"Sander deWaal" wrote in message

"Arny Krueger" said:


It's pretty well known in the industry that the Krell
ratings sheet has been juggled by Krell. The 8 ohm power
rating was backed off, to create the impression that it
is an ideal amp and puts out twice the power into 4
ohms. If the Krell amp were rated more conventionally
based on those tests that Sander's buddy Middius hates,
there would be a different story.

You're forgetting that the Krell also doubles current in
2 ohms.

The point is that what doubles is not the amps maximum
current output but the amps spec.

The 8 ohms power ratings must be way, way underrated then.

Yup. If you derated the QSC in a similar fashion, it would
still be more powerful by far.

The input impedance of the QSC amp is rather low,
something to keep in mind when driving it directly from
an opamp's output.

Most conventional audio-grade opamps have absolutely no
problem driving a 1K load to 5 volts rms, let alone just
2. Ditto for modern preamps, whether vacuum tube or SS.

Then why does e.g. Sony advise to load their CD players
with at least 50 kohms?

They like to use small output coupling caps?

Real men use the digital outputs of optical players, anyway.

Their output capacitors are at
least 47 uF, so a low frequency rollof wouldn't be a
problem (for the math challenged, the -3 dB frequency is
then around 0.5 Hz).

I seem to recall that the output caps of my Sony CD player
were 47 uF, for maybe the first year... ;-)

The input sensitivity should have nothing to do with the
output load impedance, is this a typo, a mistake or does
the amp use such a high amount of global feedback that
the load has influence on the input? In the latter case,
problems might arise with strongly reactive loads, and
this may make for a different sounding amplifier.
I also noticed the DF isn't specified.

Shows that Sander can't see that the amps input
sensitivity is scaled to its output ratings into various
load impedances.

********.

Do the math.

A good amp is a constant voltage source, regardless the
load.

Agreed, as is the QSC.

That means the load should be of no consequence to the
input level. If there is influence, it's a bad design.
Simple as that.

You're misinterpreting the spec.

There are more issues to discuss, but that would require
more information about both amps, and, preferably, the
schematics.

Looks like having Sander comment on power amps is like
engaging the proverbial loose cannon.

You think the specs Mike gave are enough to determine
whether these amps will sound the same in a DBT,
regardless the load?

Nope, but I've measured enough QSC amps to know how the
unspecified performance areas are.

Don't make me laugh.

Well Sander, I can't get you to even do simple math....