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The tube manual says that the cathode current for a 6bq5 is 65mA max. So if I want to put several of these in a row to increase power I would have to provide 65mA for every tube I use? That sure could add up in a hurry with two channels.
Edits: 09/16/14Follow Ups:
The 6BQ5 may be capable of 65 ma at lower voltages, but watch the maximum plate dissipation of 12 watts. 35ma is more normal at say 350 volts.
I measured the voltage across the 400 ohm cathode resistor and it's about 13.5 vdc at 360 vdc. Using I=E/R that gives me about 34 mA, so it looks like you are right.
The next question would be how close can I come to the 200 mA given as the mA's available on my power transformer? I would like to run 3 tubes per channel so I would be needing 204 mA if they are all the same, which I suppose is unlikely. So I guess to be safe I will have to quit at two tubes for now. That would leave some spare mAs. It's a Hammond 278x, 400v ct 400v, with separate windings for the rectifier and the filaments of the 6bq5's. The only load on the 200 mA will be the current for the tubes I think.
Edits: 09/17/14 09/17/14 09/17/14 09/17/14 09/17/14
65ma is the max for the 6bq5 but yes, if you want to parallel 2 tubes then there will be twice as much current as one if you want to run each tube the same as you were running the one. Twice the current, half the plate resistance and half the load impedance.
If you want 4 output tubes in parallel then there will be 4 times the current than just one.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Thanks for the reply Tre'. It doesn't look like I will be pulling the maximum, but I will still be limited to how many tubes I can use with the current tranny.
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