A new 'pool...
Moderators: pompeiisneaks, Colossal
Re: A new 'pool...
Sweeeeet, Paul - I'll bet sounds as good as it looks. BTW I love mine~! There is something about the feedback on these things that is so nice you can almost play a melody with it.
Re: A new 'pool...
This is a double post, but wanted to get it connected with my liverpool...
http://paulamps.com/FreeAir.jpg
The red arrows point to the wire that needs to be in free air.
Green arrow points to an added cap to get the coupling cap between 2nd and 3rd stages up to 7nf.
Blue arrow is the shunt resistor after the coupling cap to get the proper volume knob range. I ended up with 22K here so I could get the sweet spot of the volume knob up to ~12 o'clock. (I like the way the bright caps work when the volume sweet spot is between 10 and 1 o'clock on the pot).
I just re-read this and tried it in my liverpool and it makes a difference. Clarity is improved if the wire from the treble cap to the treble pot runs in "free air" to avoid any parasitic capacitance to the other tone wires or to the chassis. This seems to have a larger effect on the liverpool since the treble cap is only 50pf. That wire is higher impedance and is the path for all the top end of the amp, so is a key point in the circuit where you want to avoid parasitic capacitance hurting the top end.gearhead wrote:Interesting read from the Pre-Francesca days:
https://tubeamparchive.com/viewtopic.ph ... grid+noise
Jackie's second wiring scheme got him excited.
http://paulamps.com/FreeAir.jpg
The red arrows point to the wire that needs to be in free air.
Green arrow points to an added cap to get the coupling cap between 2nd and 3rd stages up to 7nf.
Blue arrow is the shunt resistor after the coupling cap to get the proper volume knob range. I ended up with 22K here so I could get the sweet spot of the volume knob up to ~12 o'clock. (I like the way the bright caps work when the volume sweet spot is between 10 and 1 o'clock on the pot).
Re: A new 'pool...
Dear Paul
That is an interesting tip. I don't think a lot of guys know the difference in tone between the 500pF treble cap and the 50pF treble cap. I suspect there are Express clone owners out there that would prefer the 50pF cap.
Regarding the coupling to the third stage, I must confess that I have always liked the 4700pF and 68K combination as it has cut and that Trainwreck insanity. I did try 56K at one stage and thought it sounded nice, but lacked that "something", what does 22K and 7nF sound like?
I imagine it would sound fatter and the gain would be more manageable.
That is an interesting tip. I don't think a lot of guys know the difference in tone between the 500pF treble cap and the 50pF treble cap. I suspect there are Express clone owners out there that would prefer the 50pF cap.
Regarding the coupling to the third stage, I must confess that I have always liked the 4700pF and 68K combination as it has cut and that Trainwreck insanity. I did try 56K at one stage and thought it sounded nice, but lacked that "something", what does 22K and 7nF sound like?
I imagine it would sound fatter and the gain would be more manageable.
Yours Sincerely
Mark Abbott
Mark Abbott
Re: A new 'pool...
Exactly. Nice FAT tone, big and round and moves the sweet spot on the volume pot up to about 12 o'clock.
But, you can't change the resistor just by itself. Reducing it will thin the tone a little since it forms a low pass filter with the coupling cap. So, the coupling cap needs to get a little bigger as the resistor is reduced.
But, you can't change the resistor just by itself. Reducing it will thin the tone a little since it forms a low pass filter with the coupling cap. So, the coupling cap needs to get a little bigger as the resistor is reduced.