What’s the typical plate voltage?

[snakej200]

I’m just curious what’s normal. Seems every amp I have leans toward low. Figure all of these values at 35ma bias give or take (measured with eurotubes bias pro)

1975 super lead - 430
1996 jcm slash 2555sl - 426
1959slp reissue - 420

I’ve also got a headfirst Alta 100 and it’s been a while since I biased it but I remember the plate voltage was under 450, maybe around 440. I read about all these amps at 460-560 plate voltage. Half of my tube stash I can’t get biased properly (the bias pot maxes out well before I can bias them to 60%) and it just dawned on me that if my plate voltage was say 480 in my 75’ super lead then all my el34’s would be in range as opposed to certain quads.

 

[Jon Snell]

The HT on the anodes is a little meaningless as that depends upon your mains voltage, bias setting and valve type. Plus any changes in smoothing capacitor/choke values.
To set the bias, measure the HT on the anodes and measure the current flow through watever means you wish, you can then use mathematics to work out the dissipation.
The best data, as far as I can tell, is the history of the evolution of the marshall super lead, a youtube video by Johan Segeborn. He covers the design changes.

 

[matttornado]

I get 480 w/ my 1974 Superlead.

 

[william vogel]

I’ve got 475 on my 1971 Super Lead.

 

[Pete Farrington]

Context is everything; for any of the voltage readings so far to be useful, we also need to know the actual measured contemporaneous mains voltage being supplied to the amp, and the amp's mains voltage setting.
A reading made at a different time is irrelevant.