Express Values pots and Presence controls in a Liverpool

[RJ Guitars]

I have been working with a guy to clone his original Liverpool amp. I believe it was one of the later ones and curiously, he has the same pot values and presence control circuit as is used in most of the Express amps I've seen. This was somewhat gratifying to me because I have been using the Express presence control in all my half power Liverpool builds the past couple years.

I got to see gut shots of it (sorry he doesn't want those to be posted) and it looks almost the same as any of the other LP's we've had a look at here at TAG. If you compare this amp to the other Liverpool's gut shots around the web you'll find that KF was somewhat OCD about bending every component lead and making every wire path just the same...

Maybe this is nothing new to some of you, but I had not seen it before. Since this is likely a later version of the Liverpool, I am curious if it was just a matter of convenience or really significant that the Express values were used? The volume, Bass, and Treble pots are 1 Meg Audio, the mid is a 25K (he also wanted an audio taper pot here but wasn't absolutely sure it wasn't linear), and a 5K presence pot. Otherwise the board values seemed to match up pretty close to what has been published as correct here on the TAG forum.

[fishy]

RJ,
I seem to remember noting this from a post from Allynmey where he mentioned using the Express setup. Can't find that now though.

My last Liverpool build used the Express setup and I was happier with it over the DC free setup.

[fishy]

Found it........
I might have to look at my last 'pool again and see what I did on the TS too.

http://ampgarage.com/forum/viewtopic.ph ... ce+express

[RJ Guitars]

Yeah, it kinda sounds like the same item... too bad more of those guys didn't stick around.

[Reeltarded]

It sounds more open even when you turn it down on a Marshall.

I hate the 25k circuit. ooo

[RockinRocket]

If this was a later build any chance it had any Pec pots in it RJ?

[RJ Guitars]

If this was a later build any chance it had any Pec pots in it RJ?

Nope... not sure what they are because I haven't studied these beasts to an extreme level but it has the buss bar soldered to the back of it and they don't look similar to PEC's. They are also the type that have a small recessed circle in the back and he has folded back the grounded tabs on the pots and soldered them to the housing as well.

[Mark]

The 5K presence pot versus the 25K presence pot isn't limited to Express and Liverpool amp, this sort of thing first raised it's head when the Fender brown face amps surfaced.

The problem with the 25K pot is the taper, if it had a reverse taper of sorts we would feel differently about it.

A 50K reverse log pot is all that is available, so when it is all said and done the 5K pot is the best option if you can put up with a scratchy pot. which we can now as opposed to people thinking the amp was faulty in the fifties.

It isn't a big deal in the scheme of things.

[martin manning]

Hi Mark, There is more to it than the pot taper- the response is different. The silent type cuts more midrange frequency feedback for the same reduction in high frequency feedback at intermediate settings, and it doesn't get the cap completely out of the circuit at the extreme CCW setting.

[Ron Worley]

Yeah, it kinda sounds like the same item... too bad more of those guys didn't stick around.

RJ, if you were including me, then I'm somewhat back- job issues, some moves, etc. pretty much pushed me off amp stuff for about 6 years. I'm trying to work back into it. Updating the TW docs was just not possible from a time perspective.

[Mark]

Thanks for the reply Martin, I appreciate the feedback.

[kwijabo]

interesting about the pots, RJ, and thanks for sharing. it should be no surprise that each amp could be different. i've never seen the inside of a real one in person. so i'm left with 4 pics from the net.

1 & 2:
http://ampgarage.com/forum/viewtopic.ph ... 331d641378

in the shot with the mica's, it looks like the tone stack and phase inverter mica's are the same size, so probably ~50pF. i can't tell if it is the angle or really the way it is, but in the shot with the blue caps, the tone stack cap does look fatter. so perhaps that tone stack is the express style 500pF. for both you can't tell for sure but it looks like it could be the express presence circuit. no idea about tone pots.

3:
in the gutshot that was on dave funk's site, it looks like the pF caps are the same size, but the the treble and bass pots appear to the be the same. so either just the same series or the same series and values. presence circuit is the non-DC type. this pic has since been removed from his site, but its elsewhere.
http://www.tubedrive.ru/wp-content/uplo ... good_7.jpg

4:
the ginger clone looks like it has 500pF in the tone stack, but the treble and bass pots look different. non-DC presence.
http://users.zoominternet.net/~jdhall/amps/DSCN0914.JPG

i guess the best way to decide is test them all out and see which sounds best. sounds like this winter's project!

[RJ Guitars]

Yeah, it kinda sounds like the same item... too bad more of those guys didn't stick around.

RJ, if you were including me, then I'm somewhat back- job issues, some moves, etc. pretty much pushed me off amp stuff for about 6 years. I'm trying to work back into it. Updating the TW docs was just not possible from a time perspective.

Hey Ron, glad you found your way back. A lot names and faces have changed but basically it's still the same fundamental study and discovery of the four or five basic Wreck amps and the subtle variations that we have discovered or rediscovered. It's getting harder and harder to find most of the original NOS parts but there has also been some great discovery of good sounding replacements. We have more choices than ever before in transformers and we've managed a few more looks inside some originals to learn of a few variations that KF made along the way.

Good to hear from you, looking forward to your build reports.

rj