JVM crackling on resonance control.

Discussion in 'Marshall Amps' started by stickyfinger, May 13, 2021.

  1. stickyfinger

    stickyfinger Well-Known Member

    Nov 11, 2010
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    Its isolated to the resonance control and that tube position. Not a tube issue, tried many new ones. The sound is very very faint and you may not even notice it till your head is near the grill cloth. All controls set to zero it is extremely faint.. turn up the resonance and you can hear a slight crackling becoming slightly louder.

    The amp works an plays fine. The crackling is not causing any on stage noise issues because it is very faint. Just curious if this is inherent by design.

    Can you JVM owners try and see if this is normal on your amps?
    SkyMonkey and JM5010 like this.
  2. Whizzercone

    Whizzercone New Member

    Feb 3, 2021
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    Put it on 0 and don't worry about it.
  3. PelliX

    PelliX Well-Known Member

    Jun 16, 2020
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    I haven't actually checked the circuit on a JVM itself, but assuming (!) that it's the same as on most Marshall amps, the Resonance control is a just a capacitor/resistor combination in the power amp stage. Is the crackling at a constant speed? It could be a capacitor somewhere in circuit that is doing this all the time, but the effect only becomes audible when the control is way up.

    Does the crackling cease entirely when Resonance is at 0? Do any other controls incur similar noise?

    You mentioned 'on stage', does it occur at multiple locations (so ruling out it's AC source related)? Also, just to make sure, the amp does this without an input lead attached, right?

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