"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.

On Fri, 26 Nov 2004 02:33:51 -0000, "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.

Anything that runs *that* hot, had damn well better have lots of bias
by deliberate intent!
--

Stewart Pinkerton | Music is Art - Audio is Engineering

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.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

"Jim Lesurf" wrote in message
...
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.

Slainte,

Jim

Pics of the actual amps I'm using (including internals) are at the same URL
I gave previously, or via
http://www.alchemisthifi.info/ranges...aken_index.htm
If by "plastic pack" you mean they come in strips in plastic packaging, then
that rings true with what I've seen of op devices used in other Alchemist
amps.
What significance would this hold?

In article , JustMe
wrote:
"Jim Lesurf" wrote in message


Pics of the actual amps I'm using (including internals) are at the same
URL I gave previously, or via
http://www.alchemisthifi.info/ranges...aken_index.htm If by
"plastic pack" you mean they come in strips in plastic packaging, then
that rings true with what I've seen of op devices used in other
Alchemist amps. What significance would this hold?

Being able to identify the pack tells us the probably max power ratings of
the devices and the thermal conductivity between the active devices and the
heatsink. This then has implications for what current*voltage levels are
'safe' for normal operation. For simple class A, this then may indicate the
current and voltage chosen by the designer, and the implied maxium levels
available in class A. Thus can do some 'guesstimates' of these things
without actually looking up the device number. The complication is that the
safe power 'derates' with the temperature, so a good pack and heatsink
allow you to get higher powers from the same actual semiconductor device.

Given the comment you make elsewhere about the dual PSU *not* increasing
the power I am wondering if the peak current and voltage are being
deliberately limited for thermal and safety reasons. (Safe here means the
devices continue to work OK.)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

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