mick wrote:
On Wed, 17 Nov 2004 23:35:44 +0000, Ian Molton wrote:

snip

mick - if you wish to continue discussing this Im happy to respond to you.


Cheers, Ian.

Np. Im happy to natter when things are kept civil.

But our ears don't perceive an instrument as a point source. We hear
positional information

Nothing about a point source says it cant be somewher eother than
directly in front of you (although I had assumed that in my previous
example)

Even stereo point sources with perfect reproduction *may* be insufficient
to reproduce all the necessary information as much of it must be at very
low level

I dont think the level matters. But I agree that a stereo speaker setup
wont be able to reproduce a given scenario as it was originally, even in
a perfect room.

You are quite right - providing that the listener is comparing a point
source live instrument to an isolated single driver speaker in an anechoic
chamber. Another perfect microphone at the original listener's location
should give an exact copy of the source (although if you used a human
listener he/she should only have one ear, with the outer bit (pinnae? not
sure...) cut off!).

I think your logic is flawed there. the human wouldnt need to cut off
their outer ear.

I just have a hunch that the THD produced by a valve amp is doing more
than just giving a "warm" and "easy" feeling to the sound. I am wondering
if it is fooling the ear/brain combination in some way. That deception is
translated by some people into a feeling that the sound is more lifelike,
giving rise to their almost unanimous descriptions. This could be going
further than simple addition of even harmonics being used to "fill out"
musical sound to make it feel "bigger".

Its not *im*possible, but I dont think that adding information is
inherently better than simply accurately reproducing the original.

I don't know. Someone must have done, or be doing, research on this.

Probably.

Arny Krueger wrote:

No, the words "point source" are gratuitous, and an obvious attempt to
introduce either a straw man or a red herring.

Do try to think logically and do try to stay on topic.

To be fair, the point source was originally introduced by me.

"Patrick Turner" wrote in message
...


Mike Gilmour wrote:

"Patrick Turner" wrote in message
...

Expect thats the new bottles giving out the smell, had the same thing
happen here when I installed 8 new KT88's..the stink was 'orrible but
it
went away after about an hour. Funny that, because it's the first
time I
had quite that strong smell from new power valves...probably a bit of
burnt
bean sauce and rice wine after the factory lunch break :-) ......If
they
have one that is!

Mike

Smelly amps after turn on indicate the tubes have not even been tested
properly.


Yes that makes perfect sense. I'm in a habit of testing before use anyway &
giving power tubes a fairly easy start in life. I've generally found tube
suppliers to be fine exchanging defective or sub-standard bottles but I'm
not happy about the new possibility of premature tube death due to
improperly tested tubes..



I hope they last.
Chinese KT88 copies had a reputation for having a 40%
failure rate over 12 mths.

Dunno Patrick I went back to Svetlana's 6550C's again because I lost at
least 50% of the dynamics with the '88's but gained some (psudeo?) 'air',
IMO not worth the trade. Tried KT90's which went far too far in the
other
direction :-)

The problem is that chinese amps might look nice, even sound nice,
but the detailed examination of the circuit and output transformer
quality
often leaves a lot to be desired.

They seem to be improving slowly.

Get over there, you'd make a shed load of cash designing machines to make
wide band width OPT for future audiophile amplifiers

The designs for these have been common knowledge for 60 years at least,
and all the info on how is spelled out in RDH4.



Manley are very guarded about exactly how their recent OPT's are
manufactured. I guess though its just variations on a theme of RDH4 :-)


But the chinese like to make copies, and they overlook the inner details,
and some of the product is like a Rolex watch made in HK.


Fine 'til the gold turns green and the cockroach dies ;-)



Mechanised winders for transformers have been around for years,
and the asians don't need lessons or lectures from me.


Not the finer points of interleaving, bifilar etc. ;-)



The Zero was no match for a Huricane or Spitfire eh.


Ah - we've been there before Patrick...a long long thread, some time
ago.....


Patrick Turner.

. s ei




Patrick Turner.

The thd is less than 0.1% at up to 10 watts into any load between 4 and
12 ohms, which means that at 1 watt its down around 0.03%, even though
it is an SE amp.

That is quite good in itself. Does it maintain that into reactive loads, or
in 'intermod' situation where both LF and HF are present?

Its no worse than any other amplifier which is class A,
and which measures with such low thd.


I'd also be interested to know the (complex) o/p impedance as a function of
frequency and perhaps power level....

Ro = 0.5 ohms at 1 kHz, with about 7 uH inductance in series.
The leakage inductance in a tube amp is similar to the LR
zobel network fitted to the output of an SS amp to stop
the transistors ****ting themselves with a capacitive load.
But with the tube amp the leakage L is included in the FB loop, wheras the
L on the SS amp isn't, and many SS amps give a worse peaked
response into capacitive loads.

However, its rare that a pure C load is encountered; most ESL have some series
R in series with an equivalant amount of C, and a parallel R across the C,
and its enough to damp the peak in the response that would otherwise occur
at between 15 kHz and 35 kHz, depending on the C value.





[snip]

But an SS amp needs to have 10 times lower thd at the same levels of the
tube amp, say 0.003% because they mainly operate in the middle of the
switching region of the output transistors, and although the thd is low,

I note the "mainly" in your statement. :-)

Well, they do.

Many transitor amps have declining thd with output voltage,
and its difficult to see any thd in the signal at 3vo of output.

I recently built a tranny amp with ten MJL21193/94 devices per channel,
and after some effort, I got thd down to 0.01% at 157 watts,
mainly 3H, and then at 10 watts it was 0.004%, and little more than the thd in
my test signal,
and it fell towards zero as po was reduced.

But the thd was modulated by the rail swings from the mains jitter,
so the thd level changed dynamically..
Under normal conditions, class B amps have somewhat large swings
on their supply rails and these modulate all other frequencies.
Unless one regulates the rails or uses 100,000 uF caps, the thd is far worse
than what one
measures with a sine wave.

Class A tube amps have the advanatage ofr common mode rejection in the
CT OPT output stage.
SE class A tube designs have a continuous drain of power, and in any case huge
supply
caps are used, say 1,000 uF.

All class B amps which include nearly all SS amps used today
really need all the NFB they can muster because of the
nature of their intermodulation production.
Usually, because SS amps measure 10 times less thd than a tube amp,
they often cannot be distinguished from a decent tube amp which measures well
enough.
But I think the dynamic distortion mechanism within SS class B amps is 10 times

worse than the mainly class A tube amp, so the ten times greater NFB
amount leaves the two genres somewhat similar sounding to many people.
But not to all ppl, and some hear a lot more though a decent tube amp, and it
ain't got
much to do with measurements if the buyers of SET 300B amps are witnessed.

Regulated rails are one solution for class B amps.

But I have heard SS amps which ran from lead acid batteries,
and I heard nothing different.

Theives wouldn't ever steal that power supply!

Patrick Turner.

Arny Krueger wrote:

"Patrick Turner" wrote in message


Not all SS amps are plain crook, but enough are to give SS a bad name.

I liked you better Pat when you admitted that you abandoned making SS amps
because the competition was to hot and you couldn't make any money at it.

I didn't think you liked me at all.

But the competition is extremely hot for all electronics made outside asian
sweat shops.



One guy wanted to trade in his SS preamp full of oppamps for the tube
pre I had made after he had a listen.

Either the SS preamp was substandard trash, or he was being set up to take
an expensive fall.

Nothing conrived here.
The SS preamp was a respected Oz brandname.



I gently refused, because how would I sell this horror after folks
auditioned the tube pre?

...especially with you setting up the audition!

He chose levels and the discs, I merely witnessed
a tuberligious experience.

I don't sell amplifiers; they sell themselves.



He'd spent $3,000 on SS pre amd power amps, but after a year he could
stand it no longer, and went to all tubes, how's that for 22 yr old ears?

In many cases its all about preconditioning the listener.

I had absolutely nothing to do with what happened after he had a listen to some
real tube amps.

I didn't precondition anyone.

Patrick Turner.

In article , Ian Molton
wrote:
Kurt Hamster wrote:


The ears don't apply any distortion. YOu really don't understand
psycho-acoustics do you?

I wasnt talking about psychoacoustics. neither was micks only point
about psychoacoustics.

I can't comment on the psychology area, but the physiological processes in
the ear involve various forms of nonlinear response. However I'd say we
have to take care with calling this 'distortion' as it is probably better
considered as something like conversion or processing.

However IIUC your point correctly, Ian, it was that you were saying that
this happens in the hearing process, not in the sound as it is produced and
propagated. Hence if it is not externally applied when we listen to live
music, then it becomes debatable if we want equipment to apply a process
which our head will be performing anyway. (Thus applying it twice in
sucession, which would not occur for the live sounds.)

Snag being to try and equate or compare such 'external' and internal
processes, or make assumptions about what may do to the other. Not easy, as
we don't seem to really understand the implications of either process...

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

In article ,
Kurt Hamster wrote:
The brain damage occurred while you were drinking. Giving up doesn't
repair that damage.

What makes you think that?

The brain doesn't regenerate.

--
*If at first you don't succeed, redefine success.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Kurt Hamster wrote:
**Ah, so Keith WAS a drinker. That explains a great deal. The damage
has already been done.

And by his outburst about being teetotal, without qualification,
hopefully not in denial.

So you maintain that an alcholic can't become teatotal then?

No. Do you?

--
*How many roads must a man travel down before he admits he is lost?

Dave Plowman London SW
To e-mail, change noise into sound.

In article , Stewart
Pinkerton
wrote:


Could it be possible that non-linearity and the built-in distortion
factor is what causes the difference in sound?

Quite possible in some cases, I'd say. But hard to be sure.

That a perfect "wire with gain" amplification is actually *wrong* for
our ears simply because it does *not* introduce the distortion that
our hearing associates with "real" sound?

The difficulty here is that with live acoustic music we won't have such an
external nonlinear process interposed between the instruments and our
hearing physiology when listening to the music 'live'. However this depends
upon your definition of "wrong".

speculation mode = "on"
For example, it may be that some forms of 'distortion' alter the perception
by manipulating our physiology in a (not understood) manner. Thus altering
or 'enhancing' some aspects of listening to music. However for the reason
outlined above, is that live music with voices or acoustic instruments
won't be doing this, so we would not be getting this 'enhancement' with
such live music. Something like a valve amp for a guitar might do it, but
then if that is already being included at the recording stage, should more
of something similar be added later in the chain?...
/speculation mode



Hmm, interesting. (Very.)

No, it's not interesting at all. It's a very old and *very* misguided
argument. Certainly, our ears distort - but they distort in exactly the
same way when listening to the live performance as to a reproduction at
the same SPL.

I am wary here of the use of the term 'distort' as it implies using the
same word (and hence may imply to some people an equivalence in the
processes) for the nonlinear processes of human hearing physiology and the
nonlinearities of something like a valve amp. Hence this may be another
example of people risking getting into discussions based upon ambiguities
of language without noticing this is occuring. Using the same word may be
entirely understandable as a practice, but might be misleading.

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

In article , Andy Evans
wrote:
valves are outdated technology?


Well, while you guys have been arguing I just sold a pair of my valve
amps to drive Quad ELS 57s. So, soldering iron out and on to the next.

Hope you checked the stability... :-)

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