Michael Karas wrote:
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There are very many speaker driver applications that are DC coupled to the speaker leads.

We are not talking about DC coupling per sae, we are talking about DC driving, which is different.

Of course in a DC coupled amplifier, by proper biasing and feedback any DC across the load is virtually zero. The 300 W class a-b power amps I designed for my hi-fi are also direct coupled from source to output - but there is a massive DC detecting crowbar circuit that is there "just in case" the mean DC on the load gets to more than around 10mA. The only time they have blown is when my friend attempted to drive my sub-woofers with a super-duper all digital 1812 overture- which clipped the cannon bits to the supply rails. That blew out the DC detect stage and shut the amp down.

As a lesson in design, which this evidently is, I reckon that the amp should essentially be biased off by default, thats all. It is just an anti-bugging device.

Steve