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Help, I have the dreaded harmonic buzz

Discussion in 'Amp Central Station' started by King Fan, Dec 10, 2017.

  1. moosie

    moosie Doctor of Teleocity Silver Supporter

    Age:
    60
    Jul 18, 2010
    Western Connecticut
    OK, move to a new room, pronto! :lol:

    Try standing on one leg, too, while you're at it.
     

  2. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    So while I decide to go sleuthing again -- this will be like my fifth try :( -- maybe another way to narrow the choice between cab and chassis is to eliminate cab, if I can.

    Does anyone have tips on how to isolate and identify cabinet buzz if it is cabinet buzz? I already tried leaning and pushing on all cab surfaces inside and out, and removing the back panels, and tightening (and holding down) all fasteners and hardware...
     

  3. homesick345

    homesick345 Poster Extraordinaire

    Jan 20, 2012
    Beirut, Lebanon
    I have an email from Mark Baier years ago; about buzz in a Victoria 35310 (bandmaster)

    He suggested isolating the chassis with toothpicks

    (inserting toothpicks between chassis & cab)

    I would try it (my victoria buzz was actually power tube related)
     
    King Fan likes this.

  4. Thin69

    Thin69 Friend of Leo's

    Oct 28, 2009
    Galveston, TX
    Have someone else play the guitar at the offending frequencies. Probe around side the cabinet pressing down on everything. Found many problems through the years this way. Do you have a spare speaker cab to try. Voice coil problems are very common.
    Good Luck!
     
    King Fan likes this.

  5. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    Thanks. That's a pretty solid source! I've been trying to think of ways to isolate the chassis from the cab. I'll try it.

    Thanks, T. Good ideas. I'm starting to question everything, so I'm gonna revisit my initial speaker / cab / chassis recombinations....
     

  6. moosie

    moosie Doctor of Teleocity Silver Supporter

    Age:
    60
    Jul 18, 2010
    Western Connecticut
    Did anyone mention using a looper yet, to generate your tones? Saves you from buying the helper a case of beer...
     

  7. milocj

    milocj Friend of Leo's Ad Free Member

    Aug 21, 2005
    Michigan
    I've read through this and don't think I have seen this possibility mentioned yet...Is the speaker basket touching the output transformer? They can get really close with either certain speakers or larger transformer upgrades. I've had to index speakers before, or make sure the the chassis is pulled slightly back when tightening the screws to keep from touching the basket in a replacement speaker.
     
    King Fan likes this.

  8. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    Thanks, milocj. I’ll check, but I don’t think so. I turned the amp up more last night and the buzz did sound more metallic. Hope to get some time today for more testing.
     

  9. philosofriend

    philosofriend Tele-Holic

    568
    Oct 28, 2015
    Kalamazoo
    Tightening the chassis mounts could warp the cab, allowing a cab buzz to happen. I would automate the signal input, then see what I heard when tightening the chassis mount screws. I might try tightening them in different orders, amount of tightness, etc. The screws could also be warping the chassis. If there was any easy way to put some rubber strips or grommets between the chassis and cab I might try that. (If that fixed it I would locktite the screws and call it good.)
    I liked the suggestion to put the thing upside down, try it every which way, shake it...

    Overall, everything you are trying makes perfect sense. Aggravating, ain't it?
     
    King Fan likes this.

  10. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    Thanks. Another great idea. I kinda wondered about that interaction, since the buzz seems to happen with the chassis tightened in place.

    I really appreciate all these new ideas, because as you can guess I've already tightened and tapped and tugged all sorts of the usual suspects.
     

  11. homesick345

    homesick345 Poster Extraordinaire

    Jan 20, 2012
    Beirut, Lebanon
    don't forget to tighten the baffle (if floating) - also chassis shouldn't touch the baffle

    also check the speaker cable end (& input jack) tighten it too - & also if the cable is rubbing onto something

    you even want to check the casters in the bottom & tighten them

    tighten the tube retainers (the clamps) - have them tight on the tube bottom

    the trannies - check them/tighten the screws
     
    King Fan likes this.

  12. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    Two steps forward and only one back! I tried the steps here I hadn’t tried... and behold, isolating the chassis with toothpicks seemed to help. I tried doing that with 3mm window foam strips instead; not so much.

    OTOH I can't feel or hear exactly where the resonance lives in or around the chassis. Still, all this helps me feel more confident the noise involves the chassis. Gotta figure out how to diagnose the inside — as I say it doesn’t happen when I uncounted the chassis, even if I rest it on the cab. I’ve got a few more ideas to try to see if some wire or part or even the board itself resonates.

    In the meantime, the buzz is definitely a lot less with my high-tech toothpicks between the chassis and cab. I’d say almost gone. But I’m going to recheck. Like all really devilish gremlins, this one is variable. ;-/
     
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  13. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Really glad you are closing in on this, @King Fan . I've been watching with interest, hoping to learn from your pain...
     
    King Fan likes this.

  14. dougstrum

    dougstrum Tele-Meister

    384
    Oct 6, 2015
    blu ridge mtn cabin
    One of my my amps is a real shaker! Can't set anything on it
    at gig volume...
    I put foam weather stripping around the chassis where it contacts
    the cabinet, that really killed a lot of the rattle and buzz.
     

  15. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    Good idea -- I may have to try stiffer, wider padding strips, as the 3mm are only about 6-7mm wide, and they really compress down easily. The big ol' magnet in that DT10 does pack some punch -- my vintage-y alnico speakers are all like 'wow, check the new guy.'
     

  16. moosie

    moosie Doctor of Teleocity Silver Supporter

    Age:
    60
    Jul 18, 2010
    Western Connecticut
    I'm picturing a chassis suspended on springs, like a reverb tank... :twisted:
     
    theprofessor likes this.

  17. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    I've been trying to find an old air-hockey table to float it on... :D
     
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  18. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Or the whole thing suspended from the ceiling, like Dick Dale's 6G15!
    QlOh-MciTRezfdFA4t1I8g.jpg
     
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  19. dougstrum

    dougstrum Tele-Meister

    384
    Oct 6, 2015
    blu ridge mtn cabin
    Is that like bungee jumping for amps~
     

  20. trouserpress

    trouserpress Tele-Meister

    300
    May 4, 2015
    Leipzig
    Magnets will hold it in mid-air.

    For 'dividing': Place pieces of (slightly surmounting) foam or sponge everywhere in the chassis where no delicate components will be bent. Then mount the chassis and listen.
     

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