The other day I was playing my ipod through my 5150 combo (I got new speakers and needed to burn them in) using the rhythm channel. Both the post- and the pre- were on 2 and on the second song into it I heard a distinct "thump" and immediately noticed that I had lost a fair amount of my bass response. In addition I noticed a fuzz and crackle in the speakers (although there is a possibility that this was there all along) Is this a tube problem? and amp problem? a speaker problem? I've just installed new tubes (JJ tubes) within the past 2 weeks and have run the amp neither long nor high at all since installing them. I would love to hear from someone with any sort of experience with this kind of situation, or someone just knowledgeable about tube amps.
AFAIK, you're not supposed to play music from an MP3 through guitar speakers to break them in beacuse the speakers are not meant to handle a full spectrum of frequencies like a PA speaker or a HiFi spearker. i could be wrong, though.
How high was the volume when you were playing the iPod?