1960-1962 but a couple of people on other BBs have gotten me going on this.
Reply #1; from the Weber BB as follows:
"As it stands now, your preamp tube is "grid leak biased", these typically don't like big signals. Convert triode B to cathode bias. Disconnect the ground reference from cathode B and add a 2.2K resistor to ground, bypassed by a 10-20uf cap. Relace the 10meg grid leak resistor with 1meg, replace the 0.01uf input cap with bare wire, you plate voltages may raise by 10-15% on this triode, it just comes with the territory." But the reply didn't include a reference to A, I prompted, and the reply was: "try a 1K to 1.5K cathode resistor at A? 20-50uf bypass cap, no bypass cap at all tends to make things cleaner. As with triode B, lose the input cap & use a 470K to 1Meg grid load resistor."
Reply #2; from the Hoffman BB as follows:
I said: The cathodes are currently jumpered together as shown but I intend to separate them, add 1.2K cathode resistors to both and bypass the cathode resistor in A with a 25uf/25V cap and a .47 in B (chosen because I happen to have one) but only if .47 is large enough to make a noticeable difference compared to nothing at all.
They said: "Connect your cathodes as you stated. Connect the grids like this..."
The most significant difference in the replies are the one suggest a 'straight wire' in where the other says a 33K. Nearly every other Gibson has a 56K-82K resistor there; the rest of it is (unfortunately) elective. Different values giving subtly different flavors.
Based on what these gents had to say, this is what I think I'll be trying:
I want a distinction between bassy, browner, darker, GA8/GA18 tone in 'Juan' and brighter, edgier, more sizzle in 'Coastie' ... his Silvertones use 2.2K cathode resistors w/o bypass caps. Don't want to re-invent anything, just get different basic tones. Both amps did not have cathode bypass resistors on the final 1/2 gain stage, now they do ... they are getting there.
Reply #1; from the Weber BB as follows:
"As it stands now, your preamp tube is "grid leak biased", these typically don't like big signals. Convert triode B to cathode bias. Disconnect the ground reference from cathode B and add a 2.2K resistor to ground, bypassed by a 10-20uf cap. Relace the 10meg grid leak resistor with 1meg, replace the 0.01uf input cap with bare wire, you plate voltages may raise by 10-15% on this triode, it just comes with the territory." But the reply didn't include a reference to A, I prompted, and the reply was: "try a 1K to 1.5K cathode resistor at A? 20-50uf bypass cap, no bypass cap at all tends to make things cleaner. As with triode B, lose the input cap & use a 470K to 1Meg grid load resistor."
Reply #2; from the Hoffman BB as follows:
I said: The cathodes are currently jumpered together as shown but I intend to separate them, add 1.2K cathode resistors to both and bypass the cathode resistor in A with a 25uf/25V cap and a .47 in B (chosen because I happen to have one) but only if .47 is large enough to make a noticeable difference compared to nothing at all.
They said: "Connect your cathodes as you stated. Connect the grids like this..."
The most significant difference in the replies are the one suggest a 'straight wire' in where the other says a 33K. Nearly every other Gibson has a 56K-82K resistor there; the rest of it is (unfortunately) elective. Different values giving subtly different flavors.
Based on what these gents had to say, this is what I think I'll be trying:
I want a distinction between bassy, browner, darker, GA8/GA18 tone in 'Juan' and brighter, edgier, more sizzle in 'Coastie' ... his Silvertones use 2.2K cathode resistors w/o bypass caps. Don't want to re-invent anything, just get different basic tones. Both amps did not have cathode bypass resistors on the final 1/2 gain stage, now they do ... they are getting there.