Ian Iveson wrote:
"Patrick Turner" wrote
RDH4 says +/- 10%. ...
Brimar says mains-derived heater voltage should be within 5% at
nominal mains voltage, as long as mains itself remains within 10%
Does that mean 15% is the limit?
I can't quote the exact reference from RDH4, but its in there alright.
And there is no mention of +/-15% afaik.
So whatever that book says is about right.
I try to make the heater voltage for all gear stay within +/- 2% of the
official proper voltage.
Mains might vary +/- 5%, but I have never seen more than
between 235v and 253v for 240v nominal, so I guess heater voltage would
vary say +/- 7%, but over time its not enough to significantly shorten
expected tube life.
One can place 12.6 volts onto a 12AX7, and gee it looks bright, but not
for very long,
and you might stuff the emission of the cathode....
The tube will also work with 8 volts on the heater, but it'll be noisy,
and Gm will be low...
Patrick Turner.
cheers, Ian
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