From: mark_zacharias@labolgcbs.net   
      
   "Trevor"  wrote in message   
   news:m6asds$39i$1@speranza.aioe.org...   
   > On 10/12/2014 11:21 PM, Mark Zacharias wrote:   
   >> In my experience the manufacturers are simply trying to reduce the   
   >> number of warranty repairs to some extent by specifying the higher   
   >> resistance. In truth, with a bit of common sense applied at the volume   
   >> control side of the equation, a four-ohm speaker will work just fine   
   >> with any solid state amp or surround receiver of even minimal quality,   
   >> such as Pioneer, Sony, Marantz, Denon, Kenwood, etc PROVIDED as I say,   
   >> some common sense is used and the user isn't trying to use the thing as   
   >> a sort of mini-PA system.   
   >>   
   >> Problem is, people connect all sorts of speakers, even for example car   
   >> stereo speakers wired in unusual, often incompetent ways, then expect to   
   >> be able to blast away for hours on end.   
   >>   
   >> Yamaha, for example, knows full well that one of their power   
   >> transformers will not have a failed thermal fuse in the power   
   >> transformer in the absence of customer abuse - playing the thing at a   
   >> very high level, probably with low impedance speakers (or combinations   
   >> of speakers) for an hour or two more or less continuous.   
   >>   
   >> Therefore, they will only cover ONE power transformer under warranty.   
   >> The warranty servicer is expected to educate the customer that a second   
   >> transformer won't be covered.   
   >>   
   >> In fact, the newest Yamaha's will "rat out" the user by recording how   
   >> high the volume was for more than one minute and how many times. This   
   >> info is accessible in the service menu.   
   >   
   >   
   > Amazing isn't it that a manufacturer can incorporate watch dog electronics   
   > in a receiver, but not simply a more sophisticated protection circuit to   
   > prevent damage in the first place!   
   > I'd be looking elsewhere if that's the case.   
   >   
   > Trevor.   
   >   
   >   
      
      
   Oh, they have protection circuitry all right. Lots of triggers all monitored   
   by the microprocessor. Problem is, since music can be extremely dynamic in   
   nature, and since transistors can be destroyed so quickly, any circuit that   
   would absolutely prevent damage to output transistors caused by abuse, would   
   also protect the amp from being able to produce music at any decent level.   
      
   Some manufacturers are now monitoring temperature of the power transformer   
   as well, but I've already seen one where the transformer was not saved from   
   the internal thermal fuse opening.   
      
   They're getting better, though - I'm seeing fewer and fewer blown channels   
   due to abuse these days.   
      
      
   Mark Z.   
      
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