#1
i bought a marshall dsl 401 and it has 4 12ax7 and 4 EL84

the power amp tubes are new but im not sure about preamp tubes.

so today i played the amp and i noticed that one of my preamp tubes was not orange, but other tubes were glowing orange.
does it mean that i have to change the tube??
#3
are you sure that its not glowing just dimmer than the others? The preamp tubes for reverb, the effects loop and/or phase inverter sometimes don't glow as bright (at least they didn't on my old B-52 amp I had).
#4
^ i dont know and im not quite sure, but it looks like its not glowing as bright as other tubes.
i think one tube is in a cover(you cant see it glowing) and other tubes are without that cover.
but how can i tell that the amps preamp tubes are dying or dead?
Last edited by scream92 at Dec 7, 2009,
#5
Quote by scream92
^ i dont know and im not quite sure, but it looks like its not glowing as bright as other tubes.
i think one tube is in a cover(you cant see it glowing) and other tubes are without that cover.
but how can i tell that the amps preamp tubes are dying or dead?



does the amp sound bad?
#6
i dont know. i bought it used so i dont know how it sounded with new preamp tubes.
i just bought it, like 2 days ago and i think it is more muddy now, but im not sure.

and today when i played it, the amp had some weird sounds not loud but there was some very little noise, i thought it was the speaker but maybe it was the tube.
#7
well, preamp tubes are usually pretty cheap. and if the amp hasn't been retubed it might be a good idea just to retube it...or at least try to replace the suspect one and see if your sound improves.
#8
Some preamp tubes glow brighter than others, some are extremely dim, like the Sovtek LPS. How brightly they glow has nothing to do with proper or improper operation.

If a preamp tube is bad, or going bad, you will hear it in your tone in the form of squealing, whistling or buzzing. AKA microphonics.

If a preamp dies or is dead, you amp will not operate properly. Usually you will recieve no sound from the preamp, as their is an interruption, or void in the signal path.
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