dB Technologies Opera 405D

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Hi,

I am very new to this Class D amp, and have a basic understanding of the theory of operation. A friend of mine asked me to have a look at this amp. It is a 2 way powered speaker. When I switch on, there is a very loud hum from the woofer. I then disconnected the woofer and the tweeter is working fine. I measured the voltage across the woofer output terminals and it was reading 28v DC. I also measured the voltage across the tweeter, when I switch "ON" , firstly it shows a reading of also 28v DC across the tweeter and then within a second or two, when the sound comes out, the voltage disappears across the tweeter. I guess it is a half bridge. Can anyone with a knowledge of class D help me with this.

Thanks

Carlos
 
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