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B&W ASW610 subwoofer burned out twice now

One of my two B&W ASW610 subwoofers last year experienced a circuit board overheat and burned out.  The fuse didn't protect the unit from whatever caused the burn out.  I use a PS Audio power cord into a PS Audio Power Port so I know it's not that.  My dealer ordered in a new circuit board from B&W and replaced it at their store.  All was well until just now today. I upgraded the cable today and when i went to unplug the unit, the circuit board burned again.  The odor was very strong and I know it's not the fuse. The unit is dead.  I have a mind to toss it out in the garbage but for what it's worth, anyone have any ideas as to why this subwoofer would burn out twice and my other ASW610 operates perfectly.  Same system, same room, they're both about the same age, etc.  It is a lemon?  What am I doing wrong?
pdn

Showing 3 responses by erik_squires

erik_squires
15,902 posts
 
OP - Don't get me wrong. That condition I mentioned is STILL very much a bad, or incomplete design, and it's just supposition.

It could be anything.


But yes, you can replace the amp with a nice Class D with a DSP front end, giving you expanded capabilities. :)
erik_squires
15,902 posts
 
There is a weird condition that happens in switching power supplies, not the amps.

The issue has to do with very short term power interruptions, in the neighborhood of 1-2 cycles of AC power, though by now I would not expect this issue to remain in professional devices. The issue is that the very short interruption causes the normally switched output transistors to turn linear. When they turn linear, they loose their 80-ish % efficiencies and turn 30-ish % efficiencies. In other words, they convert a lot more power to heat and burn themselves out.
I wonder if this is what the OP had?
erik_squires
15,902 posts
 
So every powered sub I know of uses Class D amps and they tend to be more reliable than this.

Wait, the failure occurred at the same time you removed the plug from the wall?
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