Bacon frying sound in amp at idle...

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by brewbaker, Apr 20, 2008.

  1. brewbaker

    brewbaker Supporting Member

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    in fact all the tme. My Vibroverb clone it is. Just started hearing it recently but can't remember the likely thing to check--preamp tubes? Any help appreciated.
     
  2. phatster

    phatster Member

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    Have some eggs and toast and all will be good....Seriously...It could be a number of things...my first guess would be rectifier or power tube.
     
  3. Blue Strat

    Blue Strat Member

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    When it starts smelling like bacon, send me your address. :D

    Preamp tubes, plate load resistors, treble cap, coupling caps (in that order) are what I suspect. What EXACTLY is this amp? New amp? Converted old amp? or????

    Do any of the controls affect the volume level of the noise?
     
  4. mcuguitar

    mcuguitar Gold Supporting Member

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    Hi Dave,
    How many hours on the tubes? If you're gigging with this amp...and it's been over a year, year and a half...change the power tubes and rectifier tube first. Peace, Jon.
     
  5. brad347

    brad347 Member

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    1) that depends on the tubes
    2) I would never replace a rectifier tube unless it was failing. It will almost never cause that type of crackling because it is not directly in the audio path and is not directly connected to the output of the amp.
     
  6. Monroe

    Monroe Guest

    Failing plate load resisters on the preamp tubes can cause the "frying eggs" sound. Did you use carbon comps?
     
  7. brewbaker

    brewbaker Supporting Member

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    The amp is a Bandmaster Reverb converted to blackface specs--Vibroclone schematic. The plate resistors are new carbon comps as are all the components in both tone stacks as well all the caps. The tubes have low hours--JJs all.

    The sound doesn't start right away. It creeps in after the amp has been on awhile.
     
  8. Blue Strat

    Blue Strat Member

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    Same advice as in my first post. Preamp tubes, plate load resistors, etc.

    See if any controls affect the noise level.

    For starters, clean all the sockets with contact cleaner.
     
  9. brad347

    brad347 Member

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    I'd wager plate load resistors if tube and tube socket stuff doesn't clear it up.
     
  10. AndyG

    AndyG Member

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    I had this same problem tried everything. Saw this post last night and blue strat mentioned one thing I didn't try. It was a bad treble cap, I never would have thunk it. Blue strat you the man.

    Andy
     
  11. brewbaker

    brewbaker Supporting Member

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    Thanks everyone. I'll try things one by one till I get it.
     
  12. Blue Strat

    Blue Strat Member

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    You still haven't told us which, if any, controls affect the hiss. This could help narrow things down.
     
  13. Blue Strat

    Blue Strat Member

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    Yep, this is one of the less likely ones but I've seen it a few times.

    Another one was the 3.3Meg resistor between V2 and V4. I had a noisy one once. The noise persisted no matter where the controls were set because this is after the volume controls and tone stacks.

    I replaced it and still had noise. Found out, after hours of denial, that the one I replaced it with was noisy too! What are the odds?
     
    sjwieczorkow likes this.
  14. brewbaker

    brewbaker Supporting Member

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    The controls don't have any effect. They can all be down and the noise persists.
     
  15. Blue Strat

    Blue Strat Member

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    See if removing V1 or V2 stops the noise and report back.
     
  16. alltone

    alltone Member

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    Try pulling pre amp tubes ,one at at time starting at the inputs. If it's still there when you're down to the Phase inverter..........as mentioned..Tube..plate load resistors.. output tubes? Not much left after that??
     
  17. alltone

    alltone Member

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    Right..:AOK..dial -up connection got me in last, again!!:D
     

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