FET preamp to the Echoplex EP3 with some minor differences and the EP4 also has an output buffer (A FET and a unity gain transistor Emitter follower buffer with a low output impedance) so the output of the EP4 won't be loaded down by it's output going to a medium/low impedance.

Basically that's why an output buffer was added to the Echoplex EP4 because the Echoplex EP3 output can be loaded down if it goes to a medium/low impedance.

Whether the Echoplex EP3 or EP4 has an output buffer doesn't really matter if they are going into high impedances but the EP4 can go into medium/low impedances as well and the output buffer would not colour the FET preamp much at all and the transistor output buffer would really not be noticeable in the actual tone much, if at all.

So the Echoplex EP4's output is a bit similar to the Xotic EP which also has a FET preamp and a transistor output Emitter follower buffer with a low impedance output.

The Boss MT-2 in bypass has a FET buffer input and a transistor output Emitter follower buffer with a low impedance output.

I've tried the Echoplex EP4 and the Boss MT-2 in bypass and both have similar characteristics due to the input FET preamp/buffer.

The output transistor Emitter follower buffer with a low impedance output won't affect the sound of the FET preamp much at all.

Like the Echoplex EP3 FET preamp, the basic Tillman FET preamp doesn't have an output buffer either although there are Tillman FET preamp output buffer addons.

If the FET preamp is always going to go into a high impedance then an output buffer is not really necessary.

[Doug H]

Here's my byoc 10 band with a tillman inspired FET stage at the end. I sacrificed the battery space to wire up the circuit. I must say it sounds pretty cool.

I had to back off the eq which had way too much gain. I just gave the eq's final output buffer more feedback, that's the solution for now anyhow. Now that I've fo the tranny there I probably could have left the eq stock, it would have just driven the fet harder.

I used a 2n5457. Definately has some VH vibe, to my ears anyhow. Part of that is just driving the front end a bit.

I'm wondering if I should add the series 100k at the end. That would change the output impedence and also roll off some more top. that's what the ep schematic has there anyhow.