Tubes and speaker magnets?

[Joe E]

I just replaced the speaker in a small combo amp (Music Man RD 65)with a speaker with a much larger magnet. The magnet is maybe another inch or two closer to the power tubes. Will this have any effect on them?

The two EL..tubes have a shield in front of them between the tubes and the main frame of the speaker.

I ask because it almost sounds like the amp breaks up sooner than before. This is not the speaker, because I disconnected the speaker and used an external cabinet and it breaks up sooner on it as well. And did not before.

The only other thing I can think of besides a machanical issue (IE Magnets too close to tubes) is that the amp was turned on and sounded clean with speaker number 1 (but had a frap at loud volumes). THen I replaced the speaker (#2) and turned the amp back on. IN the second case the amp was on much longer and the tubes were therefor on longer.

Though I thought I notice a difference right away but was not sure. I played on it for about a 1/2 hour and came to the conlcusion that it was breaking up sooner.

Any thoughts?

Joe