Opinion needed re power amp building
 

"Jim Lesurf" wrote in message
...
In article , Trevor Wilson
wrote:

"Jim Lesurf" wrote in message
...
In article , Trevor Wilson


So the person throwing the switch did know which choice (A or B) they
had made at each time?

**They knew whether it was A or B, but not which amp was which.

That means the result isn't double-blind. The point of
double blind is that *noone* involved in either running or taking the
test has *any* idea which - A or B - is being presented at the time.

**True enough. I never claimed that the test was perfect.

But the above means that the test can't be established as blind.

**Like I said: It was not a perfect test.

So the
results could easily be for reasons other than the one you asserted. i.e.
nothing to do with 'MOSFET' being any different to 'Bipolar' as classes of
o/p device. Thus your evidence isn't reliable as a basis for your belief.

**It is not a belief. The test was constructed in an attempt to verify what
I and others had already informally noted as having heard.



Where was the 'switch'?

**In different room to the speakers systems being listened to.

No. I meant where in the experimental system?

**At the speaker terminals of the amplifiers. The switches were relays.



, how were they recruited, how much did they know about the
purpose of the test? etc.

**They only knew that there might be a change in the system when the
light changed from green to red.

Which "light" controlled how?

**The light in the listening room.

Controlled *how*?

**By the person throwing the switch. He also controlled the lights. The
lights merely indicated a POSSIBLE change in amplifier.


Raw data of results?

**Lost in the mists of time. The results were 100% anyway.

That has no assessable meaning without knowing how many times the test was
done, if the same material was used, conditions of tests, etc, etc.

**I understand and have acknowledged the imperfect nature of the test.


Statistical analysis and outcomes in terms of levels
of confidence, etc?

**The participants picked which amp was playing 100% of the time.

Problems as above.

I could easily say "I spent 2 mins listening to one amp, then 1 min
listening to another. I could hear they were different. 100% right." Alas,
as evidence that would be worthless.

**Indeed. Except that the listeners were able to correctly identify each
amplifier perfectly.


Are you not aware of the various proceedural and other flaws that can
spoil
a test even when 'blind'? e.g. the flaws with the Stereophile tests they
did at a show some years ago?

**I am now, but was not then. If I were to perform a similar test today, I
would certainly be doing things very differently.



Which 'amps' did you try?

**Phase Linear 400(b) and Perreaux 2150.

What were the details of the level matching,
avoidance of clipping/saturation etc?

**I installed level pots in each amp and matched levels to within 0.1dB
or better. Prior to the testing, I used my CRO (Tek 465b) to ensure
that the amps never reached Voltage limiting with the music used for
the test. The main volume control was marked with a line and
instructions that it always remain below that line (Voltage limiting).
In my prior testing, I found that normal listening levels rarely
exceeded 15 - 16 Volts RMS.

How did you establish that *current* limiting never occurred?

**I didn't. In fact, when using the Quad ESL63 speakers (I also used KEF
104.2 speakers), I suspect that both amps would have experienced current
limiting at some point.

My experience
with o/p fets from days of yore is that they were far more prone to this
than bipolars.

**Indeed. However, the current limiting of MOSFETs has always tended to be
more benign than BJTs (depending on how the BJT current limiting is
employed).


How did you monitor for any current limiting or clipping *during the
tests*?

**No. As I previously stated though, I checked the music, prior to the test
with my CRO and did not note any significant issues. Yes, I am well aware of
how transient the nature of current limiting can be and, thus how current
limiting could have occured.

The problem here is that real-world speakers can be more demanding
of current that you might be aware when playing music.

**Indeed. OTOH, the KEFs were chosen for a couple of reasons. One is the
extensive use of Zobels throughout the crossover and the consequently
relatively smooth 4 Ohm load presented. The ESL63 was not as easy to drive.
In fact, the differences between the two amps was far more profound with the
Quads, than with the KEFs.



How did you establish the results *were* a basis for conclusions about
one form of transistor versus another rather than being a problem with
some specific designs or devices?

**I didn't, though I've noted (informally) that most (all?) Class A/B
MOSFET amps exhibit similar sonic issues to those I heard several
decades ago.

Afraid that is an opinion, not assessable evidence.

**Indeed. Hence the inclusion of the word: "informally".



Given all the work, where did you publish the results?

**It was for me and to prove a point to some of my sceptical clients. As
you have already discovered, the test was hardly rigorous enough to
publish.

Since your results
seem to run contrary to all the published results I've seen

**Do they? Can you cite where a DBT was performed using a Phase Linear
vs. a Perreaux?

Sorry. I thought you were claiming that *MOSFETS* sounded different as a
class of device to *Bipolars*. Are you now *only* saying that the Phase
Linear sounded different to 'a Perraux'?

**Nope. Those are the two amps I tested. I have not performed any tests
since. All listening has been done on a much more informal basis.


So are you making no claim wrt this being a general result for the two
types of output device regardless of the choice of individual device type
or circuitry?

**The measured performance of both amplifiers significantly exceeded the
limits of human hearing WRT frequency response, THD, IMD et al. Both amps
had roughly similar power output capability. Certainly, the topology of both
amps is somewhat different, but the big differences lie in the use of
different technology output devices.



- and I suspect
would have been welcomed by many 'subjective reviewers' I would expect
them to have been eager to have them published.

**Subjective reviewers tend to avoid DBTs.

I wonder why? :-)


The problem is that you've only now given us your selected
recollections. Not the evidence anyone else would need to see if what
you say stands up as a conclusion.

**Indeed. Perhaps you may care to relicate my test?

You are offering to send me a Phase Linear and 'a Perraux' so I can do
this
with no costs to myself?

**Nope. Both amps are common and cheap.


If so, then I still would have some problems. One is that I can't
'replication your test' because you haven't actually defined all that was
involved and given me your raw data, etc so I could see if I could either
match what you did, or spot any flaws that would make a repeat pointless.
If I did the test differently, then I might not replicate your results for
that (unknown) reason.

**Fair enough.


Or are you asking me to (again) compare different amps using a better
defined method which might differ from the one you used?

**That would be a possibility. If you feel that it might be constructive to
do so.



If the latter, it is something I have done many times in past decades. The
results in general were that neither I - nor others I tried them on -
could
relaibly tell one amp from another. i.e. they/I showed no ability to do so
with statistical reliability.

**You have directly compared Class A/B MOSFET amps with Class A/B BJT amps?


Only exceptions were when there was a measureable difference like one amp
was clipping/saturating or the gain levels or frequency response were
sufficiently different.

**Sure.


Yes, I did experiment with MOSFET amps. I found they worked OK provided
you
could ensure the circuit drove them without allowing RF bursts, and you
kept within their limited current range. I preferred bipolars because I
personally found them easy to use, and they could provide large peak
currents, etc. So seemed to me more suited to real music.

**Indeed. In the early days, BJTs provided significantly more current for
much less money. Not so much today. MOSFETs capable of delivery large
currents are relatively cheap.


And I'm afraid that these days I don't think it would be fair to do such a
test simply using my own ears. Afraid I am now too old for that to be
reliable. So I'd need to line up a set of listeners generally younger and
more alert than myself. Would you be paying for any of this?

**Not a chance. If you are sufficiently motivated you will do what I did. If
you are not, then you won't.


--
Trevor Wilson
www.rageaudio.com.au

Opinion needed re power amp building
 

In article , Trevor Wilson
wrote:

"Jim Lesurf" wrote in message
...
In article , Trevor Wilson
wrote:

"Jim Lesurf" wrote in message
...
In article , Trevor Wilson


So the person throwing the switch did know which choice (A or B)
they had made at each time?

**They knew whether it was A or B, but not which amp was which.

That means the result isn't double-blind. The point of
double blind is that *noone* involved in either running or taking
the test has *any* idea which - A or B - is being presented at the
time.

**True enough. I never claimed that the test was perfect.

But the above means that the test can't be established as blind.

**Like I said: It was not a perfect test.

That does seem rather an understatement. Given that your answers indicate
that the test may well have been worthless, certainly so as evidence for a
claim that - as a class of devices - MOSFETs and BJTs 'sound different'.



So the
results could easily be for reasons other than the one you asserted.
i.e. nothing to do with 'MOSFET' being any different to 'Bipolar' as
classes of o/p device. Thus your evidence isn't reliable as a basis
for your belief.

**It is not a belief.

I'm afraid that simply re-asserting a belief does not make that belief
correct as a description of reality.

The test was constructed in an attempt to verify
what I and others had already informally noted as having heard.

But from your own answers since, clearly cannot have done that if what you
wished to verify was if MOSFETs and BJTs sounded different as a class of
devices. So by your own comments since, the test results were worthless for
that purpose.


, how were they recruited, how much did they know about the
purpose of the test? etc.

**They only knew that there might be a change in the system when
the light changed from green to red.

Which "light" controlled how?

**The light in the listening room.

Controlled *how*?

**By the person throwing the switch. He also controlled the lights. The
lights merely indicated a POSSIBLE change in amplifier.

So they also operated this light as often when there was no change as when
there was? To have not done so would be a methodological flaw unless you
dealt with established 'difference' bias in some other way. cf the
Stereophile test that fell foul of this problem and thus produced a false
claim about amps being shown to sound different.


Raw data of results?

**Lost in the mists of time. The results were 100% anyway.

That has no assessable meaning without knowing how many times the test
was done, if the same material was used, conditions of tests, etc, etc.

**I understand and have acknowledged the imperfect nature of the test.

But not that the results are actually of no worth in supporting the view
you initially expressed re MOSFET versus BJT.



Statistical analysis and outcomes in terms of levels
of confidence, etc?

**The participants picked which amp was playing 100% of the time.

Problems as above.

I could easily say "I spent 2 mins listening to one amp, then 1 min
listening to another. I could hear they were different. 100% right."
Alas, as evidence that would be worthless.

**Indeed. Except that the listeners were able to correctly identify each
amplifier perfectly.

Which is meanignless in this case for the purposes of your initial claim.


How did you establish that *current* limiting never occurred?

**I didn't. In fact, when using the Quad ESL63 speakers (I also used KEF
104.2 speakers), I suspect that both amps would have experienced
current limiting at some point.

In that case any difference could quite easily come from differences in the
current limiting behaviours of the two specific designs using the specific
devices. Nothing to do with MOSFET versus BJT as a class of device.

My experience
with o/p fets from days of yore is that they were far more prone to
this than bipolars.

**Indeed. However, the current limiting of MOSFETs has always tended to
be more benign than BJTs (depending on how the BJT current limiting is
employed).

That depends on how you define 'benign'. I define it as being 'never
happens in the normal use because the saturation level is above the peak
demanded'. You may be defining it to mean 'don't blow up the amplifier'.
But I take that as a safety requirement. :-)

In the above context I regard BJT behaviour as more 'benign' for music as
the devices tend to allow very high peak currents *without* saturation or
failure. Whereas FETs tend to dumbly limit at a specified level, for peaks
or for continuous. That is OK for test sinewaves, but not ideal for music.


How did you monitor for any current limiting or clipping *during the
tests*?

**No. As I previously stated though, I checked the music, prior to the
test with my CRO and did not note any significant issues. Yes, I am
well aware of how transient the nature of current limiting can be and,
thus how current limiting could have occured.

Thus meaning your test can't support the original claim you made.

The problem here is that real-world speakers can be more demanding
of current that you might be aware when playing music.

**Indeed. OTOH, the KEFs were chosen for a couple of reasons. One is the
extensive use of Zobels throughout the crossover and the consequently
relatively smooth 4 Ohm load presented. The ESL63 was not as easy to
drive. In fact, the differences between the two amps was far more
profound with the Quads, than with the KEFs.

If so, that supports what I am saying.



How did you establish the results *were* a basis for conclusions
about one form of transistor versus another rather than being a
problem with some specific designs or devices?

**I didn't, though I've noted (informally) that most (all?) Class A/B
MOSFET amps exhibit similar sonic issues to those I heard several
decades ago.

Afraid that is an opinion, not assessable evidence.

**Indeed. Hence the inclusion of the word: "informally".

And means you can't then quote the results to try and use them to support
your beliefs when making claims about them to other people. As you seem to
have been doing... :-)



Given all the work, where did you publish the results?

**It was for me and to prove a point to some of my sceptical clients.
As you have already discovered, the test was hardly rigorous enough
to publish.

Since your results
seem to run contrary to all the published results I've seen

**Do they? Can you cite where a DBT was performed using a Phase
Linear vs. a Perreaux?

Sorry. I thought you were claiming that *MOSFETS* sounded different as
a class of device to *Bipolars*. Are you now *only* saying that the
Phase Linear sounded different to 'a Perraux'?

**Nope. Those are the two amps I tested. I have not performed any tests
since. All listening has been done on a much more informal basis.

So your claim now is simply about those two amps? Any previous statements
you made should not now be taken to mean you are claiming that MOSFETs
sound any different to BJTs as classes of device?


**Indeed. Perhaps you may care to relicate my test?

You are offering to send me a Phase Linear and 'a Perraux' so I can do
this with no costs to myself?

**Nope. Both amps are common and cheap.

Which should make it cheap and easy for you to obtain them for me.

Afraid I can't recall the last time I saw either amp. Indeed the name
'Perraux' does not mean anything to me as I can't recall an amp of that
name at present.

If they are so cheap, would you pay the price if I found one of each amp
and told you the asking prices? You are probably safe here as I suspect
no-one in the UK will have both amps for sale at any price!




If the latter, it is something I have done many times in past decades.
The results in general were that neither I - nor others I tried them
on - could relaibly tell one amp from another. i.e. they/I showed no
ability to do so with statistical reliability.

**You have directly compared Class A/B MOSFET amps with Class A/B BJT
amps?

Yes. I repreatedly did that in the past. Remember I was involved in
developing a new amp back in the late 1970s and early 1980s. As part of
that I both 'borrowed' a range of designs from others and built a number of
them myself. Then tested them in listening comparisons as well as on a test
bench. At that time Hitachi and others were bringing in their new FET
designs.

During the late 1980s and into the 1990s I also did some similar things
with a few friends, one of whom is actually a very good amp designer in my
view.

The results were as I have said. That provided we avoided simply and
obvious problems like level mismatch, gross distortions, ensured stability,
avoided clipping or saturation, etc, the amps gave no reliable sign of
producing audible differences.

But then we were careful to allow for the way many other factors can affect
perception. So avoided trying to jump to conclusions.

And as I have said, all the well-performed comparisons I've seen reported
come to the same conclusion.

Some reports initially concluded otherwise - e.g, the Stereophile test. But
when examined the results turn out not to reliably do what was initially
believed.


And I'm afraid that these days I don't think it would be fair to do
such a test simply using my own ears. Afraid I am now too old for that
to be reliable. So I'd need to line up a set of listeners generally
younger and more alert than myself. Would you be paying for any of
this?

**Not a chance. If you are sufficiently motivated you will do what I
did. If you are not, then you won't.

I see no reason to bother at the moment since you haven't actually provided
any evidence that you *did* hear a difference due to MOSFET versus BJT as a
class of device. Instead you may simply have found that currently limiting
can be audible. Which does not surprise me as it agrees with my own
experience and would be so for perfectly understandable reasons. :-)

But if you can find an ultra-cheap pair of the amps you used and are
willing to buy them, I'd enjoy trying them. If only to measure the current
limiting behaviours. :-)

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Opinion needed re power amp building
 

Jim Lesurf wrote:

In article , Trevor Wilson
wrote:

[snip - Phase Linear v Preeeaux]

**Nope. Both amps are common and cheap.

Which should make it cheap and easy for you to obtain them for me.

Afraid I can't recall the last time I saw either amp. Indeed the name
'Perraux' does not mean anything to me as I can't recall an amp of that
name at present.

http://www.perreaux.com in New Zealand. Expensive!!

http://uk.cinenow.com/articles/9440-...ntergrated-amp

--
David Pitt
Snow Leopard - MessengerPro

Opinion needed re power amp building
 

In article , David Pitt
wrote:
Jim Lesurf wrote:

In article , Trevor Wilson
wrote:

[snip - Phase Linear v Preeeaux]

**Nope. Both amps are common and cheap.

Which should make it cheap and easy for you to obtain them for me.

Afraid I can't recall the last time I saw either amp. Indeed the name
'Perraux' does not mean anything to me as I can't recall an amp of
that name at present.

http://www.perreaux.com in New Zealand. Expensive!!

So despite what Trevor said, neither common (I can't recall ever
encountering one in the UK) nor cheap.

Oh well, if Trevor wants to buy me one for Xmas I can then give it a listen
and see if it justifies his claim that it isn't worth using. :-)

Slainte,

Jim

http://uk.cinenow.com/articles/9440-...ntergrated-amp

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Opinion needed re power amp building
 

Jim Lesurf wrote:

In article , David Pitt
wrote:
Jim Lesurf wrote:

In article , Trevor Wilson
wrote:

[snip - Phase Linear v Perreaux]

**Nope. Both amps are common and cheap.

Which should make it cheap and easy for you to obtain them for me.

Afraid I can't recall the last time I saw either amp. Indeed the name
'Perraux' does not mean anything to me as I can't recall an amp of
that name at present.

http://www.perreaux.com in New Zealand. Expensive!!

So despite what Trevor said, neither common (I can't recall ever
encountering one in the UK) nor cheap.

Perreaux kit may be cheap and common in Australia, where Trevor is. From the
Perreaux site the éloquence range, which uses MOSFET output devices, give an
output that is "dynamic, commanding and resolute". Trevor would disagree
with that first term.


--
David Pitt
Snow Leopard - MessengerPro

Opinion needed re power amp building
 

On Sat, 7 Nov 2009 10:28:31 +0000, David Pitt
wrote:

Jim Lesurf wrote:

In article , David Pitt
wrote:
Jim Lesurf wrote:

In article , Trevor Wilson
wrote:

[snip - Phase Linear v Perreaux]

**Nope. Both amps are common and cheap.

Which should make it cheap and easy for you to obtain them for me.

Afraid I can't recall the last time I saw either amp. Indeed the name
'Perraux' does not mean anything to me as I can't recall an amp of
that name at present.

http://www.perreaux.com in New Zealand. Expensive!!

So despite what Trevor said, neither common (I can't recall ever
encountering one in the UK) nor cheap.

Perreaux kit may be cheap and common in Australia, where Trevor is. From the
Perreaux site the éloquence range, which uses MOSFET output devices, give an
output that is "dynamic, commanding and resolute". Trevor would disagree
with that first term.

I have no idea what any of those terms means as applied to an
amplifier. Clues anybody?

d

Opinion needed re power amp building
 

Opinion needed re power amp building
 

On Sat, 7 Nov 2009 10:58:23 +0000, David Pitt
wrote:

(Don Pearce) wrote:

On Sat, 7 Nov 2009 10:28:31 +0000, David Pitt wrote:

[snip]

Perreaux kit may be cheap and common in Australia, where Trevor is. From
the Perreaux site the éloquence range, which uses MOSFET output devices,
give an output that is "dynamic, commanding and resolute". Trevor would
disagree with that first term.

I have no idea what any of those terms means as applied to an amplifier.
Clues anybody?

They don't mean anything, in my view, as applied to an amplifier, they are
of no help at all. That is one reason why I quoted them. The other reason
being that Trevor had used the term "undynamic" which he backed up with
"compressed", which is a meaningful term that can be applied to electronics,
or even applied by electronics, though hopefully not in an amplifier used
below its clipping point.

The terms could be used to describe a piece of music but the amplifier
should leave such matters strictly alone and just make it big enough to
drive the speakers.

Well, yes he certainly spoke of compression in connection with a
MOSFET amp, but when I pressed him on it he first tried to change the
subject, then backed out of the discussion entirely. He has been
silent on the subject since.

I'm afraid Trevor is simply one of those benighted souls who have
swallowed the audiophile dictionary uncritically, and simply babbles
incomprehensibly (even by himself, it seems).

d

Opinion needed re power amp building
 

On 3 Nov, 23:27, "Trevor Wilson"
wrote:
"Don Pearce" wrote in message

...





On Wed, 4 Nov 2009 09:12:59 +1100, "Trevor Wilson"
wrote:

"Don Pearce" wrote in message
...
On Wed, 4 Nov 2009 08:47:13 +1100, "Trevor Wilson"
wrote:

We're discussing compression, which can be measured objectively -
please don't try to divert the discussion onto the metaphysical. Show
me compression.

**DBTs are not metaphysical. They allow REAL differences to be heard.
Tell
me about your experiences with DBTs between MOSFET and BJT amps.

Stop changing the subject. Either there is compression as you claim,
or there is not. Show me evidence of compression.

**I cannot. Try the test and let me know what you hear. Perhaps you will
have a different explanation. Negative tempco of gm is the only thing that
makes sense to me.

We are discussing one single parameter - compression. Once you start
with nonsense like seeing what you hear, you are no longer able to
isolate that parameter - you hear the sum of everything. And of course
mixed in with your "just listen" thing is all your bull****tery with
terms like "more dynamic". This is meaningless drivel, and the
standard recourse of the charlatan trying to claim superior skills of
discernment to the average man. It won't wash. You made the claim, now
substantiate it or withdraw it.

**I'm uncertain of what you are demanding I withdraw. Are you demanding that
I withdraw my theory that pertains to why MOSFET amps sound so bad? Or are
you demanding I withdraw what I and others hear?

Given the problems that many people hear with MOSFET amps, I proferred a
theory. I cannot validate that theory. If you have an alternate theory to
explain what people hear, then please present it.

As for claims of "superior skills of discernment", I make no such claims. My
hearing is just average. Anyone with average hearing will easily discern the
problems I speak of. I suggest you conduct your own test and confirm.
Perhaps you will develop a more credible theory.

--
Trevor Wilsonwww.rageaudio.com.au- Hide quoted text -

- Show quoted text -

More OSAF nonsense from Trevor. People do not hear 'problems' with
MOSFET (or any other properly functioning) amplifiers, they all sound
the same unless clipping. I still have on the cards an offer of £1,000
to anyone who can hear differences among amplifiers or cables under
level-matched DBT conditions. No one has even *tried* in the more than
ten years this offer has been on the table. I've tried it myself -
which is the point at which I stopped building amps and just bought
the cheapest that would drive my speakers properly. I still have my
trusty pure Class A Krell as a reference, but lots of others to which
I have *carefully* compared it sound exactly the same when driving
lighter speaker loads than my Apogees.

Opinion needed re power amp building
 

"Audionut" wrote


Audionut?

snip Trevor's silly *opinionating*


More OSAF nonsense from Trevor. People do not hear 'problems' with
MOSFET (or any other properly functioning) amplifiers, they all sound
the same unless clipping. I still have on the cards an offer of £1,000
to anyone who can hear differences among amplifiers or cables under
level-matched DBT conditions. No one has even *tried* in the more than
ten years this offer has been on the table. I've tried it myself -
which is the point at which I stopped building amps and just bought
the cheapest that would drive my speakers properly. I still have my
trusty pure Class A Krell as a reference, but lots of others to which
I have *carefully* compared it sound exactly the same when driving
lighter speaker loads than my Apogees.



****! I've *conjured up* Pinky by mentioning him!!

How about if I mention Trotsky - I wonder what he's doing these days? Coupla
dozen more 'names from the past' and this place'll be just like old times!!
(Then I'll *definitely* have to bugger off! :-)


Anyway, you're going to have to up your £1,000 challenge, Pinkus - it's
starting to look like Dr Evil holding the world to ransom for....

little finger in corner of mouth

.....**A MILLION DOLLARS**...!!

:-)