Tube Bias Point

beaner

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i just got a new set of JJ 6V6 tubes and they are marked with a 30 on the boxes and have a sticker on the base that says bias point 30. Does this mean the tubes will preforme the best with my amp biased at 30ma/mv? My superchamp xd im putting them in has a stock bias of 40mv or ma i don't remember the exact measurement its 40 something none the less. Does this mean when i get ready to bias the amp i should set it to 30 and not 40 to get the best tone out of the tubes? I'm kinda new when it comes to this stuff so any help would be appreciated i tried google and couldn't find much other then explaining what the bias point is on a tube.
 

qpHalcy0n

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The number is a relative grading number applied by the supplier. It's relative because it will tell you where the tube reaches full bandwidth at 400 plate volts. This is RELATIVE and not specific to your amp. Like Groove Tubes number system and Mesa's color system.

If Fender says 40, then you would want to bias to 40 regardless of the tube manufacturer.

The method that your amp uses to check bias is relatively safe provided that you follow certain basic safety guidelines. It does not require you to probe any high voltages or anything. That said, again, it will require you to be probing around the circuit board with your multimeter as probes can slip, your fancy watch might discharge a cap right to your hand, etc etc... There's probably a sticky here somewhere.

Are you familiar with the method of bias for this amp?
 

beaner

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yea i have done it a few times im pretty comfortable doin it now the first time i had my wife sitting next to me with a phone in her hand with 911 pre-dialed. hahaha i was freakin balls

I just wanted to make sure that number didnt mean anything important to my amp.
 

qpHalcy0n

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No, bias to your amp specification.

Now, further down the line if you buy from that dealer again and you buy tubes with that same number on them, there's a good chance you won't have to re-bias the amp. Always check anyways, though.
 

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