[shafu]

Question on making tubest last longer:

Would it make sense to rotate the tubes in my MPX3? I think the tube to the right is the output tube? Looking at my amp last night, it looks like the tube on the right was burning brighter than the other two. Also, the black/silver color inside the tube seems to be more in that tube then the others as well. Does that tube burn hotter? If so, should I rotate the tubes (ala tires on a car) to get even wear?

 

[fredpb]

Leave them. They are ok.

 

[ServinginEcuador]

Sun,

In a nutshell, yes, tubes can wear unevenly. Every tube that comes off the assembly line could have a very slight difference that would make it wear slightly faster than the next one. That's part of the game with tubes. The Syl Gold Brand 5751 can wear out MANY times faster than other 5751 tubes due to the metal used.

Is it something to worry about? I don't think so. So what if one tubes wear out as much as 5% faster than the other. It won't make much difference since they will both start sounding bad about the same time anyway.

If you are concerned about this at all, email Mikhail to see if the tubes are biased differently and can stand to be swapped at some point so that they wear more evenly. Only he knows since he built the thing, so drop him a line and see what he says.

 

[Rameish]

Tubes can and do wear out unevenly. However the brighter tube you're experiencing is most probably due to more of the filament being exposed (nothing to worry about IMO). If there is an uneven glow (switch of the lights at night to check with hot spots (red orange) on the glass/bottle then you have a bad tube).

All in all it sounds scary but really isn't - unless you buy your tubes from less then reputable vendors on ebay.

 

[Guild]

So what is meant by "matched pair"?? Does it have to do with actual sound or how much "life" is left in each one? Technical explanations welcomed.

 

[ServinginEcuador]

Matched pair is just what it wounds like: a pair of tubes are matched so that their gain, amplification of the audio signal, is closely matched so that both the left and right outputs are close to equal. If the two tubes aren't matched it would drive you nuts when listening since one driver/speaker would be consistently louder and throw off the soundstage and balance of the sound toward one side of teh soundstage or the other.

 

[Mastergill]

Quote:

Originally posted by ServinginEcuador Matched pair is just what it wounds like: a pair of tubes are matched so that their gain, amplification of the audio signal, is closely matched so that both the left and right outputs are close to equal. If the two tubes aren't matched it would drive you nuts when listening since one driver/speaker would be consistently louder and throw off the soundstage and balance of the sound toward one side of teh soundstage or the other.

Well, in fact the main purpose of matching tubes is for running them smoothly in a push-pull design. If you have single ended design or preamp stage, you don't really need to have matched tubes to work good or for L/R balance.
Also if you have bias adjust for each tube in push-pull design you don't need matched tubes.
But like you ServinginEcuador, i like the idea of having both channel perfectly balanced