In article ,
Patrick Turner wrote:
But in PP amps the B+ can be +500V and as we all know the anode swing
can be to +/-1,500V, and thus threaten to arc. There's a simple answer
which is well know and been around ever since Si diodes began to get
good reverse voltage ratimgs, and that's to connect diodes from each
end of the OPT to 0V with diode anode connected to tube anodes. I like
to use 3 x 1N7007 in series with 1M strapped across each diode to
equalise reverese voltages, and when one end of the OPT tries to rise
to more than 2 x +B, the other end tries to go below 0V so diodes
conduct, and thus the OPT voltage swing is CLAMPED. Voltage clamping
with diodes has been around for ages.
There is a schematic example at
http://www.turneraudio.com.au/100w-monobloc2-2004.htm
The amp also has Zobel networks across each 1/2 primary of the OPT to
load the OPT at HF.
There seems to be an inconsistency here, between what you said above, "connect
diodes from each end of the OPT to 0V with diode anode connected to tube
anodes", and the way the "schematic example" shows the diodes wired?
--
Regards,
John Byrns
Surf my web pages at,
http://fmamradios.com/