Mesa Boogie Question regarding tubes 400+

[groovking]

I found a box of new power tubes, mesa 454's but they are not separated into matched pairs. Will it matter with my 400+???

[Gearhead17]

Mesa 400+ requires matched pairs of 6L6's. You should call Mesa Boogie and ask them to verify, but sinced they are not matched duets, you could have a big problem.

[BassmanPaul]

Sorry but in an amp with twelve output tubes matched pairs are meaningless unless each pair has its own bias pot.

Paul

[groovking]

I guess it wasnt a bad question afterall.
Anyone else?
Ideally I would have stuck with matched pairs but then this situation came up.
Thanks All

[stjohn1299]

I'm curious about this too...I just got a 400+ with 5881s. I wonder if I get either a matched pair or matched quad of 5881s as spares, would they be fine to use if a tube ever went bad? Guess I would change out the bad tube and its corresponding match tube (assuming each front and back tube is considered a matched pair)

[Bunyo]

Originally Posted by BassmanPaul

Sorry but in an amp with twelve output tubes matched pairs are meaningless unless each pair has its own bias pot.

Paul

Hi Paul. You really think thats it not important if tubes are matched in 400+??? I got 4 tubes blown and need to chenge them. Do you guys think that it is possible to put 4 jj electronics and 8 tung sols in one power section??? Can we put different matched pairs or quads in one amp?

[Classickbass]

I had JJ's put in my 400+, but I paid extra and got 12 matched tubes. Mesa's do not have a bias adjuster from the factory so you should have your tech install a 2 pot bias adjustment as well.

[anderbass]

Originally Posted by groovking

I found a box of new power tubes, mesa 454's but they are not separated into matched pairs. Will it matter with my 400+???

If you really wanted to use those you could pay an amp tech a few bucks to match them into 2 equal groups of 6.
You'd then plug one group into the front row and the other into your amps back row.

[Bunyo]

Originally Posted by anderbass

If you really wanted to use those you could pay an amp tech a few bucks to match them into 2 equal groups of 6.
You'd then plug one group into the front row and the other into your amps back row.

So matched pairs should be put in row or opposite to each other???

[anderbass]

Originally Posted by Bunyo

So matched pairs should be put in row or opposite to each other???

Just opposite rows. The power tubes in each row of 6 are all wired together in parallel.
Check out this pic to see what I mean: http://www.google.com/imgres?imgurl=...1t:429,r:0,s:0

[BassmanPaul]

Back in the day when these amps were designed, Mesa would buy tubes and have them matched into batches that were close enough to work with each other. If you need to replace a tube you should get one that has the same characteristics as your existing tubes.

You should have the bias mod done to make the setting variable. Using two pots you can use different sextets and bias them appropriately. Using matched pairs is pointless as there in no such thing as pairs in any tube amp above 50W.