Power tubes, help!!!

[salvatruco]

I been trying different power tubes on my amp (Traynor YCS50H), and there is one match set that I like.... the question i have is: I am would like to bias this power tubes to 82 mV ( traynor recommend to bias anywhere between 65 to 85 mV). the match power tubes have a difference of 10 mV between tube, in this case if i want to bias the amp to 82 mV should i take the average between the two tubes to reach 82 mV???? any help would be appreciate it.

thanks,

p.s. the amp only has one trim pot to adjust the bias

[skipm45]

Here is some information on biasing. Hope this helps

http://www.diyguitarist.com/GuitarAmps/PT-Biasing.htm



Skip
www.skipzcircuits.com (http://www.skipzcircuits.com)

[Blue Strat]

I would set the highest one for 82 (that's 41mA for that tube). Any higher than that and you might be risking killing that tube.

Trust your ears. There's nothing magical about any particular bias setting as long as it's within the acceptable range.

[salvatruco]

I would set the highest one for 82 (that's 41mA for that tube). Any higher than that and you might be risking killing that tube.

Trust your ears. There's nothing magical about any particular bias setting as long as it's within the acceptable range.

Thanks for the replied, (traynor YCS50H recommends to bias anywhere between 65 mV to 85 mV) I was running the lower one at 82 mV so the highest one was running at 92 mV. I followed your advise to lower the highest one to 82 mV and for sure , there is a difference in sound wich i am not really happy about... but at the same time, I do not want to overload anything in the amp..

thanks

[Blue Strat]

Thanks for the replied, (traynor YCS50H recommends to bias anywhere between 65 mV to 85 mV) I was running the lower one at 82 mV so the highest one was running at 92 mV. I followed your advise to lower the highest one to 82 mV and for sure , there is a difference in sound wich i am not really happy about... but at the same time, I do not want to overload anything in the amp..

thanks

Hold on. You're saying that EACH tube is running at 65 to 85? That doesn't sound right. I thought you were talking about combined current for both tubes.

Unless this amp has a VERY unusual bias monitoring setup you shouldn't be above about 40mA per tube.

[salvatruco]

Hold on. You're saying that EACH tube is running at 65 to 85? That doesn't sound right. I thought you were talking about combined current for both tubes.

Unless this amp has a VERY unusual bias monitoring setup you shouldn't be above about 40mA per tube. Yes, I was talking about the combined current for both tubes. :AOKI meant "traynor recommend to adjusting the zero signal bias to 75 mV +/-10mV DC at each of the test points".
:)

[SLG]

I've done a lot of amp work and building over the years. When I adjust the bias in an amp, I simply adjust the bias by ear. I never adjust the bias to a particular number setting. I do connect a bias meter, but I don't even look at it most of the time. I adjust the bias to the point where the amp sounds its best. Once I get to that point, I check the meter to be sure I'm not exceeding the maximum current. That's it. Find the maximum recommended current for your voltage and tubes. Use that number as a "not to exceed" point in your adjustment. Anything less, as long as it sounds good to you, is fine.

[donnyjaguar]

I generally bias up the top-end for hi-fi but stay lower for MI amp's. If you bias hotter you generally put the tube into a more linear range, which is great for sound reproduction. Sound production on the other hand is a different story. The amplifier becomes part of the instrument so in this case SLG's approach is probably better.

[salvatruco]

thanks everyone for your help!! I'll be checking with traynor in regards the plate volts on this amp..

thanks

[Blue Strat]

I've done a lot of amp work and building over the years. When I adjust the bias in an amp, I simply adjust the bias by ear. I never adjust the bias to a particular number setting. I do connect a bias meter, but I don't even look at it most of the time. I adjust the bias to the point where the amp sounds its best. Once I get to that point, I check the meter to be sure I'm not exceeding the maximum current. That's it. Find the maximum recommended current for your voltage and tubes. Use that number as a "not to exceed" point in your adjustment. Anything less, as long as it sounds good to you, is fine.

Excellent advice. As with all good advice, though, people will ignore the more difficult parts (like checking the max) and focus on the easy parts (listening). Some people will like the way an amp sounds when it's way beyond the max. I would have worded this to say "find the high point listen, and adjust downward until you find the sweet spot". ;)