High Frequency Tone, Blown Tweeters.

VSAT88
VSAT88 Posts: 1,260
in 2 Channel Audio
Want to throw this out here and see what some of you say. I had posted a long time ago about a Parasound preamp I had hooked up to an B@K EX-442 that malfunctioned and sent a high frequency tone to my Polk SDA-SRS2's and blew all 4 tweeters. Seems like I may have been totally wrong in blaming the Parasound preamp as with the same amp (EX-442) and a totally different preamp (Yamaha AX-900) it has happened again. This time blowing both tweeters in my Snell J/III's. I had noticed what sounded like a ground loop or distortion of some kind in the speakers so I went to the preamp and turned it off then turned the B@K off then re seated the phono/RCA cables from the preamp to the amp and when I turned it back on once again a incredibly loud tone and two blown tweeters before I could get my hands to the power button. Any ideas as to what might have caused this ? This tone/sound is so loud that it hurt my ears and they are still ringing next day. I am going to act like a total noob on this one and listen to what you guys have to say and do whatever you recommend step by step. I am going to act like I know nothing whatsoever and you tell me what you would do. I have all the test equipment besides a distortion analyzer and a spec a.
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  • mhardy6647
    mhardy6647 Posts: 33,909
    edited February 2019
    So -- wait.
    You got this noise ("tone") with the volume control(s) on the preamp(s) set to zero?

    My initial guess is amplifier instability causing oscillation -- but it's just a guess.

    Another guess-- powehaps the "root cause" could be a bad cable (or cables) causing an open circuit at the amplifier. I guess (?!?) some amplifiers don't like open circuit inputs -- I learned this in @Clipdat's thread. I gave him some bad advice :(

    https://forum.polkaudio.com/discussion/184388/amplifier-static-click-pop-through-speaker-when-turning-on-off/p1
    mhardy6647 wrote: »
    Troubleshooting 101. If a change is made, and something different happens - the change is more likely than not the source of the "difference".

    If you have a source with its own attenuator, bypass the preamp entirely and see what happens. Heck, if you want, you can disconnect everything from the input of the power amplifier, turn it (the power amp) on - let it come up to operating 'speed' - then turn it off and see if it clicks/pops/whirrs/whatever. :) Short the inputs, if you wish -- this should be the 'deadest' (quietest) operating condition for the power amplifier (and they way they're generally tested for quantitative performance analysis by, e.g., Stereophile).
    ...
    Clipdat wrote: »
    I just tried turning the amp on with no RCA cable attached to it and it made a thump on power on and then there was a loud buzzing and hum coming through the speaker.

    I guess these don't like to be turned on with no cable attached?

    Apparently the mfgr. did confirm that the amps can't be run with open-circuited inputs -- but I'll be darned if I can find the quote in that post :(


    At any rate, take any advice from me with a big ol' grain of salt!!! :#

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  • VSAT88
    VSAT88 Posts: 1,260
    Far as I know yes, the volume was turned all the way down when this happened. I am going to check the interconnects as well. Keep firing off the items to check.
    Thanks.
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  • pitdogg2
    pitdogg2 Posts: 25,576
    edited February 2019
    take the sda cable off. something is not common ground...

    I had a Yamaha AX-900 great little integrated amps.
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  • VSAT88
    VSAT88 Posts: 1,260
    No SDA cable. Not using the SDA's now. Had Snell j/III's hooked up.
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  • pitdogg2
    pitdogg2 Posts: 25,576
    my bad I had read over that. something is fubared in the amp. it is the only common item used in all aspects.
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  • VSAT88
    VSAT88 Posts: 1,260
    I think you are right. I was hoping to get as many options of things to check as possible then run thru them each at a time. To be honest I love this amp but now I have went thru 4 RD 0194's and two D26TG-05's . That is about how much I have in the amp $ wise and I am kind of pissed in a way so I do not want to go off 1/2 cocked in a whirlwind taking everything apart and missing something simple. Thanks.
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  • motorstereo
    motorstereo Posts: 2,145
    Loose turntable ground wire on the phono input? I had that happen once and ruined some tweeters even though the volume was turned down.
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  • VSAT88
    VSAT88 Posts: 1,260
    Good thinking. I wish. No TT hooked up. It was PC to Modi DAC to CD in Preamp to Amp....I think this thread has the plague anyway...Cannot believe so few have chimed in with possibility's. Thanks to all who have !
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  • mhardy6647
    mhardy6647 Posts: 33,909
    It's a weird symptom. Hum, buzz, hiss, noise -- all those are pretty commonplace. High frequency, loud sounds suggests feedback or oscillation (which, when it comes to hifi, amounts to out-of-control feedback).
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  • Clipdat
    Clipdat Posts: 12,953
    Were the interconnects the same both time? Unlikely, but just curious.

    I think the amp is just shitting the bed.
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  • audioluvr
    audioluvr Posts: 5,603
    Any time you swap out inputs you should mute the pre, turn off the amps, count to 10 then turn off the pre and input sources. Now give them all a couple of minutes to drain the capacitors before swapping. Don't ask me how I know
    Gustard X26 Pro DAC
    Belles 21A Pre modded with Mundorf Supreme caps
    B&K M200 Sonata monoblocks refreshed and upgraded
    Polk SDA 1C's modded / 1000Va Dreadnaught
    Wireworld Silver Eclipse IC's and speaker cables
    Harman Kardon T65C w/Grado Gold. (Don't laugh. It sounds great!)

    There is about a 5% genetic difference between apes and men …but that difference is the difference between throwing your own poo when you are annoyed …and Einstein, Shakespeare and Miss January. by Dr. Sardonicus
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  • VSAT88
    VSAT88 Posts: 1,260
    Oh, believe me it was loud as hell, both times it happened. The first time it happened was about a year ago when it took out all four RD 0194's in the SDA's. Now it happens again ??? The interconnects were different both times it happened. The only common denominator being the PC/DAC and the Amp. the interconnects are new Mogami (2528) with Rean NYS373's connectors X 2 sets. Both 3ft. I did some quick continuity tests this AM. All I know for sure is that they have continuity/are not shorted. Far as waiting 10 seconds with the EX 442 I wait longer than that...This amp has 4 17,000 uF 75 V caps for main filters and no relay/dc protect at all so I need wait a good long while before re seating, unplugging/plunging back in any cable. I will say this now that I am thinking this thing over and not so hot under the collar...The reason I swapped out pre amps is that I took the EX-442 out of the system yesterday because I heard what sounded like transformer hum . Took the lid off and tightened the transformer bolt down and snugged all the rest of the screws and bolts while I was in there. While I was doing that I had the Yamaha sitting here so I put it in to have something to listen to while I worked on the EX-442. After I finished tightening up everything and lid back on I decided to listen to the pre amp section of the Yamaha integrated thru the EX-442 and not long after the fireworks went off. More I think the more you guys are all right. There is something wrong with the B@K. I am going to take it out to the shop tomorrow....
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  • pitdogg2
    pitdogg2 Posts: 25,576
    edited February 2019
    It is the only common denominator.... plus it's the only thing that can send DC direct to the speakers AFAIK
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  • delkal
    delkal Posts: 764
    edited February 2019
    pitdogg2 wrote: »
    It is the only common denominator.... plus it's the only thing that can send DC direct to the speakers AFAIK

    You can definitely fry speakers with DC but you will never hear it. You will see the speaker shift hard (one way or the other) and if the DC signal is strong enough it will then melt the coil. But if you hear it it Is an AC signal.
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  • pitdogg2
    pitdogg2 Posts: 25,576
    delkal wrote: »
    pitdogg2 wrote: »
    It is the only common denominator.... plus it's the only thing that can send DC direct to the speakers AFAIK

    You can definitely fry speakers with DC but you will never hear it. You will see the speaker shift hard (one way or the other) and if the DC signal is strong enough it will then melt the coil. But if you hear it it Is an AC signal.

    Interesting
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  • DaveHo
    DaveHo Posts: 3,536
    DC burns up woofer voice coils, not tweeters.
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  • mhardy6647
    mhardy6647 Posts: 33,909
    edited February 2019
    Right. The OP described a high pitched, loud noise. Good for cooking tweeters and characteristic of high-frequency ... umm... I've said it twice :)


    I am thinking it's the power amp, as well -- just a SWAG, though.
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  • VSAT88
    VSAT88 Posts: 1,260
    SWAG="a traveler's or miner's bundle of personal belongings" ?
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  • motorhead43026
    motorhead43026 Posts: 3,901
    edited February 2019
    ^^Australian definition.
    The best way to predict the future is to invent it.

    It is imperative that we recognize that an opinion is not a fact.
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  • VSAT88
    VSAT88 Posts: 1,260
    BTW @audioluvr I would love to hear those B&K monoblocks !
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  • audioluvr
    audioluvr Posts: 5,603
    edited February 2019
    VSAT88 wrote: »
    SWAG="a traveler's or miner's bundle of personal belongings" ?

    Sealed with a grope?
    VSAT88 wrote: »
    BTW @audioluvr I would love to hear those B&K monoblocks !

    Come on over!
    Gustard X26 Pro DAC
    Belles 21A Pre modded with Mundorf Supreme caps
    B&K M200 Sonata monoblocks refreshed and upgraded
    Polk SDA 1C's modded / 1000Va Dreadnaught
    Wireworld Silver Eclipse IC's and speaker cables
    Harman Kardon T65C w/Grado Gold. (Don't laugh. It sounds great!)

    There is about a 5% genetic difference between apes and men …but that difference is the difference between throwing your own poo when you are annoyed …and Einstein, Shakespeare and Miss January. by Dr. Sardonicus
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  • VSAT88
    VSAT88 Posts: 1,260
    Here we go again.............lol
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  • VSAT88
    VSAT88 Posts: 1,260
    SWAG= Sealed With A Gallon....Of Black paint ???
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  • audioluvr
    audioluvr Posts: 5,603
    Check for cold solder joints. Use deoxit on all 5 fuses and where the board screws to the top of the power caps. Start with that and test it on a crappy pair of speakers...
    Gustard X26 Pro DAC
    Belles 21A Pre modded with Mundorf Supreme caps
    B&K M200 Sonata monoblocks refreshed and upgraded
    Polk SDA 1C's modded / 1000Va Dreadnaught
    Wireworld Silver Eclipse IC's and speaker cables
    Harman Kardon T65C w/Grado Gold. (Don't laugh. It sounds great!)

    There is about a 5% genetic difference between apes and men …but that difference is the difference between throwing your own poo when you are annoyed …and Einstein, Shakespeare and Miss January. by Dr. Sardonicus
    · Share on FacebookShare on Twitter
  • VSAT88
    VSAT88 Posts: 1,260
    audioluvr wrote: »
    VSAT88 wrote: »
    SWAG="a traveler's or miner's bundle of personal belongings" ?

    Sealed with a grope?
    VSAT88 wrote: »
    BTW @audioluvr I would love to hear those B&K monoblocks !

    Come on over!

    Will do ! Hope you are California way. I always like a visit there.
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  • VSAT88
    VSAT88 Posts: 1,260
    audioluvr wrote: »
    Check for cold solder joints. Use deoxit on all 5 fuses and where the board screws to the top of the power caps. Start with that and test it on a crappy pair of speakers...

    Will do. Pool pump took a dive so...First things first. Down South here and already getting warm. Not like I don't have music to listen to !
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  • audioluvr
    audioluvr Posts: 5,603
    VSAT88 wrote: »

    Will do ! Hope you are California way. I always like a visit there.

    North of there. Just East of Portland in the Columbia River Gorge.
    Gustard X26 Pro DAC
    Belles 21A Pre modded with Mundorf Supreme caps
    B&K M200 Sonata monoblocks refreshed and upgraded
    Polk SDA 1C's modded / 1000Va Dreadnaught
    Wireworld Silver Eclipse IC's and speaker cables
    Harman Kardon T65C w/Grado Gold. (Don't laugh. It sounds great!)

    There is about a 5% genetic difference between apes and men …but that difference is the difference between throwing your own poo when you are annoyed …and Einstein, Shakespeare and Miss January. by Dr. Sardonicus
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  • mhardy6647
    mhardy6647 Posts: 33,909
    edited February 2019
    my belief is that SWAG is an acronym (as opposed to an initialism*)
    for:

    Semi
    Wild-
    A$$ed
    Guess

    YMMV* though

    ________________
    * An acronym is pronouncable; an initialism is not. NASA and SWAG are - at least potentially - acronyms. YMMV and FBI are initialisms. Unless, of course, you like to say wummmv and fibbie in the latter two cases... in which case, there's nothing I can do for you, really. :#
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  • VSAT88
    VSAT88 Posts: 1,260
    Hey, got a few minutes today to polk around under the hood of the amp. Nothing that surprising in there but after looking a while pretty close up with a headset and a mag lamp I spied a resistor that was tied on one side at least to one of the output/MOSFETs . It looked as if it was never soldered at all..... Soldered it properly but I am still gonna keep polking around to see what I may see. Think after I get it back up and running I may well go ahead and do a complete re cap and put in new bridge rectifiers as well. Those can caps are gonna be expensive ! Then, on the other hand my ears are still ringing from the last blast so I may need give it up...
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  • nooshinjohn
    nooshinjohn Posts: 25,448
    The trouble you may be experiencing relates to something called the "Brown Note".
    The Gear... Carver "Statement" Mono-blocks, Mcintosh C2300 Arcam AVR20, Oppo UDP-203 4K Blu-ray player, Sony XBR70x850B 4k, Polk Audio Legend L800 with height modules, L400 Center Channel Polk audio AB800 "in-wall" surrounds. Marantz MM7025 stereo amp. Simaudio Moon 680d DSD

    “When once a Republic is corrupted, there is no possibility of remedying any of the growing evils but by removing the corruption and restoring its lost principles; every other correction is either useless or a new evil.”— Thomas Jefferson
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