"Scott Dorsey" wrote in message
...
In article . com,
wrote:
I'm wondering what nasty effects i can expect, if any, for exceeding a
tube's maximum heater to cathode voltage rating. the tube is a 6072,
and it's maximum claimed voltage is +- 90v peak. i'm using one triode
as a cathode follower, and so the voltage at the cathode is gonna be
around 150v above ground. i'm running AC on the heaters.

Depending on the tube, it could be anything from hum to premature heater
failures.

I've even seen some odd distortion behavior and oscillation.

so, why not cap couple before the follower you say? well, some think
even the expensive caps sound better when driven and loaded with lower
impedances. i'm saving the cap for the follower's output.

So, raise the heater reference voltage. Hang the heater at +150V.

If you're limited to a single heater circuit for all the tubes, float it at
+75V. That'll mean the non-CF tubes will be at about -70V H-C and the CD
will be at about +75V. Everyone should be happy.

Peace,
Paul