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Help with an Ampeg B3-158

Discussion in 'Amps and Cabs [BG]' started by Mario Munoz, Feb 4, 2019.

  1. Mario Munoz

    Mario Munoz

    Jan 6, 2019
    I recently purchased an Ampeg B3, the one with a 15" speaker and an 8" one.
    I tought it was a good deal however when I first tested it, I noticed how the amp produced some kind of buzz whenever I played high notes, anything on the G string would cause a buzz.

    Aparently the buzz is coming from the 8" speaker. I tried both speakers individually and only one produced "the buzz".

    However I wasn't certain that the speaker or the amp were blown. I tried connecting the 8" to an external 30W amp (Rogue RB30) and it made no apparent buzz. Then I hooked up the output from the Ampeg to an external speaker, and it made no buzz either.

    I then made a sound probe so I could check the output from the Ampeg with my headphones, and I heard somewhat of a buzz/distortion, but I'm not sure if that was my probe clipping lowering the gain got rid of the buzz, this doesn't happen using the amp in normal condition, lowering the gain or the volume doesn't get rid of the buzz.

    I've tried some signal tracing using the schematic but had no luck finding the source of the buzz. I've even swapped 'a lot' of the op amps in the amp(this has had solved other issues the amp had)

    Is there anything else that I can try? I don't want to get another speaker as I'm not sure that will solve the issue.

    Could it be a potentiometer? a power transistor? an air leak making the speaker sound like this?
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