Valve Data confusion.

[John Caswell]

Hi all,
As the cathode of the top valve is is elevated "X" volts above earth and possibly the heaters are earthed, it would be a good idea to elevate the heaters so that you do not exceed the mfrs heater cathode rating. I suggest halfway between the upper cathode voltage and the lower cathode voltage, implemented like the Phono II/ III. Remember to decouple it with a suitably rated elco capacitor

John

[pre65]

Bob, has the heater transformer got a centre tap ?

[bob orbell]

Originally Posted by pre65

The MJ article does not mention raised heater potential.

Are your heaters raised potential Bob ?

Yes Philip they are, I am using two WD PSU III's one for the Phono @ 250 and one for the Pre @ 285 so both have elevated heater supply's. BOB

[bob orbell]

Thank you all for your comments, John,Philip, see my post no. 13. BOB

[pre65]

I can't remember what volts were added to lift the heaters on the Pre3, is it enough ?

[bob orbell]

Yes Philip it is, the cathode will sit about 200v above ground, I think all the information about that is in the FAQ, Pre II conversion to CF. BOB