"Dave" ) writes:
"Eeyore" wrote in message
...


Dave wrote:

"Arfa Daily" wrote in message

Now there's your problem with a DC coupled amp ...

why do you think it's a DC coupled amp? All I see in the description is
"Kenwood".

It would have to be pretty ancient to be AC coupled.

Graham


Are pretty much all modern amps DC coupled, then, as opposed to capacitance
coupled? My solid state amps are from the golden era high-powered SS audio,
mid-70's to early 80's and both amps and my preamp have capacitor-coupled
inputs.


You are misreading the terms.

IN the days of tubes, pretty much all the stages were coupled either by
capacitor or transformer. A shift in DC in one would not affect the bias
of the next stage, unless the coupling shorted out.

When transistors came along, amplifiers followed that scheme. But it
didn't take long before they were going to a different system, a multiple
active element amplifier where the elements were directly coupled to the
next and the capacitors were only at the input and output. When they
started running them off a split supply (ie plus and minus some voltage)
the output capacitor wasn't even needed, since the idling point was zero
volts.

But in those, if a transistor went bad, or the bias on one transistor
shifted, it would affect all the rest. You were no longer dealing with
a single stage (it's easy to figure out what's wrong when there's only
one active element, and even easy to figure out which active element
is the problem) at a time, you were looking at a much bigger picture.

Michael