How about a LM317 connected for constant current in the cathode instead of
the choke?
+ACI-John Byrns+ACI- +ADw-jbyrns+AEA-rcn.com+AD4- wrote in message
news:jbyrns-2702061620290001+AEA-216-80-74-90.d.enteract.com...
+AD4- In article +ADw-4401D7A4.49C8AB63+AEA-sympatico.ca+AD4-, jh.stewart+AEA-sympatico.ca
+AD4- wrote:
+AD4-
+AD4APg- Back a few months ago there was a thread wherein folks were discussing
+AD4APg- various schemes to drive a PP Amp without a phase inverter or an
+AD4APg- Interstage Transformer.
+AD4APg- Some suggested the LTP in the power stage.
+AD4APg-
+AD4APg- I've been on the run since so not sure where the whole business went.
+AD4APg- Anyway, over at ABPR is a circuit that may have been suggested, so if it
+AD4APg- was then my apologies to whoever came up with it.
+AD4APg-
+AD4APg- In this case the power OP LTP is sinked thru a choke rather than
+AD4APg- resistors or an active device. That results in a large power saving +ACY-
+AD4APg- considerable simplification of the circuit. As shown the circuit is NOT
+AD4APg- optimized +ACY- appears for reference only.
+AD4APg-
+AD4APg- The choke +ACY- OPT are in the Hammond Catalogue as their 125E +ACY- 157G. The
+AD4APg- schema show results with +ACY- without the choke in the circuit. The balance
+AD4APg- of AC plate currents is very good down to about 20 Hz. The circuits show
+AD4APg- resulting currents with +ACY- without the choke in the circuit.
+AD4-
+AD4- Hi John,
+AD4-
+AD4- Your scheme requires a large audio choke that can handle a substantial DC
+AD4- current without saturating. An equally simple scheme would be to use a
+AD4- high inductance center tapped audio choke in the grid circuit, with the
+AD4- center tap grounded and one end connected to the driven output tube grid
+AD4- and the other end connected to the grid of the second output tube. This
+AD4- scheme also halves the required drive voltage relative to the cathode
+AD4- choke scheme. General Motors here in the US used the tapped inductor
+AD4- scheme in some of their tube auto radios.
+AD4-
+AD4-
+AD4- Regards,
+AD4-
+AD4- John Byrns
+AD4-
+AD4-
+AD4- Surf my web pages at, http://users.rcn.com/jbyrns/