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SE guitar tube amp ... strange noise

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  • SE guitar tube amp ... strange noise

    Hi,
    I've built an SE tube amp, basically on the AX84 High Octane schematic ... anyway, I'm not on the first build, I actually finished quite few, but this one is very strange ...
    Here are the fact: I got a low frequency hum in the speaker, EVEN with primary winding of OT in air! that's right, I tested with the OT connected just to speaker, and the PT started, and his secondaries not connected, and tubes removed too!
    I initially thought that the PT are inducing somehow a current in the secondary of the OT, witch is connected to speaker, so I removed the OT out of the chassis, and put a lot of space between those two transformers, but the noise is still present, and starting right after I switch on the power switch ...
    Is very odd, I have two separate transformers, with no input (for OT) and no load (for PT), and the speaker is humming ...
    I don't know if I made myself clear, english is not my native language , but if someone ever heard such thing, please give me a clue, because I begin to suspect something alien here ...
    Thanks.

    LE. I've read most of the topics since a lot of them are regarding hum of many kinds ... well, I guess none is comparing to mine I mean, hum without the OT tight in the circuit ... that's something else, isn't so?
    More on that behavior: the hum is goes instantly when I switch off, I have an tube rectifier schematic, with russian 6u5c tube, which has separate heater winding, 6.3V too, not 5V. Seems like a problem with that PT, but I don't figure out how he introduce hum in output speaker, without any connection in the amp, all wires just disconnected ...
    Last edited by iulker; 03-30-2010, 06:52 PM.

  • #2
    no suggestion, nobody ... ?

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    • #3
      You got any pics to upload?
      Building a better world (one tube amp at a time)

      "I have never had to invoke a formula to fight oscillation in a guitar amp."- Enzo

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      • #4
        Your speaker is probably too close to the power transformer.
        WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
        REMEMBER: Everybody knows that smokin' ain't allowed in school !

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        • #5
          Originally posted by loudthud View Post
          Your speaker is probably too close to the power transformer.
          no, definitely is not that, I have a 3 meters cable between the amp and the cabinet, for testing purposes ... thanks for your reply
          it's weird still ...
          I'll try to make some pictures, maybe a video, that will probably help much more

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