Opinion needed re power amp building
 

"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.

Here it is:

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

Take the time to listen for yourself. You might be surprised. I was.
---

Both amps were readily available in the US (and other places) and should be
very cheap and easy to obtain. No need to travel to Australia.

--
Trevor Wilson
www.rageaudio.com.au

Opinion needed re power amp building
 

In article ,
Trevor Wilson wrote:
*Depends on implementation. The MOSFETs, of course, will always sound
like MOSFETs - dull, boring, undynamic and compressed.

I've got a pair of 150w MOSFET amps in the workshop - so listen to them
quite a lot. Actually Maplin kits, but with a rather better power supply.
And they sound as sweet as a nut. Home made speakers too sort of thrown
together out of Audax units left over from a job. But one of those happy
coincidences that just work well.

--
*Don't use no double negatives *

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

Opinion needed re power amp building
 

On Wed, 4 Nov 2009 10:27:39 +1100, "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?


The one specific claim which is the ONLY one I have been discussing in
the face of your attempts to drag the conversation into the nebulous -
compression by MOSFET amplifiers.

irrelevant stuff snipped

d

Opinion needed re power amp building
 

In article , David Looser
wrote:
"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.

I'd also like to see the details of the circuits, methodology, and results.

I've often in the past compared amps made with MOSFETs with BJT. So far as
I could tell they were audibly indistinguishable provided you avoided
errors like trying to obtain power or current levels which a design could
not provide. And so far as I recall, all the published controlled tests
also show this. Certainly all the ones I've seen.

So where are the details of your DBT Trevor?

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 , 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? 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.

Where was the 'switch'?

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

Which 'amps' did you try? What were the details of the level matching,
avoidance of clipping/saturation etc?

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?

Given all the work, where did you publish the results? Since your results
seem to run contrary to all the published results I've seen - and I suspect
would have been welcomed by many 'subjective reviewers' I would expect them
to have been eager to have them published.

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.

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 , Trevor Wilson
wrote:

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

Your definition of "easy" seems to differ from mine. I do have new
neighbours moving in today though. Maybe they'll have the above amps to
loan me. :-)

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.

My problem here is that in the past I *have* repeately compared amps with
different types of op devices. And heard no differences due to that when
the amps were used within their drive limits and had much the same
frequency response, etc. i.e. were sensible designs.

In addition all the properly controlled blind comparisons I've seen
published results from that could be analysed return the same result.

So if your tests show otherwise it would be important to have all the
details published for examination and consideration.

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
 

"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.

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.

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

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.


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, 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.

Opinion needed re power amp building
 

Phil is probably right that I'll not gain much or ven anything from the
Hitachi design I have now.
But it will always niggle at me that there maybe a better design nowadays.
MOS appeals from the robustness angle but I'm not convinced it's best for
audio, relatively few manufacturers seem to go that route apart from in car
audio..........
So this is my current target

http://www.tech-diy.com/Amplifiers/L...702_Sanken.htm

I take on board that the SAP15's may go out of exisitence in the future but
I could always change the output stage to something else should the worst
happen.
I even have 2 pair of SAP01M fets but looking around they don't appear to be
stocked so they must have been a non-starter ( I got them as samples when
they came out )

thanks for all your comments.

Pete

Opinion needed re power amp building
 

"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.



.... Phil

Opinion needed re power amp building
 

"Phil Allison" wrote in message
...

"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.



.... Phil







Phil,

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."


Pete