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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. Mark C.

    Mark C. Supporting Actor

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    I can't believe some of the responses in this thread. The guy blows out two $1,000-plus receivers because of a fault in his own speaker cables and we're supposed to blame the dealer and Rotel? I damaged my Rotel pre/pro a few years ago. It was my own fault. I accidentally shorted the unit by moving around speaker cable terminals without powering down the unit. My Rotel dealer fixed it under warranty even though he, and Rotel, didn't have to. It could have easily been me eating the cost of repair.
     
  2. Jake S

    Jake S Stunt Coordinator

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    exercise the same caution as you would when handling jumper cables
     
  3. Brad_Harper

    Brad_Harper Stunt Coordinator

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    Not having "current-limiting" is just a huge mistake in any amp design. Properly designed current limiting circuits will have absolutely no effect on sound quality. Nobody needs to be able to arc weld with their amp. A properly designed current limiter shouldn't kick in until it sees very low impedances
     
  4. PhillJones

    PhillJones Second Unit

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    So we have a disagreement.

    I must say, I find the reasoning that thermal circuits cause distortion when your driving your amp so hard it's about to explode a little weak. Surely if it's being driven too hard, it's good that it's distorting, at least you get some audiible warning before the smellable one.

    I guess some receivers will be well protected and other won't, depending on the oppinion of the manufacturer. I'll have to just ask at the dealer individually. What it really boils down to is finding an amp in my price range, ie
     
  5. Yogi

    Yogi Screenwriter

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    What about the very popular Denon 3805? Seems like its incredibly flexible and a good value for HT receivers.
     
  6. EGM

    EGM Stunt Coordinator

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    Phill,

    I second the Denon 3805. I have one paired with B&Ws all around and it sounds great with a tremendous amount of bells and whistles that one would look for in a home theater receiver. Musically it is very solid, not as good as seperates naturally, but very clean with good detail and midrange.

    GM
     
  7. PhillJones

    PhillJones Second Unit

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    Thanks guys, I'll check out the Denon this week-end.

    Finding a dealer is hard isn't it. I'm going to have to go to Tweeter I think.
     
  8. Kenneth Harden

    Kenneth Harden Screenwriter

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    Rotel is a big company (in terms of making protection systems), and that is unnacceptable.

    Every receiver (cheap) I know of has protection circuits, from low ohms, to shorts, to thermal. Even the $87 Wal*Mart HTiB systems have at least the basic systems.

    Could you even get UL approval with no protection?
     
  9. Mark C.

    Mark C. Supporting Actor

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    If Rotel had "no protecton'' you'd have units blowing up left and right. Obviously, that isn't the case. So let's jump off the outrage wagon. The original poster's shorted speaker cables had a lot to do with this.
     
  10. James W. Johnson

    James W. Johnson Screenwriter

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    I am sure many would disagree with this statement, alot of well respected Pro amps have this feature and many Professional users leave it disabled.
     
  11. PhillJones

    PhillJones Second Unit

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    Well, obviously shorting out the speaker wires is what caused it. But if the question is, does the receiver have protection against being shorted, then the answer is obviously no or it wouldn't have blown.

    I've now bought a denon, which appears to go into some kind of protection mode when you first turn it on. I'd like to know if this would protect the amp from a dead short but can only think of one way to find out and I'm not about to do that.

    If it wouldn't protect it, I may as well take advantage of th 30 day home trial thing and gt myself a Rotel. If it would protect it, I need to think about what's more important, sound quality or protection against accidents. So many people here have said that they've accidentally crossed wires themselves that I'm not prepared to accept that it's just me being an odiot and that this isn't an issue for people who are more Hi-Fi savvy.

    Phill
     
  12. Yogi

    Yogi Screenwriter

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    I dont understand why.[​IMG]
     
  13. PhillJones

    PhillJones Second Unit

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    Don't most amps do this? I know my dad's 2 channel power amps do it. When you turn it on, no sound comes out for about three or four seconds. Some amps I've seen have a light that says 'protection' next to it. My Denon, flashes the power light on and off. It does this even if nothing is connected and it hasn't exploded yet so I guess it's fine.

    I suspect that it's testing the imedence presented on the speaker terminals before the relays connect the power amps.
     
  14. EGM

    EGM Stunt Coordinator

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    Phill,



    My 3805 does this too...I didn't realize that was what it was doing, but now that you mention it, that sounds right.

    Congrats on your purchase!

    GM
     
  15. Yogi

    Yogi Screenwriter

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    Thats just everything initializing, thats all. No protection mode going on there.
     
  16. Michael R Price

    Michael R Price Screenwriter

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    Um, normally a power amp with no protection makes sound right away or within a fraction of a second. Sometimes this is accompanied by a turn on pop. If you get silence for a few seconds then a "click" and the sound comes in, that's a delayed turn-on circuit working. I believe most receivers have a function like this, though some use electrical muting in the preamp and not a relay at the output.
     
  17. PhillJones

    PhillJones Second Unit

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    Right, I've spoken to Denon and Rotel and here's the official answers.

    Denon's answer, paraphrased
    During that first few seconds, what I called the protection mode on the Denon, it nonitors the voltage on the output emitters beofer engaging the amps. If the voltage is too high, the impedence must be too low and receiver does not allow itself to be turned on. This is short circuit protection and is a common feature of AV receivers.

    Rotels answer paraphrased
    You can't put as much protection on a receiver as you can on an outboard amp. There is therefore NO short circuit protection on the rotel receiver. It does have thermal protection which may sometimes protect it from being driven too hard or having too low an impedence presented to it, it will not protect it from a dead short.

    So there you have it, you pays your money, you takes your choice.
     
  18. Yogi

    Yogi Screenwriter

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    Hmmm, Phil that tells me to avoid Rotel in the future. I wonder why Rotel doesn't put a $10 protection in its AVRs inspite of saving a ton making them in China, while Denon does it inspite of manufacturing its AVRs in Japan?
     
  19. Rogozhin

    Rogozhin Stunt Coordinator

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    Must be the gossamer of pseudo-science.

    Rogo
     
  20. Yogi

    Yogi Screenwriter

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    [​IMG]

    BTW Phil, how does the 3805 sound compared to the Rotel?
     

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