Biasing help

[Joshabr1]

The method above is very accurate and very simple. Fairly safe if your competent inside a tube amp. Only way to do it.

[Jeremy1283]

Tonight i ventured into unknown territory and tossed the resistors to ground. I would have to say it changed my tone in a pretty big way. The amp has way more high end. I can't believe how much different it sounds.

[jnew]

Wow, you are really going for it here, I think it's great! Here is Robert explaining how to do it:
http://forum.metroamp.com/viewtopic.php?f=28&t=23950&
So after you read Robert's post, here is how I do it. I love this method. First put a buss wire where the 1ohm resistor used to be on the power sockets. With the amp turned off, I measure the resistance of the OT between the HT fuse (or center tap) and pin 3 of V5 and V6. You will probably get from 13 to 17 ohms one either side. If you get say 15ohms at pin3 on V5 and 17 ohms on pin3 of V6, use the V6 reading for the formula. Now turn the amp on and measure the plates. With the amp still on put your multimeter probes back onto the HT and pin3. Watch out because you have some very high voltages on those probes, it is best to use alligator clips here. Formula: 17.5(typical el34 or 6ca7 dissipation) decided by plate voltage X 17(this number is the OT's resistance you measured) X 2(for 100W amp, but for 50w amps don't multiply times two) = target number. with the plates around 410 you should get a target number of about 1.5 volts at pin3 V6 or V5 with the formula. Keep rechecking the plates and adjusting the formula because they change a bit as you bias. Try biasing beyond the target a bit say 2.0, or try biasing slightly colder to see how that sounds.
Neikeel posted this in another thread, it's a good read:
http://www.aikenamps.com/index.php/the- ... on-biasing

I'm lost here. I've got 322 at the plates and my highest measurement was at 16.8 between the OT Cntr Tap and the HT. My math tells me my target is .91. Where do I measure this at?

[axeman]

Try it like here.
http://www.marstran.com/50W%20Bias.htm

[Strat78]

17.5/322=.054 X 16.8 = .91 X 2 = 1.82

1.82
This is for the 100w amp right.
Measure from pin3 to HT fuse while amp is on, be careful!

[jnew]

Shit, forgot all about this thread. OK, so only using two tubes. .91 is what I'm looking for, right? Like a 50 watt.