"Jim Lesurf"
Arny Krueger


However, presuming that an ESL is necessarily an unusually capacitive
load is not always correct.

That's true. However the old Quad ESL (57) tended to behave like a
microfrarad or two in the treble range.

** Completely wrong.

One cannot "simulate " an ESL 57 with a single capacitor of any value.


And in the UK for decades that was
what people took for granted was meant by 'ESL' despite some other models
being marketed at various times. I suspect that was why for many years
both
UK reviews and some engineers tended to use a 2.2uF cap as a quick
simulation.

** That test was always stupid and wrong and still is.


That said, above c20kHz the impedance tended to turn over.


** Gobbledegook for it began to rise sharply above 20 kHz.


So the test was
quite likely one of surge current survival as much as stability.

** That test was always stupid and wrong and still is.

As previously posted in this thread - the REAL issues with amps driving
the ESL57 or similar are at LOW and sub-sonic frequencies. The input
transformer easily SATURATES !!



..... Phil