Svetlana 6L6 Bias BDRI

[JMP/HBE]

Re: Svetlana 6L6 Bias BDRI

Yep, I'm a ABB fan boy. love em. All eras.

This is the reason knowing your plate voltage is helpful.

If it's 455 then the math is:

30 (watts plate dissipation of 6L6GC)/455 = 66ma (100% plate dissipation current.) 46 ma = 70% plate dissipation. 70% is considered the high end of safe and many like it there. Therefore many techs set it there.

If it's 475 volts however:

30/475 = 63ma. 46 ma = 73% PD. It might not be red plating but it is getting beyond the safe zone. It might have shrill highs and muddy lows too.

If it is 410 volts as reported in some articles:

30/410 = 73 ma. 46 ma = 63% PD

You're just guessing his PV. Plus he said his tubes were "orange". Tubes properly biased @ 70% idle are not "orange". The plates should be nothing but the color of the metal grey or black. We can guess all day long what his bias "should be" but until someone sticks a meter on it we will never know. This thread is pointless.

Bias for an amp is set in relation to plate voltage & the wattage of the tube via a mathematical formula. There is no guess work or hypothesis involved.

 

[Lake Placid Blues]

Re: Svetlana 6L6 Bias BDRI

I told him he needs to know the plate voltage of his amp, and provided examples why. I did not guess the plate voltage of his amp.