In Reply to: using cathode bias voltage for preamp tube heaters posted by DAK on July 20, 2014 at 09:36:49:
Just curious, but how could a 6550 (biased at, say 100mA) or even 2 in parallel passing 200mA at the extreme, ever pass the 600mA required to light a 6SN7? (who's heater is effectively a 10 ohm resistor). You must supply the tube heater with 600mA or it will not function right, there is no free lunch of magic current being created.
I have seen this using a 12AX7 with the heater in series passing 150 mA which will light a 12AX7 with about 12.6 volts. It is effectively a 84 Ohm resistor. Are you sure about the tubes he used?
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Follow Ups
- RE: using cathode bias voltage for preamp tube heaters - Chip647 16:59:28 07/20/14 (7)
- RE: using cathode bias voltage for preamp tube heaters - DAK 23:10:45 07/20/14 (6)
- Here you go. - Chip647 05:12:58 07/21/14 (5)
- RE: Not the one. - DAK 08:14:06 07/21/14 (3)
- RE: Not the one. - Chip647 12:20:14 07/21/14 (1)
- RE: Not the one. - jazbo8 22:10:59 07/25/14 (0)
- RE: Not the one. - drsx 12:11:25 07/21/14 (0)
- RE: Here you go. - Thomas Mayer 07:24:33 07/21/14 (0)