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I just blown up two amps in one week-end

Discussion in 'AV Receivers' started by PhillJones, Aug 16, 2004.

  1. Brad_Harper

    Brad_Harper Stunt Coordinator

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    This all depends on how the rest of the amp is designed. If the output stage is full of Bipolar transistors then your repair bill could be rather large. Bipolars fail shorted and can cause cascade failures throughout the amp.
    Unless you see smoked or burnt components it is impossible to tell visually if the BJT is ok or not. Often it is best just to scrap every BJT in the circuit and start over.

    As far as sound quality goes I have to agree that protection circuits will have no effect. Properly designed ones are not in the circuit path of the sound info until a short occurs. Just having Thermal protection is not the best way to protect your equipment. In the Levinson case Phil's speaker would have been ruined because of the high current value going through the speaker. All amps should be designed with current limiting circuitry for the best possible protection.
     
  2. Lee Distad

    Lee Distad Stunt Coordinator

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    I have to confess, that I am deeply dissapointed that Mr. Jones passed up on the chance to use the phrase "They blowed up real good!"
     
  3. Michael R Price

    Michael R Price Screenwriter

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    Brad, that's a bipolar amp. [​IMG] Mosfets fail with a catastrophic short circuit, too. You have to check the other components because it is possible they would be damaged, but usually nothing really bad happens because the currents in the rest of the circuit are intrinsically limited.
     
  4. PhillJones

    PhillJones Second Unit

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    Brad, funny you should say that. The first amp was very much a cascade failure. It would have been extreemly cool under different circumstances. As Lee said, it blowed up real good. The second one was more just your wiff of smoke. I suspect that it would be an easy, cheap repair but it's too late for that and the dealer seemed to be not interested in helping me figure out what needed doing to it.

    Yogi, I know of another dealer I can get a lift to in Framingham, but the more I think about it the more convinced I am that I should buy another brand as this model of Amp blows up if the wires get shorted out by accident. I'm certainly going to do some more auditioning and ask some other dealers about protection circuits.

    I don't know, there are two possibilities. 1) It's to be expected on these fancy AV receivers 2) Rotel are rubish. I keep changing my mind on which one I believe.
     
  5. Jorge M

    Jorge M Stunt Coordinator

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    Phill, are we talking about Spearit Sound on Comm Ave?
     
  6. PhillJones

    PhillJones Second Unit

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    I don't want this thread to turn into a series of recriminations.

    I've altered my original post to be absolutely precisely exact about what was said compared to how I felt about it. Please re-read it as there is an important distinction between made to feel like your not welcome and being told so.

    Quite frankly, I wouldn't sell me an amp either.
     
  7. Charlie C

    Charlie C Stunt Coordinator

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    phil, I wouldnt worry about bad mouthing any store, this is an OPEN forum. Seeing as it was a user fault anyway, this should absolve the retailers of any wrong doing. Im sure they think of you as the amp killer, but they had to process paperwork AND EXPLAIN to Rotel why they were sending back 2 new 1056's. I would not have been as friendly as some suggested they should have accted, and neither would you, given the situation in reverse. now if they dont want your money, screw them, you obviously have some $ to spend and they are obviously in the buisness to make money. If they are the ONLY Rotel dealer in your area and you are a dedicated Rotel customer, you should have had a history with them, and they may have helped you figure out the problem the first time it happened.
     
  8. Dan J S

    Dan J S Agent

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    You can't fault the dealer. He did get his money back, and now has the opportunity to take his business elsewhere and buy an amp that is not (literally) one inch from frying at all times.
     
  9. PhillJones

    PhillJones Second Unit

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    Charlie,

    I used to be a dedicated Rotel kinda guy but I'm new to Boston. I immigrated in january.
     
  10. Charlie C

    Charlie C Stunt Coordinator

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    "I'm new to Boston"
    well maybe you can get one at the place yogi suggested in CT

    if you still wanted the rotel model
     
  11. EGM

    EGM Stunt Coordinator

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    Real Name:
    Galen
    Phil,

    I thought there was a dealer in Harvard Square? I could be wrong, but the last time I was in Boston I was staying at a hotel in Harvard Square and I walked into a high end shop that was in the top floor of that big indoor pseudo-mall that caters to Harvard students. Was kinda small...but I thought he carried Rotel. There is also a Tweeter out there if you decide to go in another direction like Denon, Yamaha or B&K.

    GM
     
  12. Jerome Grate

    Jerome Grate Cinematographer

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    Phill, hope I got this straight, amps are fried, the dealer relunctally took them back, but took them back nonetheless, and you are dead set on getting some more Rotels from another dealer.

    If that's gist of the story, if it is then I can certainly understand your desire for the Rotels and that's cool, but if the amps don't provide any real protection against shorts, why take the risk of frying more of them. Even if you fix the short in the speakers, I can't help but think that you will be listening to movies and music on pins and needles. From me looking in from the outside I think you will always wonder if you are running what you are listening to too loud. I'm pretty sure these amps weren't cheap and maybe you can look towards Outlaw for a 5 or 7 channel amp.
     
  13. PhillJones

    PhillJones Second Unit

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    Galen, thanks for the heads up. I'll check them out, even though I'm not going to go with rotel now.

    Jerome,

    You're right this thread has really served the purposed it needed to in talking me into abandoning the Rotel model. I was considering the Outlaw's but am I right in thinking that they have no dealers at all. I'd like to listen to it before buying it.
     
  14. Jerome Grate

    Jerome Grate Cinematographer

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    You know, for critical listening and we're all critical listners we would of course want to hear what we are buying in that area, but not unheard of to do a blind (or in this case a deaf) purchase. There are plenty of reviews for and against Outlaw, and enough info on the reliability of the products. I bought my speakers unheard and to me they sound better than the Polk speakers I was about to right a check for. There are plenty of Outlaw owners on this sight and I think Outlaw has their own forum, get the responses and make the decision.
     
  15. PhillJones

    PhillJones Second Unit

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    Before I connect any other Amp, I'm going to test the speakers and wire by connecting a multimeter to one end.

    Can somebody who knows talk me through what I need to do.

    Also, the plasma screen showed up today. It has speaker terminals on the back. It says in the instructions that they're for the speakers that pioneer make specifically for the screen. The terminals are labeled 8-16 Ohms. So I'm guessing it is actually safe to connect my 8Ohm Tannoy floorstanders to the terminals on the back of the plasma? I know that impedence varies with frequency and 8Ohm speakers look like 4Ohms to DC. Does this mean that, since the Speakers are just on the edge of the spec, it's a bit dangerous? This would tide me over till I can choose a new receiver but I don't want to take any risks.

    Excuse me for asking dumb questions. I am a touch gun-shy at the minute. It took me a good hour to install the video card and turn my plasma on. :b
     
  16. Jake S

    Jake S Stunt Coordinator

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    But a short in the speakers (before the voice coil), is the same as a short in the speaker cables, is it not? Every amplifier should have protection against this because of how easy it is to accidently touch connectors together.

    """""""""""""""""""""end of quote""""""""""""""""
    actually , only "current-limiting amp designs" will have thermal protection and it is the design that limits currect output and headroom.....bad idea for sound quality.

    non-current limiting designs ussually have little protection unless they use fuses and fuses aren't always enough, but I would rather be carefull with my hook-up ...and not stupidly throwing a dead short to my amp and thus be rewarded with many times the available current to my speakers!
     
  17. PhillJones

    PhillJones Second Unit

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    So Jake. You're saying that whatever receiver I get, it won't be protected against a short circuits?
     
  18. Jake S

    Jake S Stunt Coordinator

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    no, rather ,the ones with the best protection (generally) are the lower-end mass market pieces..the better "audiophile" grade mnfgrs belive that tweaks would give up a little safety for much improved performance.....
     
  19. Peter_LM

    Peter_LM Auditioning

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    Hi Phill,

    What a nightmare!! This may be a silly question, but how are your speaker wires terminated (at both ends)? You have a much higher chance of a short with bare wire, as a stray strand of copper from one or more cables in contact with the back panel of the amp or another wire could cause a short. On the other hand, if you terminate your cables with decent quality banana connectors you eliminated this scenario altogether, because there is no exposed wire at any point.

    I may be stating the obvious, but since you didn't mention this, I thought I'd bring it up.

    Hope this helps.
     
  20. Mary M S

    Mary M S Screenwriter

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    Dear Phantom [​IMG]

    I would encourage a test demo of Outlaw products. I too in my past preferred to see/hear something first. Had want it now ittis, and was extremely leery of mailordering electronics.

    My first purchase was to acquire one sub at a local ‘boutique’ (really a audio design/install dealer) which turned into a 7.1 speaker purchase The intimidation factor I felt trying to go in (a female) and mumble my questions was extreme. I would rather make mistakes/ask/learn than hang on to any dignity, which would buffer me from learning. Not understanding how to say it (or what to ask for) should but does not discourage me too badly. They were polite, courteous but barely holding back snickers over my struggles to research what I was getting into. In fact the techs at the loading dock asked me when I picked up the speaker order why I was not having them installed, repeatedly stating “We Guarantee! You’ll be back to have us do it”
    If the thinly veiled humor had been for and with me, (love a joke even if it’s me!) I would have “been back again’ when I upgraded my mains to something which cost quite a bit more than my entire first 7.1 speaker purchase within the next year. But I never returned (not for install; nor even a question) and gave up the discount I could have pressed for in 'loyalty' future buys at this location to do business where I could felt more comfortable. (and was taken halfway seriously)

    I’ve had to return products I have demoed a couple of times since that ‘first’ boutique buy at various B&M electronic stores. The hassle of doing that is not any easier (in my book) than mailing back and forth.
    In fact depending on the ‘return’ line and policies at some of these places, I am beginning to much prefer the shipping process, which arrives (at least one direction) at my doorstep. The only drawback I see is being responsible for the shipping charges both ways. The lack of tax on these larger out of state purchases compensates by reducing cost more than shipping charges increase. I also note B&M restocking fees are becoming more prevalent.

    Outlaw, (and their forum) laughed with me, answered every question and took (my serious ones) seriously.
    Were absolutely invaluable to me, in my first steps in audio. I can ‘hear’ as well as the next audiophile although I am still sorting (will be hopefully for years future) what and how gets the ‘sound’ best from point A to B. I have listened with increasing (hopefully more discriminating) understanding to many units since and during my first purchases almost 3? Yrs ago.
    I find Outlaw products extremely hard to beat. So much so, I currently own 2 950’s. One of their discontinued 5-channel amps and a 770 amp and have no intention of upgrading in these areas. (though the bug bit hard in video and speakers and STB’s and players)

    I’ve read too many posts from contented Rotel owners to discount lightly products from that manuf. I feel they are a good line. Although I have finally satisfied my desire to hear Rotel, which further reinforced my choice to stay with Outlaw currently. But as you have posted that you are willing to look elsewhere, I cannot recommend highly enough giving Outlaw a demo.

    I am sold on demo’s of direct-from-manuf electronics even when factoring the occasional hassles of shipping. I’m keeping an SVS PC-Ultra I just purchased via web after some trial time. I’ve had great success in several of my purchases and these web-only product offerings shall always be included in my future upgrade considerations.

    Never heard an Outlaw receiver, (my 950’s are pre-pro’s) but I understand from following products a while, Outlaw recievers are considered quite beefy in power section.

    I have not blown up an Outlaw amp yet. (although I did just kill a sub [​IMG] ) I salute you! .. fellow traveler in the (pilots' #1 last recorded remark) "Oh @@@@" club.
     

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