What makes the 'frying bacon' sound...

Discussion in 'Amp Central Station' started by King Fan, May 22, 2019.

  1. King Fan

    King Fan Friend of Leo's Ad Free Member

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    Funny how you start to hear your amps better over time. I've come to realize my VibroChamp has a low, constant sizzle *as soon as you turn it on* (it sounds like it's in the switch, it starts so fast).

    I know this is probably suggestive of a known issue. Which issue: where to look, how to fix?

    FWIW the pots are original. I replaced the cap can and other e-caps. I kept the single-strand heater wiring. Just because the slide switch felt so 'loose' I did replace it with an NOS, but of course the noise didn't change.

    Suspects? I'm running all carbon comp resistors except for the 6V6 cathode. This includes the dropping resistors (2w) and V1 plate load resistors (1w). Most are NOS Allan-Bradleys, one is some other brand, and only a couple were original to the amp (they tested good though.)

    The amp works and sounds great otherwise. And let me repeat: The sizzle starts the second you switch on. That's gotta be a clue, right?

    IMG_5001.jpg
     
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  2. galaxiex

    galaxiex Tele-Holic Silver Supporter

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    Is it a sizzle or a crackle? both?

    Cold solder joint somewhere?

    I would start looking at anything high voltage..

    Check tube pin tension too.
     
  3. schmee

    schmee Poster Extraordinaire

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    I normally relate "sizzle'" to when a note is played. This sounds like it's doing it when just on and not played right?
    Is it hissing? Like a TV turned up high volume not on a channel?
    Not a pop/crackle right?
     
  4. Snfoilhat

    Snfoilhat Tele-Afflicted

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    Does it behave the same with the tubes removed? I am familiar with people talking about resistor noises, but I don't really know if they are they inserted into the signal like other amp self-noise and reproduced at the speaker, or are they mechanical like a transformer vibrating, or both? Sorry I'm no help but you've got me curious!
     
  5. mherrcat

    mherrcat Tele-Holic

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    Pre-amp plate load resistors?
     
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  6. King Fan

    King Fan Friend of Leo's Ad Free Member

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    LOL, you guys helped more than you thought. Since descriptions are hard, I went down to record the sound and found out a) it only does it when cold and b) only when first turned on -- it fades out as the amp's slight hum comes up on warmup. I swear it used to persist, but maybe it is just so obvious with a cold, silent amp... or maybe it is getting better.

    Let me ask the question more generally. What makes the frying bacon noise you hear discussed in amp forums? I've read startup procedures that say, "listen for howl, hum, buzzes, bacon frying, etc." And there was a thread on here very recently -- can't find now -- that suggested frying bacon comes from plate resistors (if I understood).

    To be specific, it is *not* regular hiss or hum. It is not associated with a note. It isn't sizzle in the sense of note dynamics or overtones. It's not a pop or crackle; well, it's like a constant, minimally varying sound of micro bubbles in fat. It's like bacon in the pan on nice low heat after a layer of liquid bacon fat forms.

    So, less urgent, I think my case of it is on the mend, but a more general question. Does it have a typical cause or set of causes?
     
  7. schmee

    schmee Poster Extraordinaire

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    The Bacon Frying thing is one of the most elusive to find for me. I have had it on a Super Champ XD. Just as the note fades when playing. Kinda like a garble sound. I also had an Emi Texas Heat that seemed to do it to a lesser extent in the same way as the note fades out. I wonder if that's saying something.. connections?
    I think on some amps it's the nature of the design. I had an EL84 powered cheap amp that just seemed to have that tone when pushed at all. But on amps that normally don't do that, it's tough. Pre tube sometimes maybe.
    I know old plate resistors often create hissing. Not sure about the Bacon fry though.
    Here's an old thread with an example of Bacon Fry that fits what my head says it is:
    http://www.tdpri.com/threads/old-jensen-p12r-rattle.887910/
     
    Last edited: May 22, 2019
  8. Snfoilhat

    Snfoilhat Tele-Afflicted

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    Is this some really niche influencer marketing for the bacon industry, @King Fan? Suddenly hungry:eek:
     
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  9. dogmeat

    dogmeat Tele-Afflicted

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    mmmmmmmmmmmmmm..................... baaaacon
     
  10. 1300 E Valencia

    1300 E Valencia Friend of Leo's

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    THAT is the dreaded "voice coil rub". It means the speaker is on the way out. That said, 99% of noise in a tube amp is ... a tube!
     
  11. theprofessor

    theprofessor Friend of Leo's

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    Hardly an expert, but based on when you say it happens, I'd say it's the rectifier tube.
     
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  12. King Fan

    King Fan Friend of Leo's Ad Free Member

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    Rectifier tube... current inrush... The Force is strong with this one!!

    Excellent idea, Professor. Thanks


    Sent from my iPad using Tapatalk
     
  13. muscmp

    muscmp Tele-Afflicted

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    have you chopsticked every connection? swapped out preamp tubes? checked voltages? pulled out tubes a few times and reinserted?

    that's all i can think of presently.

    play music!
     
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  14. 66tele

    66tele TDPRI Member

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    The "frying bacon" noise is often associated with carbon composition resistors. The composition is porous and absorbs moisture from the air and then releases the moisture when the amp is running, creating the "frying bacon" sound. The plate load resistors are the usual culprit. Try replacing them with 1 watt metal oxide resistors.
     
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  15. King Fan

    King Fan Friend of Leo's Ad Free Member

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    Aha, thanks, that explains why I read it might be plate resistors. I wonder... that may not be the bacon I’m looking for here, since I use 1/2w CCs on the plates in most of my amps (blame Mr. Keen) and this is the only one that does it — and it has 1w there. Plus (I may be wrong) I wouldn’t have thought that noise would appear instantly on power-up. And now mine actually disappears after warmup...

    I guess I’m asking about a sound associated with a *fault* that we look for on startup or in troubleshooting, not a conventional (if slightly noisy) component. I’m also thinking I may be asking one of those infamous “I don’t know what I’m thinking of — do you?” questions.
     
  16. King Fan

    King Fan Friend of Leo's Ad Free Member

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    Good thoughts.. I did most of that and more during an extensive rebuild of this amp, and couldn’t reduce the bacon noise then. But since the noise appears 0 sec after I flip the switch, I’ll check the power and heater sections again. And good idea on sockets — 50-year-old sockets are always a suspect.


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  17. Digital Larry

    Digital Larry Tele-Afflicted

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    I'm thinking of wrapping my rectifier tube with bacon... best of both worlds there...
     
  18. galaxiex

    galaxiex Tele-Holic Silver Supporter

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    Well.....

    We have guitars that smell like cake...

    Why not amps that smell like bacon? :D
     
  19. soundchaser59

    soundchaser59 Tele-Holic

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    These are all the things that have caused this in my amps.....

    scorched plate resistor
    bad or cracked solder joints
    hairline crack in a pcb
    bad tubes, esp power tubes or phase inverter
    dirty tone pots
    bad esp old caps

    This noise in my amps has never been caused or fixed by tube pin sockets or sleeves. The last one that did this was serviced by the guy who actually built the amp at the factory. He said it seemed to him like it had been dropped, which I felt was very likely.
     
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  20. 1300 E Valencia

    1300 E Valencia Friend of Leo's

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    If it's a tube map, it's a tube, unless proven otherwise.
    Remember, one-at-a-time, then test. Rinse and repeat.
     
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