Spot the Design Error

What's absurd about shutting down an amp when the fet junction temp hits some limit? What would be a better protection than that?

There are self-protecting fets that have built-in over-temperature protection, but the ones that I've tried were bad in other aspects.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

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** Planet Larkin must be undergoing an eclipse...

... Phil

Are you talking about like Pioneer receivers that had the drivers fed with a higher voltage than the outputs ? And the way I see it there is no reason it has to be class A.

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• No.

** Bootstrapping the class A stage load has been standard practice since the the early 1960s. It linearises that stage and acts just like boosted rail with a current source.

The negative side boost rail is needed because of the "cascode" drive topology. Would not be able to drive the PNP output devices into full conduction at negative voltage peaks otherwise.

The amp meets all specs easily, 0.002% at the 1W level rising to around 0.01% near full power.

The problem is something amp makers almost never spec.

.... Phil

Phil Allison wrote in news: snipped-for-privacy@googlegroups.com:

I have been a fan of, and have bought Pioneer audio products all my life. They are a well priced, well engineered, consumer level product.

I even bought my first LaserDisc player from them. My first LaserDisc player was a pioneer disc player recovered from a video game. It was a "Mach I" where the player would no longer deliver the game's data streams correctly. But it played video discs just fine. That player contained my first laser optical bench, as it actually had a nice HeNe 8 inch tube laser in it. And two steerable mirrors, which I quickly adapted to handle music and put lissajous patterns on the ceiling with.

Slew rate ?

The DC-300 was being made at a time when most amplifiers actually did what they spec'd (typically)

Crosstalk ?

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** Massive non sequitur.

Pioneer = Pee - on - err.

..... Phil

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** Hardly likely.

That is what we get here all the time.

.... Phil

Obviously the thing oscillates ultrasonically, destroying tweeters and annoying local dogs. But there are so many possible feedback loops in that schematic that I don't mind admitting I don't see the mechanism in question.

Good puzzle, though. I look forward to seeing the answer revealed at last. It *will* be revealed at last, right?

-- john, KE5FX

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** The Crown DC300A is renowned for being completely stable and "bomb proof".

Plus, despite malicious rumours to the contrary, was not designed to drive the motor in Crown forklift.

** Yes.

And the reveal will probably incriminate a bunch of modern audio amps as well.

.... Phil

Phil Allison wrote in news:24d8b79a-6f48-444b- snipped-for-privacy@googlegroups.com:

my

Only time that ever happened, she asked for it.

Anyway, I did say consumer level product, not audiophool level gear.

Back then, they were more concerned with low distortion amplification than Sony or Panasonic or other folks *at the time* were.