Every amp in one
 

In article , Tat Chan
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

--
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

Every amp in one
 

In article , JustMe
wrote:

"Jim Lesurf" wrote in message
...
[snip]

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 Kraken itself is inside a half-width case, with an external
transformer in a case of its own.

Originally the Kraken was supplied with a single torriodal transformer
inside this case, with room for a second transformer, as a sonic
upgrade. Later models were supplied with the dual transformer PSU as
standard. Might these differences be the cause of the review
contradictions?

Yes, it might. Alas, this is one of the areas where the various reviews are
muddled. The HFW review claims that they tried both the single transformer
and double transformer PSUs and this (they said) had no effect on the
limited power into 4 Ohms. This is very odd if so. Hence their review may
simply be in error. However it is difficult to say without some more
reliable info. Unfortunately, plain errors of fact do occur in reviews.
[snip]


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.

Sorry about this. Most of the scans and specs are my own, which I try to
list as (still large) JPEGs. Because the site is an "archive", I've
tried to preserve the original source material and make that available,
rather then provide transcripts. To my mind, the originals reviews,
brochures and instruction manuals hold greater authenticity and are more
interesting artefacts.

I can certainly understand you wishing to ensure that material 'as close to
the original' is available. Unfortunately, this can make life difficult for
someone who has an old-fashioned dialup modem, etc - particularly when they
just want basic textual info plus a few images. For this, doing a few
webpages is much better in my opinion. Hence, ideally, you would have both.
However I can quite appreciate that you may not have time, or wish, to do
this. The material you have made available is welcome, and certainly *much*
better than if you had not done so. Your work is appreciated, despite my
"moan" above. :-)

The large PDFs you refer to are created from scans of the original
product brochures, which I believe are fairly rare. I don't believe that
these contain any further spec. not otherwise listed as text (laid out
in tables) on the product pages themselves.

OK. The problem was that I did not know this until after I downloaded the
pages and then viewed/printed them.

[snip]

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. :-/

Really? I'm not aware of any Kraken-related file larger than 4MB -
"kraken_mk2_brochure.pdf". Admittedly this is large, but it is a
separate "download" and not embedded onto any one page. I've just
checked and the entire site is 54MB, so am uncertain which file you are
referring to - please advise.

What you are referring to is the PDF file sizes, etc. However note that the
bitmaps in your PDFs are compressed by the PDF encoding. This is then
decompressed for viewing/use.

If you load the PDF files and view them, you are then looking at bitmap
images (the scans) of each page. Each of these bitmaps is over 30MB
uncompressed. Hence if you wish to manipulate the pages this becomes a
factor - although your OS and software may 'hide' this from your notice.
The snag is that other people may then encounter problems which are
invisible to you.

For example, people with older machines or software (who may not be able to
afford newer items) may sometimes run into problems.

In my case I do not normally use either Windows or Mac. Hence I have to use
'third party' software to view/print/manipulate PDFs. I was able to do this
OK, but rendering the large images took a wait per page as a result of the
way the software had to 'translate' the pages for rendering.

The PDFs are excellent for providing good-quality printed output. But they
are - in my view - less excellent for web and screen viewing for the above
reasons. FWIW for that I tend to prefer HTML with GIF/JPEG/PNG images.

However, regardless of the above, the info you have provided is certainly
welcome, and I am glad you have produced the files/pages for people to
access. I tend to be over-sensitised about the above issues as I use
non-Windows/Mac machines and have a history of producing 'educational'
sites where one of my concerns is "Will people in third world countries, or
who can't afford new kit be able to read this material?"

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

Every amp in one
 

In article , 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.

OK. That supports the idea that they are probably an excellent match for
the Kraken.

That said, I spent an hour this morning chopping down a large tree.
This was probably better for me than writing the exam. :-)

You know you're still a man if you can chop down a tree!

In that case it took me over 50 years to find out! ;-

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

Every amp in one
 

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

Every amp in one
 

"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?

Every amp in one
 

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?

Every amp in one
 

"Jim Lesurf" wrote in message
...
[snip]

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 Kraken itself is inside a half-width case, with an external
transformer in a case of its own.

Originally the Kraken was supplied with a single torriodal transformer
inside this case, with room for a second transformer, as a sonic
upgrade. Later models were supplied with the dual transformer PSU as
standard. Might these differences be the cause of the review
contradictions?

Yes, it might. Alas, this is one of the areas where the various reviews
are
muddled. The HFW review claims that they tried both the single transformer
and double transformer PSUs and this (they said) had no effect on the
limited power into 4 Ohms. This is very odd if so. Hence their review may
simply be in error. However it is difficult to say without some more
reliable info. Unfortunately, plain errors of fact do occur in reviews.
[snip]

Alchemist did specify that the additional PSU was a sonic upgrade and did
NOT increase power


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.

Sorry about this. Most of the scans and specs are my own, which I try to
list as (still large) JPEGs. Because the site is an "archive", I've
tried to preserve the original source material and make that available,
rather then provide transcripts. To my mind, the originals reviews,
brochures and instruction manuals hold greater authenticity and are more
interesting artefacts.

I can certainly understand you wishing to ensure that material 'as close
to
the original' is available. Unfortunately, this can make life difficult
for
someone who has an old-fashioned dialup modem, etc - particularly when
they
just want basic textual info plus a few images. For this, doing a few
webpages is much better in my opinion. Hence, ideally, you would have
both.
However I can quite appreciate that you may not have time, or wish, to do
this. The material you have made available is welcome, and certainly
*much*
better than if you had not done so. Your work is appreciated, despite my
"moan" above. :-)

Not at all - I take your point and urge you to seek broadband and, if not
available, to move into an area where such a facility is available :oP

The large PDFs you refer to are created from scans of the original
product brochures, which I believe are fairly rare. I don't believe that
these contain any further spec. not otherwise listed as text (laid out
in tables) on the product pages themselves.

OK. The problem was that I did not know this until after I downloaded the
pages and then viewed/printed them.

A good point - I will add file size info in the coming days/weeks.

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. :-/

Really? I'm not aware of any Kraken-related file larger than 4MB -
"kraken_mk2_brochure.pdf". Admittedly this is large, but it is a
separate "download" and not embedded onto any one page. I've just
checked and the entire site is 54MB, so am uncertain which file you are
referring to - please advise.

What you are referring to is the PDF file sizes, etc. However note that
the
bitmaps in your PDFs are compressed by the PDF encoding. This is then
decompressed for viewing/use.

If you load the PDF files and view them, you are then looking at bitmap
images (the scans) of each page. Each of these bitmaps is over 30MB
uncompressed. Hence if you wish to manipulate the pages this becomes a
factor - although your OS and software may 'hide' this from your notice.
The snag is that other people may then encounter problems which are
invisible to you.

For example, people with older machines or software (who may not be able
to
afford newer items) may sometimes run into problems.

In my case I do not normally use either Windows or Mac. Hence I have to
use
'third party' software to view/print/manipulate PDFs. I was able to do
this
OK, but rendering the large images took a wait per page as a result of the
way the software had to 'translate' the pages for rendering.

The PDFs are excellent for providing good-quality printed output. But they
are - in my view - less excellent for web and screen viewing for the above
reasons. FWIW for that I tend to prefer HTML with GIF/JPEG/PNG images.

Indeed - I though you were saying that the file size you were downloading
was 35MB, not that your computer itself was struggling with the file size.

Again I take your point, although I am unlikely to spend time on creating
duplicate pages for the forseeable future.

Most of my websites do not contain such large files anyway - the Alchemist
site is an exception, due to the nature of the material.

However, regardless of the above, the info you have provided is certainly
welcome, and I am glad you have produced the files/pages for people to
access. I tend to be over-sensitised about the above issues as I use
non-Windows/Mac machines and have a history of producing 'educational'
sites where one of my concerns is "Will people in third world countries,
or
who can't afford new kit be able to read this material?"

Right on!
I've found *nix users tend to be sensitive about such issues :o)

Slainte,

Jim

Every amp in one
 

In article , JustMe
wrote:
Jim Lesurf wrote:


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


Surely you have learned more *to* forget?


Well, if I could remember, I could answer the above question... :-)

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

Every amp in one
 

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


The HFW review claims that they tried both the single transformer and
double transformer PSUs and this (they said) had no effect on the
limited power into 4 Ohms. This is very odd if so. Hence their review
may simply be in error. However it is difficult to say without some
more reliable info. Unfortunately, plain errors of fact do occur in
reviews. [snip]

Alchemist did specify that the additional PSU was a sonic upgrade and
did NOT increase power

That is quite curious. It implies they are concerned with 'crosstalk', but
not with the peak/mean powers available. If what you say is correct it
implies a deliberate design as otherwise doubling the PSU would tend to
change the available power. Seems odd to specifically prevent this. Did
they give a reason for deciding to prevent the dual PSU from providing more
power?

It makes it sound like either they had a quite specific (unstated) 'sonic'
reason for preserving the clipping/limiting behaviour, *or* that they were
concerned about the IV safe operating areas of the o/p devices.

[snip comments on file size]

Not at all - I take your point and urge you to seek broadband and, if
not available, to move into an area where such a facility is available
:oP

:-) I don't normally download/upload much per day, and prefer to keep my
total costs down. Hence I have avoided broadband thus far. I'm afraid that
I like where I live too much to consider moving for something like this.
:-)

[snip]


However, regardless of the above, the info you have provided is
certainly welcome, and I am glad you have produced the files/pages for
people to access. I tend to be over-sensitised about the above issues
as I use non-Windows/Mac machines and have a history of producing
'educational' sites where one of my concerns is "Will people in third
world countries,
or
who can't afford new kit be able to read this material?"

Right on! I've found *nix users tend to be sensitive about such issues
:o)

FWIW I don't use Linux, either. :-)

I *do* use Solaris (UNIX) a bit, but mostly use RO for day-to-day deskwork.
My main concern, though, was that it took about 15-20mins to fetch a
(6MB) PDF. This isn't an OS issue, but affects those who either choose
to use an 'old fashioned' dialup - or who have no choice. As you say,
though, using systems that aren't what most people are familiar with
does tend to bring more awareness of these issues.

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

Every amp in one
 

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