Many months ago I purchased a octal driver board to swap for my stock noval board in my ST-120 amp (purchased ~2018 I think).
I first tried a 6SN7 with a tube adaptor in the center tube, liked the results, and ordered the octal driver board. Now I finally have time to install it!!!
Anyway, I see that there are some different values in the resistors supplied with the octal board. Of course the instructions say for ST-70 all over them.
Is this due to the different B+ voltage in the ST-70 vs. ST-120, or due to the 6SN7 tubes, or what?
I know I need to move the Russian PIO caps from old to new.
Here's what I found that is notable in the resistor differences:
Resistor: Noval driver board value: NEW Octal driver board value: Notes:
R3 & R4 270k 220k Just sets input impedance? negligible
R7 & R8 7.5k 6.8k Part of the negative feedback filter?
R15 & R16 4.7k 6.8k
R19,20,21,22 30k 27k
R27 & R28 10 8.2 part of the LM334 CCS circuit (!)
R39 jumper 1k jumper I think in ST-120 for more bias; jumper again here
Should I move any of the resistors from old to new?
Thanks in advance for any insight or advice anyone can offer. I suppose I could email Roy, but I'd be interested in any opinions from the group.
I first tried a 6SN7 with a tube adaptor in the center tube, liked the results, and ordered the octal driver board. Now I finally have time to install it!!!
Anyway, I see that there are some different values in the resistors supplied with the octal board. Of course the instructions say for ST-70 all over them.
Is this due to the different B+ voltage in the ST-70 vs. ST-120, or due to the 6SN7 tubes, or what?
I know I need to move the Russian PIO caps from old to new.
Here's what I found that is notable in the resistor differences:
Resistor: Noval driver board value: NEW Octal driver board value: Notes:
R3 & R4 270k 220k Just sets input impedance? negligible
R7 & R8 7.5k 6.8k Part of the negative feedback filter?
R15 & R16 4.7k 6.8k
R19,20,21,22 30k 27k
R27 & R28 10 8.2 part of the LM334 CCS circuit (!)
R39 jumper 1k jumper I think in ST-120 for more bias; jumper again here
Should I move any of the resistors from old to new?
Thanks in advance for any insight or advice anyone can offer. I suppose I could email Roy, but I'd be interested in any opinions from the group.