I'm building my LP, and I noticed on the Layout that Tim and I worked on shows the wiper of mid and bass pots wired to the right most lug of each respective pot.
The Express is not wired this way for sure and I can't see clearly enough in Allyn's pictures to tell.
I looked at the schematic and it's not clear- because there are no little black donuts where the wiper crosses over the input lug. The Express is drawn completely differently with the one lug unconnected.
I had thought that the LP preamp was identical to the Express... but maybe Ken did it differently to voice the tone stack for the EL84 output stage????
I built my LP based on the layout sticky and I noticed that it differs from both the Express layout as well as Ceriatone layout. Probably explain I have read people say their amps are too bright and non-interactive tone circuit. response. I am going to open my LP backup and try some things.
On the tone stack I guess you're right Pete.... but from an anal builders perspective it is different. Allyn's replica has them unwired to the wipers...
OK, the plot thickens-
I was going to wire up the presence pot and noticed that the layout does not jibe with Allyn's build pics (see below)
The layout shows the wiper and left most lug connected, but Allyn's amp has the left most lug instead wired to ground. Something is amiss here, me thinks.....
Allyn??? Dana? Anybody???
Ron
You do not have the required permissions to view the files attached to this post.
I have mine wired per your layout, not the Ceriatone layout. Bottom line is I am leaving them the way they are. The more I play this amp the more "right" it sounds. I just need that damn 4x12 to get here. I'll give it a shot this weekend and disconnect the outer wipers on both Mid & Bass.
On my Liverpool I get the following response from the controls:
BRIGHT: Like the 100pf but can use the 500pf. Adjusted based on speakers & cab.
VOLUME: Not really a volume, more like a gain/saturation control. Anywhere betwen 10 o'clock and 2 o'clock is the sweet spot.
TREBLE: A little gives you a lot with this one. Have this one normally around 2:30
MID: Interacts with the BASS pot. More left I get more pronounced bass, less mids. More right a little more treble & more mids. I keep this at 1:30, about 1 setting less than the TREBLE.
BASS: Lots of bass here. I like it about 9 o'clock
PRESENCE: Yep, it does the presence really well. Right now it's at 12:30.
Another note, when I turn the mid to 0 and the bass & treble all the way up it's that classic mid-scoop sound. Reminds me of a Matchless Lightning scooped sound. I also like to dime all the controls and adjust the volume to about 11 o'clock then play withthe volume & tone on the guitar.
The cap is connected across to the presence pot differently. These differences look to be represented in the schematic.
On the Express the cap is between ground and the wiper. The remaining lug is the connection for the feedback resistor. The cap probably connects to ground directly on the buss.
On the Liverpool, the cap is between the other side of the pot (25k) and goes to the wiper. You also have the tail resistor in there. The feedback is coming off the tail of the LTP.
The pot values are also different.
The Liverpool should not be scratchy with the cap protecting the pot from DC unlike the Express ( think I have that right)
It looks like Allyn used the 'old' style Presence (when I say 'old' style I mean Marshall old style with the 5k pot...these two different ways of doing the Presence are both straight up Marshall...I'm not sure when Marshall switched from old scratchy style to the newer '25k' style). I didn't even know that KF used both. I don't see the 4k7 resistor in that pic of Allyn's amp so that's why I assume that.
When I look at the layout for the Liverpool in the files section it doesn't look right. The left lug of the Presence should be grounded.
There are different ways to connect it all up...some stuff doesn't matter. If you're just using a pot as a variable resistor to ground then it doesn't matter which lug is grounded and which is the 'hot'...you get the same resistance value to ground (and the same taper) either way. And if it's in series with a cap it doesn't matter whether the cap is 'first' or the resistor is 'first'...UNLESS that cap is blocking DC (it still won't matter but most people like to keep high voltage off the pots...whenever possible/convenient).
Last edited by Fischerman on Wed Nov 26, 2008 1:43 pm, edited 2 times in total.
I'll just use this dbl post to add this: IMO/IME, when you use the 25k pot style Presence...the pot is too big relative to the 4k7 resistor. So the pot isolates the cap a little too much and the Presence control might not do much until it's turned up a bit. I think Marshall used a 25K pot because they already used that value for the Mid pot and already had it on hand (it's less efficient to have to order another value pot just for one control). So you can experiment with a resistor in parallel with the 25k pot to get a better response.
Or maybe you like having a lot of control on the 'lower' end of the sweep (which certainly could be the case with bright-ish amps) in which case leave it at 25k.
I'll just use this dbl post to add this: IMO/IME, when you use the 25k pot style Presence...the pot is too big relative to the 4k7 resistor. So the pot isolates the cap a little too much and the Presence control might not do much until it's turned up a bit. I think Marshall used a 25K pot because they already used that value for the Mid pot and already had it on hand (it's less efficient to have to order another value pot just for one control). So you can experiment with a resistor in parallel with the 25k pot to get a better response.
Or maybe you like having a lot of control on the 'lower' end of the sweep (which certainly could be the case with bright-ish amps) in which case leave it at 25k.
I've wired them both ways and done listening tests and I do not like the 25K Liverpool sound nearly as well as the Express layout. $.02. Same goes with the open ended tonestack on the Express compared to the interactive Liverpool. I like the Express stack tonally. $1.00
The Last of the World's Great Human Beings
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Finally getting back to my Liverpool build after a long hiatus and came across the newer layouts. Tonestack (bass/mid) difference got my attention.
As fishy also pointed out, I can't tell any difference between the two electrically. If the bass and mid right (upper) lugs are soldered to the wiper, that's just a short circuit. Completely bypasses that portion of the pot between the wiper and (right) upper lug. Same thing if you just leave them hanging free.
Have already done the tonestack wiring (lugs soldered) and am a bit reluctant to cut and bypass at this point if it doesn't make sense.
