need help with amp noise (soundclip)

Discussion in 'Amp Tech Center' started by ruger9, Aug 17, 2019.

  1. ruger9

    ruger9 Poster Extraordinaire

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    Soundcloud below.

    Prelude:
    It only happens when the amp is LOUD, like gigging-without-micing loud.
    It has happened with 2 different speakers, one of which is brand new.
    It has happened with 2 sets of power tubes, and 3 sets of preamp tubes.

    I think I have eliminated those, meaning it's something inside. It's the static-y sound you hear on the soundclip. And I couldn't get the amp to do it that day, but it has in the past gone into, for lack of a better word, oscillation... that static-y noise seems to be a precursor to the amp going into full blown "weeeeeeeeeeeee" high-pitched noise, and the only way to stop it is to put the amp on standby for a few seconds.

    It's been with a "Fender Authorized Tech" for 3 weeks.... he said "I can't find anything wrong, and I can't turn the amp up loud enough in this room for it to make that noise". :rolleyes:

    Anyone have any ideas? I need this amp to be reliable- it's my gigging amp (a Supersonic 60, the 2nd generation)



     
  2. Wally

    Wally Telefied Ad Free Member

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    There’s a good possibility that there is a bad connection somewhere. If this is a combo, can you run the amp through a separate speaker cab to eliminate vibrations to the circuit? Same test with a head...separate it from the cab. If the problem disappears, then at least you know that it is vibration-induced. Then the
    Fender tech can go chopsticking to find the problem???
     
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  3. mfguitar

    mfguitar Tele-Holic

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    not to sound stupid but are you sure it is the amp and not guitar, patch cables, cord.....

    Even with new tubes it could be the tube sockets. Will the amp create the noise with nothing plugged in?

    Maybe seek out a new tech. If he can't turn up loud enough to recreate the noise what is the point?
     
  4. ruger9

    ruger9 Poster Extraordinaire

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    Yeah, tried different guitars, different cables. I'm using the effects loop, and I does it with stuff plugged into it, and with nothing plugged into it. I tried to eliminate everything I could before taking it to a tech.

    And I agree on the tech- I'm going to ask him if he's willing to stick around after closing to "turn it up" out on the main floor of the store, and if not, I'll have to pick it up and go elsewhere... unfortunately, I know of only 1 other tech in the area.

    The noise: it only happens when playing (unless it goes into the full oscillation described above), and loud. Palm mutes seem to really set it off, low notes. Whether it's chugging on the low E string, or doing the "Hold The Line" riff as in the soundcloud clip, it's loud palm mutes that really do it.
     
  5. ruger9

    ruger9 Poster Extraordinaire

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    I do have another cab, but the speaker is only rated for 50W. I have no idea how much wattage I'm pushing with the 60W amp when it makes that noise, but I'm concerned I could blow the other speaker... it's a Cannabis Rex, I've had it for years, and don't want to damage it...

    Could a loose connection (or maybe a bad solder joint), cause that noise, and if so, is that capable of going into "full noise"? Meaning, sometimes, when the amp goes into the constant high-pitched squeal, I stop playing. Nothing is vibrating, but the amp is still squealing.
     
  6. Wally

    Wally Telefied Ad Free Member

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    Once that noise begins, it will continue as it is an oscillation. Have you slapped the sides and top of the amp when it is sitting there idling. You may hear the beginning of the noise when you ‘vibrate’ the cab this way. Without a signal being processed, the feedback/oscillation may not occur, but the crackle of a bad connection will be evident. It could be a dirty tube socket, a bad solder connection/joint, a jigggling slip on wire connector......lots of possibilities.
    With the amp at idle, wiggle the tubes in their sockets. Is there any noise created...crackle/pop sort of thing? If so, pull the offending tube and reinsert it...several times...with the amp off. This could cure the problem...maybe not. This is about all one can do for: the outside...other than check the speaker out, Reverb cables, etc.
    are you running the amp at full tilt when this occurs? Unless you are, the Can Rex should hold up long enough to give you some clue. I understand your caution, though. Do any of your band mates have a cab that will stand up to your normal usage.....maybe the bass player. We are not looking for anything other than the elimination of the vibrations in the cab.
     
  7. jvin248

    jvin248 Poster Extraordinaire

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    .

    Only on low notes = vibration problem inside the amp. There is a broken trace on the circuit board/point-to-point posts/or tube sockets.
    Sometimes ceramic power resistors rocking back and forth because they have mass and breaks the solder joints. Sometimes big caps.

    Sometimes if you take the amp out of its case, you can't repeat the problem because it's the resonance of the assembled system that vibrates at the right location of that component. Thus the repair tech can't replicate the problem while it's open where he can look at it.

    "Chop sticking" or "tap test" can uncover issues. If you try it yourself, remember there are 400 volts+ still in parts even when the amp is off or unplugged. Big capacitors that can unleash that energy all at once. Example here, using a dummy load and oscilloscope instead of the speaker though.



    .
     
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  8. ruger9

    ruger9 Poster Extraordinaire

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    Thanks for those last 2 posts guys. Alot of info. When I get the amp back, I'll look into some of this stuff.

    Frankly, I'm not sure I want to deal with PCB amps anymore... especially ones with a bunch of paddle connectors like the Supersonics. I think I need a handwired amp, just so it's easier for me to troubleshoot, and even repair stuff myself. I can solder- but I don't have the experience required to do PCBs.
     
  9. schmee

    schmee Poster Extraordinaire

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    I don't hear it. But don't assume static-y problems are easy to find in a hand wired amp either....
    -Try the different cab test for sure.
    -Does that amp have plastic input jacks? They can be an issue.
    -As mentioned, with it just idling.... chopstik or tap each tube or tube socket area inside. Any static?
    -Wires or solder traces to tube sockets are a big thing for these problems. Cold solder globs especially, that look good but aren't.
     
  10. ruger9

    ruger9 Poster Extraordinaire

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    Really? It's prominent in the first 3 seconds of the cip...
     
  11. schmee

    schmee Poster Extraordinaire

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    I hear feedback there, is that what you mean? I thought this was a static-y sound...?
     
  12. ruger9

    ruger9 Poster Extraordinaire

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    That's NOT feedback. That's some kind of electronic static-y/squeak.

    It's almost like the sound you get when plugging in a guitar, for a split second before the connections are fully made. Or maybe similar to a loose jack in a guitar... you move the cord, that noise happens, but you never really fully lose signal...
     
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