Opinion needed re power amp building
 

"Pete"
"Phil Allison"
"Pete"

Phil is probably right that I'll not gain much or ven anything from the
Hitachi design I have now.

** Huh ???

Are there posts from me here in invisible ink now ??

Cos I cannot see what the OP is replying to.


Sorry, I was flicking through all the replies and took your reply a little
out of context. There was a lot to digest ( is my excuse.....)

"** Those are Hitachi's famous TO3 pack " lateral " mosfets as used in
many
famous hi-fi and professional power amps.

They are extremely easy to use, exceptionally rugged and have NO issues
with biasing or bias stability. Plus they will share current automatically
when used in parallel."


** Where is there any connection between my post and your comment at the top
???

Must be in invisible ink - right ?



...... Phil

Opinion needed re power amp building
 

"Arny Krueger" wrote in message
...
"Trevor Wilson" wrote in
message
"Arny Krueger" wrote in message
...
"David Looser" wrote in
message
"Trevor Wilson" wrote

**DBTs are not metaphysical. They allow REAL
differences to be heard. Tell me about your
experiences with DBTs between MOSFET and BJT amps.
I'd be interested to know how these DBTs were conducted.
How many listeners did you use?, how were they
recruited, how much did they know about the purpose of
the test? etc.

In the end you've got to go to Australia to see Trevor
prove his point. I've been down this road with him
before in his anti-loop-feedback days.

**Perhaps you missed my last post to you.

Not at all.

Your suggest is actually less practical than me catching the next flight
to down under.

(True! read below!)

Here it is:

---
**I'll make it easy for you. Locate an old Phase Linear
400(b)

I don't have any, and don't know anybody who currently has one.

If I wanted to buy one, they seem to be going for about $500 on eBay.

**Sorry. It's as easy as I can make it. Old Phase Linear amps are very
common over here. I'd assumed they'd be just as common in the US.


and an early Perreaux amp.

I don't have any, and don't know anybody who even ever had one.

I don't even know what the model number would be, since you are so vague
in describing it.

**Model 2150.


I see that I could pick a fairly decent Perreaux amp up for $1,500 on
eBay.

**Given that it is a crap amp, but reliable, colour me surprised that they
sell for so much.


Northwest airlines will sell me a round trip ticket from DTW to SYD for
$1,295.

I have proven that your suggestion is even less practical than what I
first suggested.

**Only for you. I provided a most economical solution.



Set up a DBT between
the two and ask the listeners what differences they feel
they can hear (if any). Let me know what results you
find. Both amps are plentiful and cheap, so the test
should be an easy one. Both amps use ****-loads of global
NFB, minimal bias current and primitive topology so the
only major differences are related to the output devices
used.


The real truth Trevor is that if all amplifiers sounded as different as
you claim

**BZZZTTT! I claimed nothing of the sort. I claimed that the Phase Linear
400(b) sounds different to a Perreaux 2150.

, there would be a world of amps that would DBT different, not just an
early SS old-timer well-known for being a loser (whether true or not) and
some esoteric wunder-amp.

**We're discussing Phase Linear and Perreaux amps from the late 1970s and
early 1980s.


--
Trevor Wilson
www.rageaudio.com.au

Opinion needed re power amp building
 

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

"David Looser" wrote in message
...
"Trevor Wilson" wrote

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

I'd be interested to know how these DBTs were conducted. How many
listeners did you use?

**10. I arranged for a person who had no knowledge of which amp (he was
no present at set-up time) was which to throw the switch, whilst
keeping a record of which position the switch was in at each change. I
set the equipment up and was present for the test, but took no part.

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.


Where was the 'switch'?

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


, 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.


The listeners were all those who considered themselves to be
audiophiles. They were not 'people off the street'. I was already
familiar with the listening preferences of each. They were tested in
groups of two, over a period of several days.

I performed the test, because I heard about these "new" (back in the
early 1980s) MOSFET amps and how wonderful they allegedly were. I was
surprised at how bad they sounded, despite glowing reviews in places
like Stereophile. I decided to recruit others to see if their
perceptions agreed with mine. They did. All listeners reported similar
findings. The MOSFET amps sounded 'compressed' and lacking in dynamics.

Raw data of results?

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

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

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


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 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.


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?

- 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.


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?


--
Trevor Wilson
www.rageaudio.com.au

Opinion needed re power amp building
 

"Trevor Wilson" wrote

**We're discussing Phase Linear and Perreaux amps from the late 1970s and
early 1980s.


OK, good. So this is nothing to do with MOSFETS in general, merely one
particular rather ancient amplifier. Glad we got that clarified.

David.

Opinion needed re power amp building
 

"Trevor Wilson" wrote

**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.


Why a light? It's existence reduces the validity of your results. The
listeners should not only not know which amp is 'A' and which 'B'. They
should not know whether, at any given time, they are listening to 'A' or
'B'. Listeners will often give a preference when asked to compare 'A' to 'A'
or 'B' to 'B' because they think there *ought* to be a difference! Ideally
they should not even know that the test is a comparative test of amps
(rather than say sources or cables).

David.

Opinion needed re power amp building
 

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. 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.


Where was the 'switch'?

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

No. I meant where in the experimental system?


, 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*?

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.

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.

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?


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

How did you monitor for any current limiting or clipping *during the
tests*? The problem here is that real-world speakers can be more demanding
of current that you might be aware when playing music.


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.


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'?

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?

- 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?

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.

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

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.

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.

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.

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?

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
 

In article , David Looser
wrote:
"Trevor Wilson" wrote

**We're discussing Phase Linear and Perreaux amps from the late 1970s
and early 1980s.


OK, good. So this is nothing to do with MOSFETS in general, merely one
particular rather ancient amplifier. Glad we got that clarified.

Yes. If that is the case then it makes more sense to me since I have also
encountered some amps that 'sounded different' because they had some flaw
or limitation in the design. Given some of the weirder designs that are
sold to 'audiophiles' I find it quite plausible. But it may tell us nothing
about MOSFET vs Bipolar as classes when used appropriately within their
limits.

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
 

"Phil Allison" wrote in message
...

"Pete"
"Phil Allison"
"Pete"

Phil is probably right that I'll not gain much or ven anything from the
Hitachi design I have now.

** Huh ???

Are there posts from me here in invisible ink now ??

Cos I cannot see what the OP is replying to.


Sorry, I was flicking through all the replies and took your reply a
little out of context. There was a lot to digest ( is my excuse.....)

"** Those are Hitachi's famous TO3 pack " lateral " mosfets as used in
many
famous hi-fi and professional power amps.

They are extremely easy to use, exceptionally rugged and have NO issues
with biasing or bias stability. Plus they will share current
automatically
when used in parallel."


** Where is there any connection between my post and your comment at the
top ???

Must be in invisible ink - right ?



..... Phil



OK Phil, no connection, sorry.

I have re-read the posts and it was Woody who said

"Why bother? The basic Hitachi design is as good as it gets. You can improve
things by building a proper regulated power supply for it."

Pete

Opinion needed re power amp building
 

"Jim Lesurf" wrote in message

In article , David
Looser wrote:
"Trevor Wilson" wrote

**We're discussing Phase Linear and Perreaux amps from
the late 1970s and early 1980s.

OK, good. So this is nothing to do with MOSFETS in
general, merely one particular rather ancient amplifier.
Glad we got that clarified.

IOW, it is essentially OT to the OP and most of the discussion that followed
it.

Yes. If that is the case then it makes more sense to me
since I have also encountered some amps that 'sounded
different' because they had some flaw or limitation in
the design.

However, there's no reliable evidence that the amps that Trevor mentioned
have this kind of flaw.

So Trevor's proposed test is doubly irrelevant. It's not about the kind of
amps that this thread was created to discuss, and there's no reliable
evidence that the amps he mentioned actually have audible design flaws as
typically used.

Given some of the weirder designs that are
sold to 'audiophiles' I find it quite plausible.

Aside from that, there is a lot of audiophile lore and legend about certain
amps always sounding bad, when said amps in good operating condition
actually sound OK. Any amp that was sold in large volumes and may have been
prone to failure might be getting this kind of treatment. This is especially
true if the amp has a common failure mode that does not completely disable
it.

But it
may tell us nothing about MOSFET vs Bipolar as classes
when used appropriately within their limits.

Exactly. My audio club has examined this issue in some depth and no
surprise, we found that a properly-designed amp in good operating condition
sounds great, no matter which type of output device is used.

There is a precident for this. There was a class of SS output device that
was widely used and has completely fallen into complete disuse. But, that
did not happen to either MOSFET or Bipolar technology. I suspect that if
marketing stats were avaialble we'd find that there was a time when MOSFET
usage increased dramatically and obtained a fair market share. Since then,
MOSFET use has probably decreased, but there is still significant use of it.

The engineers I talk to say that linear (not switchmode) MOSFET amps tend to
be more costly and less efficient for a given power and performance level.
Note that a long-time advocate of FET power amps for audio, namely Hafler is
no longer in production. Haflers had a reputation for sounding great but
being costly and inefficient. Not all that inefficient, but audio can be a
very competitive business.

Opinion needed re power amp building
 

"Pete"

** Where is there any connection between my post and your comment at the
top ???

Must be in invisible ink - right ?

OK Phil, no connection, sorry.

I have re-read the posts and it was Woody who said ...


** Apology accepted.

Basic usenet etiquette requires you ALWAYS post UNDER any words you are
referring to.

There is BLOODY SIMPLE reason for that !!!!

Capice ???????



..... Phil