Hi gents,
I want to ask you for any idea how to solve this problem:
Volume knob is closed but there is the signal of the guitar like at vol. 9 o´clock, thats more than bedroom level.
I changed Vol Pot, reduced layout to shortest possible cable, every tube has its filter cap right before (no cable lenghts).
No parallel cables.
Every B+ cap has a propper grounding, so this is not the reason.
So until 9 o´clock on Volume there is a steady clean signal than the pot brings the regular signal in.
With vol closed the crosstalk signal gets no influence of the tone stack knobs BUT the presence!
Therefore I think the grounding is bad, allthough its close to the original. Close therefore because its not on the back of the pots but it begins with B+3 cap - 33µF, than presence, 3rd stage - B+4 cap 22µF, Mid,1st stage - B+5 cap 22µF, Volume, Entrance -Ground.
I should give PI (Presence) and (I forgot to mention) PPIMV together to the grounding point of poweramp - the cathode of the 2 EL84 (PPIMV is allready there).
That means power- and preamp has its own grounding point. Than the crosstalk should be reduced to a minimum if it comes through B+ line.
Am I right with this thoughts?
Best
Hans-Jörg
Crosstalks in Liverpool 18W (2xEL84)
Moderators: pompeiisneaks, Colossal
Re: Crosstalks in Liverpool 18W (2xEL84)
Schematic? You have some mixing resistors if using multi channel volumes?
Re: Crosstalks in Liverpool 18W (2xEL84)
You write that you changed the volume pot, but have you ever MEASURED the value/taper of the volume pots? You may have two volume pots that are doing the same thing - not going to zero.
Re: Crosstalks in Liverpool 18W (2xEL84)
Hello,
thank you for your inputs (all pots were ok).
BUT I found the reason:
it was a TAD ecc803, a long plate tube for V1. I was afraid she will be microphonic because of her long plates, but this wasn´t the case.
But both triode systems been coupled intern. Liverpool and Express are high gainer and sometimes very noisy.
So this long plate system of the ecc803 (which is close to the old 12ax7 Mullards) supported the intern crossover.
Very simple, but it tooked time for me because I don´t wanted beleave that this very good tube can cause this.
In every other amp (Dumble, Fender, etc.) its a very fine tube but not with a Liverpool!
Best
Hans-Jörg
thank you for your inputs (all pots were ok).
BUT I found the reason:
it was a TAD ecc803, a long plate tube for V1. I was afraid she will be microphonic because of her long plates, but this wasn´t the case.
But both triode systems been coupled intern. Liverpool and Express are high gainer and sometimes very noisy.
So this long plate system of the ecc803 (which is close to the old 12ax7 Mullards) supported the intern crossover.
Very simple, but it tooked time for me because I don´t wanted beleave that this very good tube can cause this.
In every other amp (Dumble, Fender, etc.) its a very fine tube but not with a Liverpool!
Best
Hans-Jörg