14 Mar
2013
14 Mar
'13
3:16 p.m.
Then I spoke with a guitar tech about using 12AX7s, I
think it was, in
guitar effects, and was wondering where they got the high voltage. He
told me B+ in such circuits is, IIRC, 12V. It makes sense - power
delivered is not really a consideration in such things - but it was a
bit of a surprise to me....
A low anode volatage is likely to cause distortion at quire moderate
signal nlevels, which might be an advantage for that application.
Certianly you cna run some, if not, most small signal valves at low anode
votlages 912V or 24V). Power tyoes are non-starter, although I have heard
of people using TV line output valves ('sweep tubes'?) with a 12V anode
voltage to drive headphones.
Philips made a few 12V anode types for car radios (with a single
transitor as the audio outpu stage) that were known to be selected
versions of more nornma, types (ECH83 -- ECH81 nad EBF83 -- EBF89 IIRC).
Other companies made similar valves, including soem where you applied a
+ve voltagr to the first grid to act as an acceleerator.
-tony