Comparing 2 of the same amps but find differences

[pbman1953]

I'm working on 2 of my Sunn 2000s amps. One amp has a solid state section inside the chassis and no tube rectifier sockets. The other does have sockets.

The one with the SS rectifier doesn't have the 220uf cap and resistor (1.5k) off pin 8 to ground. It has only a 1.5 k resistor. The other one does have the cap and resistor.

The schematic shows that the cap should be there

What could be the sonic difference?

[sluckey]

Make it look like the schematic. You'll have a big bass boost and you'll have less filament hum.

[pbman1953]

Make it look like the schematic. You'll have a big bass boost and you'll have less filament hum.

On it , thanks!


Another question. these 2 amps are very close to the schematic in most areas. . My first one, the one I set up to use the KT-120's , has a bit more low end than the second. Is that the difference between the older Tungsol(USA) 6550's and the newer JJ 6550's? Both sound good but the first one has more frequencies in the low end that second doesn't. Another difference is that the first one has increased storage capacitance ( 110uf) + 50uf) in the first 2 stages . The second one is close to stock values (40uf + 23uf)

[pdf64]

... Is that the difference between the older Tungsol(USA) 6550's and the newer JJ 6550's? ...

Seriously?
From what you write, there seems to be significant differences in the circuits of the 2 amps, at the input stages and in the HT supplies.
Swap over the valves in the same amp if you want to see what difference the valves make.

[sluckey]

The two circuits are different. You should expect the sound to be different. You're being too nitpicky.

[pbman1953]

Oook, maybe I am.

Once last one. Due to age, do these diodes need replacement?

In the blocked direction, with a meter on the diode setting,  they are all OL

Here are the readings in the on the output side-.573 , .566, ..573, ..578

[acheld]

Those just tested good, so no.   I generally don't replace good diodes for age alone.

[pbman1953]

Great, thanks!