Phil Allison wrote:

The old test used to be something like a 2.2uF cap.


** Never was and still is NOT a relevant test of an
amp's ability to cope safety with an ESL speaker like the
Quad '57.


But TBH you would be
better experimenting by trying various capacitances,

** Absolute CRAP !!


What happens will depend entirely on the amp design.


** And has nothing to do with Eiron's dopey question -
****HEAD


There's a suggested dummy load he

http://www.quadesl.com/graphics/quad...cs/ampload.jpg

which I found he

http://www.quadesl.com/quad_ref.html

But there's no accompanying text. Seems to lack primary and
secondary winding resistance, but I don't know how
significant they are.

No info on how true it might be outside the audio band,
either, but presumably it's intended with stability testing
in mind, although maybe what's OK for testing a typical
valve amp may not be adequate for testing an SS amp with a
wider bandwidth.

Hopefully not another red herring (which are smoked, BTW, so
fishing for one would be even more futile than a wild goose
chase).

Ian

Arny wrote:

I think we have been this way before. If I recall, the
answer is that a capacitor is not a realistic reactive
load.

It certainly is not a good simulation of just about any
real-world speaker.

However, the mission of a modern power amp is to live on,
even when abused. A good map lives on and thrives when
presented with a seriously off-the-wall load like a really
low ESR 2 uF cap. If you do a good job on the stability
and SOA fronts, it becomes just another non-theat.

It's a "non-threat" anyway.

My amps have less chance of being connected to 2uF than they
have of being bombed, swallowed up by an earthquake, struck
by lightning, and washed away in a mudslide.

To protect them against these possibilities would compromise
their performance, so I choose to live dangerously.

Ian