On Fri, 26 Nov 2004 09:02:55 -0000, "JustMe" wrote:

"Stewart Pinkerton" wrote in message
.. .
On Fri, 26 Nov 2004 02:32:02 -0000, "JustMe" wrote:

The pre/power amps are currently driving a pair of original Mission
752s
which together sound staggeringly good.

This prompts me to see if I can find data on the impedance of the 752s
as
that may be relevant here.

They are known to be efficient - 91dB, nominally 8 ohms on paper. I don't
have data beyond that, but they were well-reviewed in their day (mid
90s),
so I'm sure there's plenty of into out there. IIRC HiFi World listed them
as
"valve-amp friendly" for their efficiency.

IMNVHO, the best speaker they made since the original Chartwell-driver
batch of 770s.

I haven't heard every speaker that they have ever released, but have heard
most from the last 10 years and many from the years before.
They are - to my ears - the best speakers Mission have made to date.

The original 770 was *very* special, and made the company's
reputation. Interestingly, after Chartwell went bust, Mission never
did get that same sound back into the 770, despite several
incarnations with different drivers, crossovers and cabinets.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Fri, 26 Nov 2004 14:04:22 -0000, "JustMe" wrote:

Jim Lesurf wrote:


I think others have already explained this apparent puzzle in detail.
But, to confirm, yes, the problem may be that the amp in question
cannot deliver sustained (or peak) currents high enough to allow the
power to double.


Jim, John and Stewart, thanks for the explanations. I may have to hit
the books again, I can't believe how much stuff I have forgotten!

Alas, I can confirm that the older you get, the more you forget. :-)

Slainte,

Jim

Surely you have learned more *to* forget?

That's always the plan! :-)
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Fri, 26 Nov 2004 09:52:54 +0000 (GMT), Jim Lesurf
wrote:

In article , JustMe
wrote:

"Chris Morriss" wrote in message
...
In message , Stewart
Pinkerton writes
On a point of information, Krells before the KAV series were always
specified as doubling rated power right down to 1 ohm. This isn't
repealing the laws of physics however, as my '50 watt' KSA-50 mk II
actually puts out 105 watts into 8 ohms, 195 watts into 4 ohms, and
does indeed drive 440 watts continuously into a 1 ohm load.

Not staying in Class-A of course :-)

The Kraken amp is Class-A, BTW - it just occured to me that most people
here are not familiar with it and I that I haven't mentioned this
previously.

Again, this is an area where the reviews are 'unhelpful' as they give no
real indication of the quiescent current level, or the output current up to
which the amp remains class A.

If I guess and assume +/- 35 V rails and a quiescent of 1 A, the power
dissipation per channel comes out at about 70W. I am not at all sure if
that fits with a working temperature of around 55 C or not. But if the
values are of that order then it is probably essentially operating in class
A with the kind of speakers/use in your case.

The picture in the HFW review seems to show plastic pack output devices,
but I can't see well enough to determine the actual package type or size.
So am not sure of the likely power rating of the devices.

When an amp is designed to operate as class A, I wish the reviews and
producer info would specify details like this as it would indicate the
working limits.

It's worth noting that some manufacturers are less than honest about
this. Musical Fidelity in particular, whose '20 watt Class A' A1 amps
actually only ran up to *1 Watt* in Class A! To me, that's not even
rich-bias class AB..............

Even the mighty Krell were supposedly once guilty of this, as the
original KSA250 was rumoured to produce only 80 watts of true class A,
although this has always been disputed.
--

Stewart Pinkerton | Music is Art - Audio is Engineering