On Thu, 21 Oct 2004 20:17:46 +0300, "Iain M Churches"
wrote:



"Jim Lesurf" wrote in message
...
You can, of course, say the same about many individual technical specs
taken in isolation. Ideally, the amp should be 'adequate' or better on the
basis of a series of specs. This, in my experience thens to be what
mathematicians call "necessary but not sufficient" as a guide. i.e. if you
fail some specs you can expect the sound to be altered in predictable
ways.

In article , Iain M Churches
wrote:

As regards distortion, I have found that the amount of THD is not so
important as the distortion content - the way the THD is made up. For
example amplifiers with a small amount of 3rd harmonic sound less
pleasing than amplifiers with a larger amount of 2nd harmonic.

I have found that amplifiers with the most pleasing (this may not be the most
accurate:-) sound seem to have a harmonic distortion decreasing gradually as
the order increases. This is perhaps one of the problems with NFB. It cancels
the "benign" even harmonics, leaves exposed the more unpleasant odd
harmonics.

Utter bull****! NFB affects all frequencies equally - within the
limits of open-loop gain.

However my personal preference is for amplifiers that have minimal levels
of distortions at whever harmonics fall in band.

Cant argue with that! :-)

I have listen extensively to large Crown (Amcron) and Carver broadcast amps.
They have incrediblt low distortion figs which as a builder of valve amps I can
only dream of. They may be incredibly accurate, but their sound leaves me
cold.

So, you prefer the *added* artifacts of valve amps. Fine for you, but
what has this to do with fidelity to the source signal?

I agree entirely. It may also be that on the test bench
we put too much importance on some
measurements and do not undestand the relevance of others. In valve
amplifiers for example damping factor has an enormous bearing on the way
the amplifier sounds.

Only because it tends to be pathetically inadequate...............

One takes a high DF for granted in an SS amp. In
a valve amplifier, a figure above twenty (which seems adequate in listening
tests) is not easy to achieve.

So why bother with valve amps? Unless of course you have a
*preference* for added colouration................
--

Stewart Pinkerton | Music is Art - Audio is Engineering

In article , Iain M Churches
wrote:


"Jim Lesurf" wrote in message
...


I have found that amplifiers with the most pleasing (this may not be the
most accurate:-) sound seem to have a harmonic distortion decreasing
gradually as the order increases.

That may be your experience. However my personal interest is not actually
in amplifiers with a 'pleasing sound'. I don't want the amp to have any
noticable distortion signature. I'm trying to listen to the music without
it being affected by an amplifier 'sound'.


This is perhaps one of the problems with NFB. It cancels the "benign"
even harmonics, leaves exposed the more unpleasant odd harmonics.

I've seen comments like that made many times. However feedback should
reduce nonlinearity. Not sure why NFB should be assumed to act more on
'even' than 'odd' harmonics.

Again, TBH, I am more concerned with intermodulation or distortions that
create anharmonic components as these have seemed to me to be much more
noticable at a given level than simple harmonic distortion. However to get
low IMD tends to imply we'd get low harmonic distortion as well...


However my personal preference is for amplifiers that have minimal
levels of distortions at whever harmonics fall in band.

I have listen extensively to large Crown (Amcron) and Carver broadcast
amps. They have incrediblt low distortion figs which as a builder of
valve amps I can only dream of. They may be incredibly accurate, but
their sound leaves me cold.

Can't comment as I have no idea why you would feel that from what you say.
Hence I could only make guesses.

My main interest is in high quality valve amplifiers, which IMO are
much more of a challenge for a designer than SS (I also happen to
like the way valve amplifier can sound)

Depends what you mean. :-)

I am fortunate enough to be a recording engineer by profession, so I
have for many years had the opprtunity on classical sessions to sit in
the studio during rehearsals and hear the "real" sound, which can then
be used as a reference for what is coming out of the loudspeakers. Even
in this digital age of hard disc multitrack systems, I still use a
Radford STA100 .(UK built 1964) for monitoring.

I was fortunate enough to be employed as an audio designer for some years,
which made me feel like a "kid in a sweetshop" at the time. :-)

My recollection is that Radford made some good valve amps. In particular,
they paid an unusual amount of attention to measuring, analysing, and
designing around the area of phase control, transformer behaviour, and
ensuring good stabilty margins. Alas, my impression is that since then many
of the 'home brew' valve amps people make do not benefit from this.


Yes. The difficulty, though, is ensuring you make the relevant
measurements and can interpret the results appropriately. One of my
niggles with audio reviews is that they often fail to do this and just
give simple standard values that don't tell us much.

I agree entirely. It may also be that on the test bench we put too much
importance on some measurements and do not undestand the relevance of
others. In valve amplifiers for example damping factor has an enormous
bearing on the way the amplifier sounds. One takes a high DF for
granted in an SS amp. In a valve amplifier, a figure above twenty
(which seems adequate in listening tests) is not easy to achieve.

I would certainly agree with the above. This is one of the reasons I am
less than happy with many of the reviews in magazines. People have known
for decades that the output impedance can affect the performance in audible
ways - and that this will vary with the speaker as well. Hence to omit any
consideration of this from valve amp reviews strikes me as 'uninformative'.

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

"Andy Evans" wrote in message

Contrary to what Stewart and others think, I've spent 35 years
building and tweaking hifi with one aim in mind - to make the hi-fi
system sound like live music. I didn't use measurements for this, I
used my ears since I've been a professional musician for most of my
life. I also did all improvements methodically, switching one thing
at a time, and preferring a closer approach to the original sound,
more fidelity in instrumental timbre and more detail, reasoning that
any unrealistic timbre or detail masked was not 'fidelity' to the
source.

Ignorance of the need for level matching and blind testing for many of these
comparisons, noted.

OK. ~ Now the point is this: How many of us know exactly how
acoustic instruments and voices actually sound?

Yup, all acoustical instruments of a kind sound the same, regardless of who
plays them, where you play them or where you are standing with regard to the
instrument when it is played.

If one allows that the sound of a given kind of musical instrument varies
with the brand, model and even sample, that different players make them
sound different, that they sound different in different rooms and when you
are in various locations w/r/t the instrument then you come up with a simple
answer:

Virtually nobody ever knows a priori how the instrument sounds.

If you go to live
classical or jazz concerts where music is unamplified (plus folk
etc), it actually has a particular sound to it which is smooth,
natural, even bland.

Unless the particular circumstances make it sound otherwise...

It's unimpressive in many ways compared to our
"delusional" hifi kits and our delusional hifi language. It doesn't
have 'warmth', or 'bloom' or 'bass slam' or even PRAT. What it does
have is a lot of nothing - nothing between individual instruments
except space.

Except when it doesn't.

To reproduce this it's necessary to reproduce a lot of
nothing, which is the fantastically difficult bit. It means no gloss
on the treble, no large soundstage to instruments - they should sound
like small point sources in exact locations in the soundstage - no
'dynamics' that aren't actually there, and no 'bass slam'. Pretty
boring you might say. And very hard to achieve - you have to
eliminate resonances, all sorts of interferences etc etc. You don't
so much 'build' a syetem but 'take away' infidelities of all kinds.

However, the infidelities are always non-zero.

At this point Stewart must be rubbing his hands and saying "I told
you so - acoustically transparent". Jim must be happy that the
amplifier doesn't exist. It all sounds great.


Except that this isn't
the gospel according to Stewart. Because: a) I'm quite sure
amplifiers and indeed componants sound different, and I've been doing
systematic choices between componants to eliminate infidelities for
countless years.

IOW it's gotta be true because you've believed the same thing for years.
Wow, that must be a scientific theorum, right?

b) I've done all this by ear

No, by eye, ear, unmatched levels, not time-synched, etc.

c) I use all valve equipment,

Bragging or complaining?

and I don't think I could get transparency so easily with solid state.

IOW it's gotta be true because you've believed the same thing for years and
years. True science strikes again.

d) I don't think valves sound 'warm' - another delusion

Bragging or complaining?

- the ones I build sound smooth (to my ears smoother than solid
state) and dynamic (without a kind of 'greyness' I hear in some solid
state products)

definately bragging.

e) I don't think there is such a thing as
'acoustically transparent', only approximations towards this goal.


IOW it's gotta be true because you've believed the same thing for years and
years and years. Where is science when you need it?

Why this post then? I just eliminated another level of grunge - yes,
more has "gone" leaving the sound a lot better. I started by using
better speaker cables (solid copper core, the previous ones were
coloured).

More opinion stated as fact.

Then I wired my whole system through a monster variac
which I have (25 amps). Obviously an effective mains cleaner.


Not so obviously an effective mains cleaner, since some Variacs have
nonlinear cores.

Some
studios use huge toroids for this, like over 1K VA isolation
transformers, e.g. mine is over a foot in diameter and 6" high.

I got one just like that, but I use it for bringing up SS amps under test.
Saves a lot of fried parts.

My
first reaction was that the sound was boring. The "foreground" of the
sound was less obvious - the soundstage was the same, neither more
forward or backward, but instruments sounded relatively tiny and
melodies less 'obvious'. There was a lot of nothing between
instruments, and their actual location was spookily exact. The sound
seemed quieter because of this, and also the treble seemed dim
initially. In fact the treble was all there, and the sound of the
triangle and cymbals was exactly right, just not spread all over the
place. It took a while for it to dawn on me that this was the closest
I had come to the sound of live music. Yep, smooth, quite bland, a
lot of nothing but loads of fine detail, faithful timbre to
instruments - in short a step further towards acoustically
transparent. No warmth, no bloom, no PRAT, no bass slam. Spooky.

Probably delusional.

After a little while I started to get excited! And looking back on
the whole saga of 'warm valve amps', PRAT, slam etc etc, the whole
business of Hi-Fi seemed delusional. I'm sure this post will be of
little use to those who listen mainly to rock and amplified music,
but for those who listen to classical and acoustic music, getting
closer to 'nothing much except the live sound of music' may matter a
lot. It's taken me 35 years to eliminate enough grunge to actually
get this far, and no I couldn't have got there sooner or even at all
with a big Krell - I know that one very well, my brother has a Krell
and Apogees, and I've heard all manner of big ss amps in high end
demos. I'm quite unrepentant about how I've made my Hi-fi sound
natural, and all the changes I've done have been carefully thought
out. It's a bit like Salome's seven veils - you have to lift all the
veils to see what's really there, which is, errm, nothing. Thought
for the day.

This round of self congratuation was brought to you by Andy Evans.

As a matter of interest, Arny, which of these describes you?
a) I spend most of my time helping people
b) I divide my time between helpig people and mocking people
c) I spend most of my time mocking people

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

"Andy Evans" wrote in message


As a matter of interest, Arny, which of these describes you?
a) I spend most of my time helping people
b) I divide my time between helpig people and mocking people
c) I spend most of my time mocking people

(a), with a bullet!

However, some of the ways one helps people may involve using some humor.

On Tue, 19 Oct 2004 12:14:21 -0400, "Arny Krueger"
wrote:

"Andy Evans" wrote in message


As a matter of interest, Arny, which of these describes you?
a) I spend most of my time helping people
b) I divide my time between helpig people and mocking people
c) I spend most of my time mocking people

(a), with a bullet!

In my all too long experience of your posts, not so. Your website is
extremely useful to those with more than three braincells to rub
together, but your posts are definitely (c). And done with no
perceptible wit or humour.
--

Stewart Pinkerton | Music is Art - Audio is Engineering