resistors I think
The big can with writing on is a 4uF capacitor, from the size I assume it’s oil filled?
Yes, they’ll likely have been trying to preserve the rectifier.
If it uses a circuit like the one Pete linked to but with an E80CC it is still going to be pretty high gain on that line stage.
Yes:
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Guess my question is has this been taken away from the design so much that it is no longer an M7.
It sounds fantastic but I don’t want to have a shit show when I (inevitably) sell it.
Not really sure what an M7 is, there were so many variants. (at least 6 I know of including this one). The neat trick is that they share the character.
Cathode follower. No gain!
Doesn’t the gain come from the first part?
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Oh, sorry, yes. Was looking at the last device.
I guess E80CC is at least lower than a 6072. But yeah, still excessive.
Needs output transformers rather than a CF! Lose some gain that way as in M10/L300 
Yeah, but more expensive.
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12BH7 would get it lower provided the values of anode & cathode resistors are suitable.
I guess you need to check first that the E80CC are the quietest of samples.
I suspect the 12BH7 might have been what was in it originally.
Maybe but I don’t think they are as tall & the wire clips seem to match the height of the E80CC.
I always thought they were quite tall, but yeah, perhaps not as tall as the E80CC. The clips are easy to change, just a bit of copper wire soldered to tags.
GE 12BH7 is 67mm tall and the E80CC I have is 80mm
Have you got any 12BH7?
How quiet is this pre when volume is at minimum?
Nope haven’t got any 12BH7s
With the volume at min I can clearly hear a hum and hiss from 12 ft away, similar sort of volume to when you are standing near power lines in fog/mist.
The hum is constant but the hiss only increases when I get up to around 1/2 way on the volume.
Turn one of the power amps off & pull the interconnect to it out of the back of the M7. Does the other speaker now still have hum?
Yes
And same result if I do the same with the other amp.