High pitch sound coming from amp..ugh!

Discussion in 'Amps and Cabs' started by GregWV, Feb 25, 2012.

  1. GregWV

    GregWV Member

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    I've got a new VoxAC15HW1 and when I play certain chords I get a high pitched note that sounds like a spring rattling.

    Microphonic tube?

    Or, is it just the speaker making the tubes rattle?
     
  2. rgee27

    rgee27 Supporting Member

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    Microphonic tube for sure... tap each tube with a pencil to see which one is making the noise.
     
  3. GregWV

    GregWV Member

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    Tap with pencil While it is on? What will it sound like?

    Power tube or pre amp tube?

    Could it be rectifier?

    Thanks- I have gig in morning.
     
  4. lang.murphy

    lang.murphy Member

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    Well... I can't say for sure what the root cause is for that high pitched note that sounds like a spring rattling. Yeah, might be a microphonic tube...

    So... anyway... usually the first step in TS'ing a tube amp is to swap in different "known good" tubes. Lacking a spare tube inventory, I guess the next best thing would be to swap tubes from one location to another. A microphonic tube in V1 might not have the same effect in Vx... x being anything other than 1. ;-)
     
  5. tnt365

    tnt365 Supporting Member

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    yes tap the tubes while it is on and the guitar volume is up. If it rings or makes a noise then it may be microphonic. Tubes are kinda cheap, so go buy a few preamp tubes before your gig (most likely the problem, cross your fingers) and replace the ones you have. If it fixes the problem (which over %50 over the time it will) then you are lucky. If not, you want a tech to look at it if you are inept. That is a nice amp, so putting a little love into it is gonna be worth it. Cheers!
     

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