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RIP Amp help

Discussion in 'Amps and Cabs [BG]' started by atlas_mike, Feb 26, 2013.


  1. atlas_mike

    atlas_mike

    Feb 26, 2013
    Hey guys, I've been lurking for a while, but recently had a fairly serious instance during a gig: after an extremely loud show, my amp smelled of smoke/melting and it ceased to make a sound above a distorted whisper. Not rattling, just... very quiet and distorted, even with my effects turned off.

    A little background: I play a P-Bass, through a short effects chain of a tuner, a distortion, a fuzz, a booster, and a looper. This all goes into a Peavey Tour 450 head, which is connected to an Ashdown 410 (RMS power rating of 450). I play... aggressively. A lot of fuzz, chords, forced feedback, etc. Not metal, just angry.

    A few nights ago, I had to turn up my head a lot more than I thought I would have to and the amp did not respond well (some rattling, a more distorted clean tone than I would've liked). The following night, another gig that ended with the amp losing steam until there was nothing left. I might have had the pedals turned up above unity gain. I mean, probably did. Yeah, I totally did.

    My question: What failed? the head or the cab? I smelled smoke from the cab, but the head could be busted, too, for all I know. I've already made plans to check out some new amplifiers, but I don't want to make the same mistake again. Don't tell me to play different, because this is my art, etc etc.

    TLDR: Blew up my amp, how do I not blow up amps anymore?

    Thanks, for your help.
     
  2. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    How did you go from the Peavey to the Ashdown. I hope this isn't insulting, but I just want to make sure you didn't connect the speaker output of one to the bass input of the other.

    Next, go with what's easy first, which is to pull one of the drivers from the cab and take a look inside with a bright flashlight.
     
  3. atlas_mike

    atlas_mike

    Feb 26, 2013
    Oh, definitely not; it was all hooked up right. I mean, as I said, the thing worked well enough for almost the whole show until the very end. I'm excited to pull apart the cab and get into the guts of it. I guess I probably just overdrove it?

    I guess the question I have is: if the cab is 4ohms, and the amp is looking for a 4ohm impedance, does blowing the cab also blow the amp because now there's no impedance on the other end?
     
  4. IPYF

    IPYF

    Mar 31, 2011
    It sound like a monstrous amount of modified input signal to be tossing at that amp.

    A jack spike or an overpeaked string strike could have melted the input cap in your head. When my input cap went all I could hear was a dull low volume distortion, right before the amp said "Fk this noise!" and went goodnight.
     
  5. 254 stringer

    254 stringer Supporting Member

    Apr 15, 2010
    Waco Texas
    How to avoid blowing up amps, get something bigger than you need so you can turn it down instead of maxing out a smaller rig.
     
  6. atlas_mike

    atlas_mike

    Feb 26, 2013
    Okay, so I'll take apart the cab and check out the drivers and then I'll take apart the head and check out the caps. If the input capacitor is done, can I just replace that? Or is it a more serious problem?

    And stringer: yeahh, being on a budget made it seem like such a good idea to get the cheapest stuff. Dumb. Always plan ahead.
     
  7. IPYF

    IPYF

    Mar 31, 2011
    Input cap is not a big deal. Cost me less than not much.

    Do you run your FX through a loop or in through the input?
     
  8. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Does the cab have a tweeter? If so, then the tweeter or crossover could be what you smoked. Beyond that, capacitors are an unlikely root cause of your problem.
     
  9. Jazzdogg

    Jazzdogg Less barking, more wagging!

    Jul 29, 2006
    San Diego, CA
    To determine whether the problem is with the head or the cab, try the cab with a different head. While you're at it, swap out the cables with ones you know are good.

    Do you already know how to check the individual loudspeakers in your cab with a 9V battery?
     
  10. atlas_mike

    atlas_mike

    Feb 26, 2013
    Okay:

    All of my effects are in through the input.

    The cab does have a tweeter, but I wasn't getting hardly any sound at all through the thing, so I don't think that's the problem. I mean, I'm sure the tweeter went, but I just think it's more than that. I guess it could be the crossover, then?

    I do know how to check individual speakers with the 9V! I saw the video while I was researching my problem!
     
  11. You have not mentioned the impedance of the speaker cabinet. 4 or 8 ohms? Are you using a proper speaker cable and NOT a guitar cable? If you smelled smoke from the cabinet, I would suspect you have fried the voice coils in your speakers. By using distortion, fuzz.... you are creating distortion which to the speaker appears more like DC voltage instead of the AC voltage sinusoids it is expecting to see. If you were to see your signal on an oscilloscope, you could visually see what I am saying. The voice coils can only take so much DC voltage and then they overheat and fry. I would suspect if you plug your amp head into another cabinet, it will be fine.
     
  12. OMG, distortion can fry tweeters but not woofers. If your amp is putting out DC it's broken.
     
  13. You may have fried the input gain device (opamp or FET transistors). Try plugging into the effects return with your bass only, if it sound okay just not as loud the power amp is okay and you damaged the preamp.

    How do you avoid it, depending on the design the input pad or active input may help.
     
  14. Do the battery test on the cabinet before you do anything else. If you hear no thumps then most likely you have toasted the drivers. If the cabinet has series/parallel wiring, you possibly may have a couple of workable drivers left. Now is the time to pull the drivers one at a time and do the battery test on each one. You don't have to remove the wiring, just ensure that the cone moves on the driver you are testing.
     
  15. atlas_mike

    atlas_mike

    Feb 26, 2013
    Okay, update time:

    My head works perfectly fine, it's just the cabinet that doesn't work. I've already gotten a new cabinet, so at this point, this is just a project for me.

    I tried the battery test and all I heard were clicks, no thumps and no movement. Is the only cure new speakers?
     
  16. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    When stuff starts sounding wrong, get it fixed. Don't keep using it until it blows up. Repairs are much cheaper that way. Plus once its repaired, trade it in for a more suitable amp.
     
  17. This equates to new speakers needed or re-cone time if kits are available.
     
  18. Bassmec

    Bassmec

    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    No man you are treading on this guys performance originality:D
    Just before the voice coils blistered so much it began to weld the coil assemblies to the magnet front plates,there was this tone! man:D
    It sounded exactly like a buildings falling down continuously with the odd clump and clang of scaffold poles bouncing off concrete. Then there was that acrid magic smoke drifting all over the the stage with the fading bass sound until all that was left was this squeaky farting sound:cool:
    It was art man you should have been there. :bag:
     
  19. A more powerful amp would have gotten him there quicker! But not as much play time :D.
     
  20. 1958Bassman

    1958Bassman

    Oct 20, 2007
    Did you listen to which driver was clicking when you connected the battery? If it was the tweeter/horn and the click was very quiet and only happened once, try it again, but connect the speaker terminals with a wire, screwdriver or any piece of metal. If you hear another click, it means that speaker has a filter cap inline and the cap is good. If you hear just a click from the bass driver, it may be toast. In that case, remove the driver, set it on a flat surface and gently press on the cone with your fingers evenly spaced. If it doesn't want to move, don't force it. If it crunches when you move the cone, it means the voice coil was damaged.
     

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