VoxAC10 hum/buzz. Why?

Discussion in 'Fred's Barcalounge' started by Jelly Roll Horton, May 3, 2021 at 12:13 AM.

  1. Jelly Roll Horton

    Jelly Roll Horton Country Gent

    Nov 10, 2017
    Portland, OR
    My Vox AC10 has a mild buzz or hum ( hard to describe) when I engage the gain knob to activate the reverb while playing my Gretsches. If I place my fingers on the strings, or if I turn the gain knob back to zero, this stops.
    It is also occurs when I play my Tele, but placing my fingers on the strings in this case has no effect.
    I replaced the power tubes last year thinking this might be the prob, but no happiness. Amp is 3 years old.
    My practice space does not have flourescent lighting, so that isn’t the cause.
    But what might it be? :confused: And what to do?
     
  2. TubeLife

    TubeLife Gretschie

    Age:
    45
    486
    Jan 23, 2020
    Chicagoland
    My LED dimmers create havoc on my amps and buzzing and the dimmers are on the next floor up. When I play I turn the culprit dimmer off and all is well. Usually when the buzzing stops while putting your fingers on the strings or bridge means your guitar is properly grounded.

    Just have to play the chasing game and figure out what’s causing it. Plug the amp in other rooms or somewhere else entirely if possible. Or it could be the amp, cables etc.....hard to tell without hearing it.
     
  3. wabash slim

    wabash slim Gretschified

    Age:
    71
    Feb 10, 2010
    lafayette in
    What else is on the circuit or on the same phase?
     
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  4. Jelly Roll Horton

    Jelly Roll Horton Country Gent

    Nov 10, 2017
    Portland, OR
    Two computers, two amps, two printers, and one scanner are all on the circuit. During practice time, only one of the amps and one of the computers are off; everything else is on. One computer, one printer and the scanner are all on a table above the amps.
     
  5. wabash slim

    wabash slim Gretschified

    Age:
    71
    Feb 10, 2010
    lafayette in
    That stack of electronics could be your source of interference. Also, if the buzz stops when you touvh the strings, it's a ground issue within the guitar. Might be a bad cable as well. I know people that had problems due to their neighbor's electronics, and by high tension lines nearby. Dimmers, LED, neon, and fluorescent lights, fans, HVAC can all be problematic. We had a fish tank heater when I was a kid that was a major annoyance. Turn your amp 90 degrees, try a different room or wall. Make sure that your AC cables do not run alongside signal wires.

    Spurious Emissions (great band name, by the way) can be a nightmare to track down.
     
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  6. Jelly Roll Horton

    Jelly Roll Horton Country Gent

    Nov 10, 2017
    Portland, OR
    Thanks Slim. I ran through all those options, even took the amp out to the detached garage. Still a strong fuzzy buzz when I engage the gain knob, even with no guitar plugged in.
     
  7. TSims1

    TSims1 Gretschified

    Jun 18, 2013
    Atlanta

    One of the tubes?
     
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  8. wabash slim

    wabash slim Gretschified

    Age:
    71
    Feb 10, 2010
    lafayette in
    Could be in the amp then, Take it to a tech.
     
    hcsterg likes this.
  9. Jelly Roll Horton

    Jelly Roll Horton Country Gent

    Nov 10, 2017
    Portland, OR
    Could be. But it’s only 3 years old and has had very light usage. I guess I’ll find a tech, as Slim suggests.
     
  10. Henry

    Henry I Bleed Orange

    Apr 9, 2014
    Petaluma
    Neverending, see that the hum is there even with no guitar plugged in. However, it could be ambient electricity pollution, which you ground when touching the Gretsch - I don't understand why that doesn't happen with the tele.
     
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  11. Jelly Roll Horton

    Jelly Roll Horton Country Gent

    Nov 10, 2017
    Portland, OR
    Me either. Nor do I understand why a $450 amp has this issue after only three years. :mad:
     
  12. TW4990

    TW4990 Gretschie

    245
    Aug 20, 2016
    Sydney Australia
    Have you tried spraying contact cleaner / lube into the pots?
    Could be a dry joint somewhere in the circuit.
     
  13. hcsterg

    hcsterg Friend of Fred

    Feb 13, 2012
    France
    This kind of issue is sometimes a pain to eradicate... ;)
    You speak about hum with reverb : when you zero the reverb pot, does it ceases ? o_O

    A+!
     
  14. stevo

    stevo Friend of Fred

    May 1, 2012
    Atlanta
    Is it this guy?

    https://voxamps.com/product/ac10-custom/

    I've been watching those and have shied away because of so many descriptions of hum/buzz. Unfortunately for you, I'm reading descriptions of them started out new with buzz.

    From your description - you're turning the gain knob to activate reverb? I'm unclear.
     
  15. Archtops

    Archtops Gretschie

    377
    Mar 4, 2021
    SoCal
    Sounds like a grounding issue. Maybe check to see if the input jack is fully operational and not grounding out.
    Just a guess at this point. Good luck!
     
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  16. Jelly Roll Horton

    Jelly Roll Horton Country Gent

    Nov 10, 2017
    Portland, OR
    Yeah. That’s what it takes. And that’s my amp.
     
  17. Tony65x55

    Tony65x55 Gretschified

    Age:
    64
    Sep 23, 2011
    The 'Shwa, Ontario, Canada
    Jelly Roll, I am guessing tubes. Vox ships these amps with the cheapest Chinese tubes they can find. I like Tung-Sols in the preamp and JJ's in the power section. Maybe you have a buddy you can borrow these from to test them out. Either way, at least it's only four tubes.
     
  18. stevo

    stevo Friend of Fred

    May 1, 2012
    Atlanta
    That's the confusion - why do you have to turn the gain knob to activate the reverb? If that's how it works, I'm surprised. Reverb knob should be all you need for reverb.
     
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  19. Jelly Roll Horton

    Jelly Roll Horton Country Gent

    Nov 10, 2017
    Portland, OR
    I put JJs in last year. May have to try the Tung-sols.
     
    Tony65x55 likes this.
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