Distorted, scratchy vocals from tube amp

Discussion in 'Audio Hardware' started by boyhitscar, Sep 14, 2020 at 10:28 PM.

  1. boyhitscar

    boyhitscar Well-Known Member Thread Starter

    Location:
    NYC
    i recently picked up a used Jolida Fusion 3502 S and i’m noticing scratchy/distorted sound especially on vocals (yes sibilance included but all vocals sound like the person speaking/singing has a congested throat).

    i’ve isolated this to the amp by trying different turntables, different carts, different phono stages, switching to digital, and even using different interconnects.

    the auto-bias indicators for each tube seem fine (light up solid red), but would this be a sign my tubes need replacing? or is there something else i can check/test?

    many thanks
     
  2. Uglyversal

    Uglyversal Forum Resident

    Location:
    Sydney
    I'll bump it for you in case someone knows. I don't have much experience with valves but I thought generally the sound starts to vanish, get very dull or noisy when valves need replacing, distortion might be another problem.
     
  3. Twodawgzz

    Twodawgzz But why do you ask such questions...

    Could be a wire coming loose in the amp's chassis somewhere. If so, a simple resolder would likely fix the problem.
     
  4. vinylkid58

    vinylkid58 Forum Resident

    Location:
    Victoria, B.C.
    Try the easy stuff first. Pull the output tubes and clean the pins and sockets, and clean the connectors on the back as well. If the volume pot is scratchy, try and get some Deoxit into it as well. Hopefully, the auto-bias is working correctly.

    jeff
     
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  5. boyhitscar

    boyhitscar Well-Known Member Thread Starter

    Location:
    NYC
    any advice on how to clean those pins?
     
  6. action pact

    action pact Music Omnivore

    Contact cleaner and a Q-Tip.
     
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  7. Tullman

    Tullman Senior Member

    Location:
    Boston MA
    How many hours are on those tubes?? Most likely too many. I would replace the tubes from a good dealer like Jim McShane, who tests the tubes he sells, so you should have good tubes to install. Cleaning is fine, but it ain't gonna do nothin' for bad tubes.
     
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  8. Wayne Nielson

    Wayne Nielson Forum Resident

    No. There is problem you have not discovered.
     
  9. Tullman

    Tullman Senior Member

    Location:
    Boston MA
    You could just move the tubes in and out which would clear up some oxidation. Still, don't be cheap and replace the tubes.
     
  10. Tullman

    Tullman Senior Member

    Location:
    Boston MA
    You could be right but replacing the tubes is the first step. Any repair technician will tell him the same thing.
     
  11. boyhitscar

    boyhitscar Well-Known Member Thread Starter

    Location:
    NYC
    found out yesterday the tubes have 4-500 hours on them. power tubes are electro harmonix EL34s, pres are tung sol 12AX7s.

    i suppose next month i'll swap out all 8 tubes and report back. and i'll check out Jim McShane, thanks for the referral.

    but assuming the new tubes act the same... any advice on what to do then?
     
  12. Tullman

    Tullman Senior Member

    Location:
    Boston MA
    If the tubes are not the problem then you should contact the manufacturer and inquire about service.
     
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