Wheezy, whooshy noises when instrument cable first plugged in?

Discussion in 'Amps & Cabs' started by BenTobith, Aug 31, 2020.

  1. BenTobith

    BenTobith Member

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    I have a strange situation where I hear a constant background noise whenever I first power up my amp and take it out of Standby mode. The noise is a combination of a faint, high pitched squeal and a swirling, whooshing sound, like white noise and radio static with some movement to them.

    However, if I briefly unplug the instrument cable to the amp's input and plug it back in, the noise stops and doesn’t come back ... until the next time I power things up from cold.

    Basically, the noises show up whenever I first power up the amp from cold, and either:
    • With the instrument cable already plugged in when the amp is first powered on.
    • With the instrument cable plugged in after the amp has warmed up.
    In both cases above, this is before I flip it from Standby to On.

    To clarify further, moving backwards from the amp input jack to the guitar:
    • The instrument cable from the amp is plugged into a passive TRS passthrough module on my Emerson pedal board.
    • It is then connected to a series of pedals, all powered by Strymon Zuma power supplies.
    • The Zuma power supplies are plugged in to an Emerson power module, which has an IEC cable to my voltage regulator/power conditioner and wall outlet.
    • From the tuner input is an instrument cable connected to my guitar of choice.
    The two instrument cables, from the amp to pedalboard, and pedalboard to guitar, are 10' Runway Audio cables.

    It is nice that there’s a simple workaround, but I’m curious if anyone has an idea what the root cause might be, or if it signifies anything serious in need of addressing?
     
  2. donepearce

    donepearce Well-Known Member

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    How old is the amp? This is a symptom of either capacitors or valves getting antsy. Valve sockets can oxidise when they stand still. A few vibrations from the speaker will clean them up temporarily, then the noise comes back after they have been stood idle for a while. A bit of prodding around the valves with a long PLASTIC rod can identify a bad contact. But there are lethal voltages (500V) in there, so if you are not completely certain what you are doing, leave it alone.
     
  3. BenTobith

    BenTobith Member

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    Only a month or two old, it's a new Mesa Boogie.

    If it's one of those things, why or how does unplugging and replugging in the cable make a difference?
     
  4. donepearce

    donepearce Well-Known Member

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    Just the physical jolt can do it. But if it is new you can discount components going bad. Another possibility is dirty contacts in the jack. Also try moving the pots around to see if they affect the noise.
     
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  5. BenTobith

    BenTobith Member

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    Is Deoxit safe for an amp input? I have some of that handy.
     
  6. donepearce

    donepearce Well-Known Member

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    Perfectly.
     
  7. Stark Naked

    Stark Naked Active Member

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    When i have that kind of noise, i reach in the back and push the tubes back up in their sockets and that stops it.
     
  8. DrBGood

    DrBGood Well-Known Member

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    I guess nobody asked, but did you try wih the guitar plugged directly into the amp, everything else disconnected ? Same but with different cable ? Same but with different guitar ?

    In another thread, someone was having sustain problems with his brand new guitar, notes would die right away. After a few exchanges, he forgot to tell us that somehow on his processor the noise gate had gotten turned on and was making the notes cut out quickly.
     
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