Liverpool: It's alive...HELP!!

[JoeCon]

Guys got my Liverpool finished but bloody hell something must be wrong. It has so much gain I can barely turn it up and there's feed back and crunch but almost no clean. Is that how it's supposed to be? It sounds good but out of control...

EL84's 344V on Plates 322v On screen got a 130 Ohm cathode resistor dropping 10 volts. So 76 mA for two makes it 38mA per tube. 344 minus 10 volts is 334 x .038 = 12.692 watts.

All the preamp tubes look good with the Liverpool voltage chart, nothin too crazy:
V1 168 and 144 Plates
V2 220 Plate
V3 1=207, 2=35,3=54, 6=200,7=39, 8=54

Any ideas??

[rock_mumbles]

It should clean up with the guitar volume backed off a lot ...

What are you using for a guitar?

[JoeCon]

PRS Mira with Humbuckers...

[Littlewyan]

It doesn't have any clean without turning down the guitar volume knob normally. Without the guitar plugged in can you turn all knobs onto 10 at the same time without the amp screaming at you? Bear in mind it might feedback with the speaker which is normal so dont put it on top of your speaker cabinet when trying this.

[statorvane]

It is possible the OT leads are reversed? Try disconnecting the NFB and see if it still does this.

[Bob S]

Can't see R31 1k 25w in the pics - prolly hiding.
The output tubes are running pretty hot. Bigger Rk maybe.
You could also try reducing the value of R7.

[JoeCon]

Guys

It's based on the Liverpool with No NFB or Presence just a Cut Control amd PPIMV, also no Mid just a resistor like the Rocket.

Bob, no 1k 25W the supply is based on the Fowler Rocket supply. I used that in both my Rocket and Rockster amps and it works great!!

The amps not howling like reversed OT leads but super saturated overdrive/ sustain at 1/4 volume...I like how it sounds but not at that level.

As far as turning the guitar down when it's almost off there is a bit of "clean" but as soon as I roll it up at all 4+ it like Joe Satriani on steroids!! Not what I was expecting.

R7 which is supposed to be 150K I already lowered to 100K, I'm gonna parallel another 100K for a 50K and see if that drops it down some.

Thanks....

[Littlewyan]

If there is no NFB then I imagine it would be quite mad. Even with NFB these amps have a lot of gain. Why did you leave out the NFB?

[JoeCon]

I just don't like the presence control at least from amps I've owned in the past. Maybe this one has to have one due to the gain. I can "cobble" one in and see if that helps.

But I've read of Express owners dumping the NFB and going with a cut too, and the Pool is quite the Express, n'est pas??

Also got a message saying, Tubes...go with 5751 in V1 and a 12AT7 as the PI to tame the "beast"...

[Richie]

you could make it a resonance control. Also if its a Liverpool, you can change the resistor value that goes to ground where the signal feeds to V2. if you have a 150k try a 100k or down to a 68k or use a trim pot to dial in the value you like. Then use that value resistor.

IF, you do use a feedback circuit, changing the value of feedback resistor will give you a bit more clean on the volume control. If you have a 100k lower it to a 47k or 27k, it will give you a little room on the control before the amp starts to break up.

Looks like you might want to check the pot wiring.

[JoeCon]

Richie

Yes good ideas. I will check that wiring again, did it over here and then put it all in at once. And sure don't need a bright switch!!

And that resistor is currently a 100K so I'll take that down a notch or two...

[M Fowler]

I've taken the presence control out of two Express amps and went with cut control without any problems.

I suspect a ground issue on the pots.

[geetarpicker]

I agree with Richie's tips.

These amps are quite high gain and removing the feedback loop will make it even more so. Also what taper pots did you use?

[geetarpicker]

I agree with Richie's tips. These amps are quite high gain and removing the feedback loop will make it even more so. Also what taper pots did you use?

[JoeCon]

Mark
Yes you're the guy that also doesn't like presence control. Had them on Marshalls never turned a single one...

Glen, let me check those and the grounds to them as well and I'll get back to you.

Thanks guys...