Spitfire build tone pot distortion

Discussion in 'Amp Central Station' started by Gbert, Jan 27, 2020.

  1. Gbert

    Gbert TDPRI Member

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    I just completed a matchless spitfire build and it sounds ok until I turn up the tone knob and then it has an ugly distortion.

    I’ve changed the tone pot and all the tubes and reflowed all solder joints. Chopstick all over with no change. Ran it through a known good speaker cab.

    I’ve have another spitfire I built with the exact same layout etc and it sounds awesome.
     
  2. dan40

    dan40 Tele-Afflicted

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    Richmond Va
    It may be creating an oscillation as the treble is increased. You mentioned that you had chopsticked. Did you adjust any of the preamp wire dress to see if it helps? Are you using any shielded wire on the grids? Have you tried new preamp tubes in each position? A pic or two would help us offer more suggestions.
     
  3. Gbert

    Gbert TDPRI Member

    Age:
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    I’ve adjusted pre amp with no change. No new preamp tubes but several from stock and other working amps. No shielded wire. Previous build works well with as close as I can make the two layouts. The two outputs trannys are different 1608 and 1608a (different wiring for output impedance).

    I think you’re on the right track with oscillation. I had I loud squeal when I first tested as turned up volume. I rerouted the unused o/p tranny wires away from the input section and that solved it.
    Sorry no pics til I get to my shop. Thanks for your help.
     
  4. Gbert

    Gbert TDPRI Member

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    Huntsville Ontario
    Thank you so much Dan. You were right about oscillation and lead dress. I did a significant relocation of all the o/p tranny wires and the problem is fixed. It’s so great to have experts like you available.
     
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