I have had this problem with my Marshall JCM 2000 for a while. It happens intermittently so it has been ongoing.
The issue only happens when playing the amp at high volumes for a long time, so I did not notice the case playing at home. The amp will start to sound like a speaker is blown. This only affects frequencies below 440 hz. If I hit an A chord, the amp sounds great anything below that gives the blown speaker sound.
I took the cab apart and tested all of the speakers. I also glued a loose support I thought could contribute to cab noise. The cab sounds great with my JC120 and my Carvin. No issues with the cab or speakers.
I am going to drag the amp home today from the practice studio to check it out. My initial thought is a tube has gone microphonic or bias drift. There is a set of Mullards in the amp right now that have been in there for around 7 years that get worked hard.
I am going to check the tubes and bias and might throw in a set of GTs I have sitting around. Is there anything else I should check out? Has anyone else run into this problem?
The issue only happens when playing the amp at high volumes for a long time, so I did not notice the case playing at home. The amp will start to sound like a speaker is blown. This only affects frequencies below 440 hz. If I hit an A chord, the amp sounds great anything below that gives the blown speaker sound.
I took the cab apart and tested all of the speakers. I also glued a loose support I thought could contribute to cab noise. The cab sounds great with my JC120 and my Carvin. No issues with the cab or speakers.
I am going to drag the amp home today from the practice studio to check it out. My initial thought is a tube has gone microphonic or bias drift. There is a set of Mullards in the amp right now that have been in there for around 7 years that get worked hard.
I am going to check the tubes and bias and might throw in a set of GTs I have sitting around. Is there anything else I should check out? Has anyone else run into this problem?
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