When I switched the amp on this morning I noticed that the clean channel distorts constantly, even with my pickups turned down less than halfway (this should be perfectly clean at the volume the amp is set to). What's more, the distortion seems to remain about constant regardless of where I set my pickup output. Normally it would break up slightly for a nice bluesy sound with the pickups at full volume as the Blackouts on my guitar will overdrive the amp by themselves, but now it is even more distorted and unable to be removed.

Is this a sign of a bad tube, or something else entirely? I read everything I could, but that specific symptom doesn't seem to appear under any category of problem. I'm new to tube amps having just bought this on ebay a couple months ago.

Anyone with experience with something like this please let me know!


Also, if I need to replace tubes on this fixed bias amp (Marshall DSL401), do I really need to take it in to be biased (I have no idea how) when swapping for the same tubes? Is changing the tubes themselves as easy as pulling the old one and slapping the new one in its place aside from biasing? Thanks!
Last edited by AJDrac at Aug 11, 2009,
are blackouts actives? cos maybe you could check the batteries on them?

as for the biasing, normally if you buy a matched set of tubes they dont need to be biased i think, but dont quote me on that, im not sure
Thanks for that. I never thought to plug something else in and try it, and with the microphone I had lying around it seems perfectly clear (though of course turned up quite a bit to hear it), so I'm off to find a 9V. Problem solved.