In article , Stewart
Pinkerton
wrote:

And Jim's research did indeed lead staright to what's wrong with the
Kraken - appalling current delivery! Into 4 ohms, it can only put out
the voltage equivalent of 18 watts into 8 ohms. You just *know* that's
going to be audible on peaks...........

OTOH, the effects decribed would be not unlike one of the classic
nonlinearities of valve amps, so that may be why you like it.

Well, the reports that I've now read from the URL that 'JustMe' gave seem
to contradict the HFW review in some respects, so the situation is not
entirely clear.

One 'nice' thing from my POV is that one of the other reviews comments to
the effect that the Kraken is designed to 'soft clip' so my guess on that
may be correct.

There are also - apparently - at least two versions of the Kraken, and
their behaviours may differ. One review (HFC) comments that the version
under test delivers more current (5.5A) than a previous version. They also
say they got a dynamic power of 90W into 4 Ohms.

The review in HFW (Sept 92) said the power was 50W/8Ohms but just
36W/4Ohms. However NK commented that this was distortion limited, so the
actual available power may be higher.

Taking the HFW values literally implies limits of 20Vrms (2.5Arms) into
8Ohms and 12Vrms (3Arms) into 4 Ohms if I calculate correctly.

The claimed 90W into 4 Ohms in the HFC review implies (assuming they mean
short-burst mean power) 18.9Vrms (4.7Arms). The 4.7Arms for a sinewave
implies a peak current of 6.7A which is above the 5.5A value they quote.

Taken at face value, the results seem inconsistent in detail, but make me
suspect two things:

1) That the amp and PSU can deliver higher currents and voltages for short
bursts than for sustained delivery.

2) That the o/p impedance may be 'high' - i.e. above 0.1 Ohms.

One report says the distortion level and frequency response alter as the
amp warms up. This may mean it is a low feedback design, which seems
consistent with (2).

Hence I suspect that this amp may be one that at times measures less well
with continuous sinewaves than it actually performs on music. Can't be sure
though, for the usual reasons - i.e. the reviews may simply contain errors
of fact, and certainly omit details that would tell us more.

BTW Afraid I found the website awkward to use. e.g. Data in large (6MB in
one case) PDFs that are essentially large bitmaps scans of the pages. Not a
very efficient way to provide a few pictures and some lines of text.
Interesting data, but I wish it had been provided as simple HTML, etc.
Took ages to download on my old dial-up connection. Then involved
manipulating 35MB+ bitmaps to read/print. :-/

He's a lecturer in electronics and physics at St Andrews University.
He's not filling in the exam paper, he's creating it.............

Yes, he knows what he's talking about.

My wife might disagree. Depends upon whether I'm agreeing with her, or
not... :-)

Slainte,

Jim

--
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Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html