I asked some questions about this a while ago, and got useful answers. I learned that my small power pentode CF will pass 25mA when loaded with a choke with a DCR of 160ohms, so all good, Now if I change to a line output transformer with a DCR of 660ohms, I understand that I need to add a negative bias supply to the bottom of the Primary, my question is, What range of negative voltage do I require to overcome the extra 500DCR, and have some adjustment for tuning, more questions to come on this little project but the answer to this one will help right now. Thanks John
Or you could apply a positive bias to the grid - still negative with respect to cathode. If the line transformer can take the DC current, great. If not, use a 160 Ohm (or whatever) resistor and coupling cap to keep DC out of the primary.
Ohms law says 500 Ohms times .025A will need an additional voltage of 12.5V that is capable of sinking the current. Given the resistance difference, is your new device happy with .025A flowing through it?
I have a similar beast running; a MOSFET-on-top cascode of a 5687 which is loaded by a bi-filar OPT in the cathode. I am quite fond of it, very clear and clean and drive any cable I attach between it and the amplifier. Bandwidth is quite nice too...
cheers,
Douglas
I have a similar beast running; a MOSFET-on-top cascode of a 5687 which is loaded by a bi-filar OPT in the cathode. I am quite fond of it, very clear and clean and drive any cable I attach between it and the amplifier. Bandwidth is quite nice too...
cheers,
Douglas