[Scott Dorsey]

Bret Ludwig wrote:
High bias AB amps operate in class A through most of the power range
they spend all their time in, giving the advantage of Calss A operation
where it is needed, and rather than running out of power when this is
exceeded they simply transition into Class B.

This is true. The problem, however, is that although the distortion may
be much lower in class AB than in class B, the distortion spectrum is often
less pleasant, at least to my ear. I often find a given output stage sounds
better biased into class B than up higher into class AB.

For low power studio-grade applications, though, there's no reason not to
just go whole-hog and run everything Class A. Electricity is cheap.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Trevor Wilson]

"Scott Dorsey" wrote in message
...
Bret Ludwig wrote:
High bias AB amps operate in class A through most of the power range
they spend all their time in, giving the advantage of Calss A operation
where it is needed, and rather than running out of power when this is
exceeded they simply transition into Class B.

This is true. The problem, however, is that although the distortion may
be much lower in class AB than in class B, the distortion spectrum is
often
less pleasant, at least to my ear. I often find a given output stage
sounds
better biased into class B than up higher into class AB.

**Bull****. Only poorly deisgned Class A/B amps sound significantly worse
than an otherwise identical Class A amp. Pay careful attention to my words:
"Otherwise identical".


For low power studio-grade applications, though, there's no reason not to
just go whole-hog and run everything Class A. Electricity is cheap.

**There are plenty of reasons NOT to go pure Class A and very few to do so.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Scott Dorsey]

Trevor Wilson wrote:
"Scott Dorsey" wrote in message
...
Bret Ludwig wrote:
High bias AB amps operate in class A through most of the power range
they spend all their time in, giving the advantage of Calss A operation
where it is needed, and rather than running out of power when this is
exceeded they simply transition into Class B.

This is true. The problem, however, is that although the distortion may
be much lower in class AB than in class B, the distortion spectrum is
often
less pleasant, at least to my ear. I often find a given output stage
sounds
better biased into class B than up higher into class AB.

**Bull****. Only poorly deisgned Class A/B amps sound significantly worse
than an otherwise identical Class A amp. Pay careful attention to my words:
"Otherwise identical".

That's not what I said. That is not at ALL what I said.

For low power studio-grade applications, though, there's no reason not to
just go whole-hog and run everything Class A. Electricity is cheap.

**There are plenty of reasons NOT to go pure Class A and very few to do so.

Other than size and heat?
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Trevor Wilson]

"Scott Dorsey" wrote in message
...
Trevor Wilson wrote:
"Scott Dorsey" wrote in message
...
Bret Ludwig wrote:
High bias AB amps operate in class A through most of the power range
they spend all their time in, giving the advantage of Calss A operation
where it is needed, and rather than running out of power when this is
exceeded they simply transition into Class B.

This is true. The problem, however, is that although the distortion may
be much lower in class AB than in class B, the distortion spectrum is
often
less pleasant, at least to my ear. I often find a given output stage
sounds
better biased into class B than up higher into class AB.

**Bull****. Only poorly deisgned Class A/B amps sound significantly worse
than an otherwise identical Class A amp. Pay careful attention to my
words:
"Otherwise identical".

That's not what I said. That is not at ALL what I said.

For low power studio-grade applications, though, there's no reason not
to
just go whole-hog and run everything Class A. Electricity is cheap.

**There are plenty of reasons NOT to go pure Class A and very few to do
so.

Other than size and heat?

**Cost, reliability and the fact that high bias Class A/B is lower in
distortion.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Eeyore]

Trevor Wilson wrote:

"Scott Dorsey" wrote
Trevor Wilson wrote:

**There are plenty of reasons NOT to go pure Class A and very few to do
so.

Other than size and heat?

**Cost, reliability and the fact that high bias Class A/B is lower in
distortion.

Lower ?

Graham

[Trevor Wilson]

"Eeyore" wrote in message
...


Trevor Wilson wrote:

"Scott Dorsey" wrote
Trevor Wilson wrote:

**There are plenty of reasons NOT to go pure Class A and very few to do
so.

Other than size and heat?

**Cost, reliability and the fact that high bias Class A/B is lower in
distortion.

Lower ?

**Yup. Self has provided convincing proof of this.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Arny Krueger]

"Trevor Wilson" wrote in
message
"Eeyore" wrote
in message ...


Trevor Wilson wrote:

"Scott Dorsey" wrote
Trevor Wilson wrote:

**There are plenty of reasons NOT to go pure Class A
and very few to do so.

Other than size and heat?

**Cost, reliability and the fact that high bias Class
A/B is lower in distortion.

Lower ?

**Yup. Self has provided convincing proof of this.

Agreed.

I would hope that this paper would be required reading for any
self-appointed power amp guru:

http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm

[Arny Krueger]

"Eeyore" wrote in
message
Trevor Wilson wrote:

"Scott Dorsey" wrote
Trevor Wilson wrote:

**There are plenty of reasons NOT to go pure Class A
and very few to do so.

Other than size and heat?

**Cost, reliability and the fact that high bias Class
A/B is lower in distortion.

Lower ?

Yes, there are two problems with class A - both related to the fact that
with class A, the output stage always has far more current flowing in it.

(1) Power transistors tend to be less linear at high currents - the beta
falls off. Running an output stage class A approximately doubles the
current that the output stage has to handle. So, you move the operating
point way out on the output devices.

(2) Less SOA from the perspective of the load, because the output devices
are pulling so hard against each other.

[Phil Allison]

"Arny Krueger"


Yes, there are two problems with class A - both related to the fact that
with class A, the output stage always has far more current flowing in it.

(1) Power transistors tend to be less linear at high currents - the beta
falls off. Running an output stage class A approximately doubles the
current that the output stage has to handle. So, you move the operating
point way out on the output devices.

(2) Less SOA from the perspective of the load, because the output devices
are pulling so hard against each other.


** What a load of complete DRIVEL !!!!

Arny - leave commenting on power amp design to people who know something
about it cos they spend their lives dealing with it at component level.

Cos YOU do not have a bloody clue.




......... Phil

[Bertie the Bunyip]

Eeyore wrote in
:



Trevor Wilson wrote:

"Scott Dorsey" wrote
Trevor Wilson wrote:

**There are plenty of reasons NOT to go pure Class A and very few
to do so.

Other than size and heat?

**Cost, reliability and the fact that high bias Class A/B is lower in
distortion.

Lower ?

Graham



fjukkwit netkkkoping ****


Bertie

[Trevor Wilson]

"Scott Dorsey" wrote in message
...
Trevor Wilson wrote:
"Scott Dorsey" wrote in message
...
Bret Ludwig wrote:
High bias AB amps operate in class A through most of the power range
they spend all their time in, giving the advantage of Calss A operation
where it is needed, and rather than running out of power when this is
exceeded they simply transition into Class B.

This is true. The problem, however, is that although the distortion may
be much lower in class AB than in class B, the distortion spectrum is
often
less pleasant, at least to my ear. I often find a given output stage
sounds
better biased into class B than up higher into class AB.

**Bull****. Only poorly deisgned Class A/B amps sound significantly worse
than an otherwise identical Class A amp. Pay careful attention to my
words:
"Otherwise identical".

That's not what I said. That is not at ALL what I said.

**True. What you said was bull****. Now, pay attention to my words. Focus
on: "Otherwise identical". Also focus on: "Poorly designed". If you, like I
have, taken a well designed Class A/B amp and cranked the bias current up to
100 Watts Class A, you will have noted no sonic differences between the
Class A/B operation and the Class A operation. OTOH, I have taken crappily
designed Class A/B amps and cranked the bias up to high levels of Class A
and found significant sonic improvements from doing so.

IOW: The design is more important than the Class of operation. Class A will
help a bad design and, at best, do nothing to a good design.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Eeyore]

Trevor Wilson wrote:

IOW: The design is more important than the Class of operation. Class A will
help a bad design and, at best, do nothing to a good design.

You're assuming they all start as Class AB output stages there.

Graham

[Trevor Wilson]

"Eeyore" wrote in message
...


Trevor Wilson wrote:

IOW: The design is more important than the Class of operation. Class A
will
help a bad design and, at best, do nothing to a good design.

You're assuming they all start as Class AB output stages there.

**That's because there are essentially no Class A push pull designs
(anymore). They're all Class A/B with different bias currents.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Eeyore]

Trevor Wilson wrote:

"Eeyore" wrote in message
Trevor Wilson wrote:

IOW: The design is more important than the Class of operation. Class A
will
help a bad design and, at best, do nothing to a good design.

You're assuming they all start as Class AB output stages there.

**That's because there are essentially no Class A push pull designs
(anymore). They're all Class A/B with different bias currents.

That's where I plan to differ.

Now. To get back to the original question.... Have you heard a noticeable
difference between Class A and A/B ?

Graham

[Arny Krueger]

"Trevor Wilson" wrote in
message
"Eeyore" wrote
in message ...


Trevor Wilson wrote:

IOW: The design is more important than the Class of
operation. Class A will
help a bad design and, at best, do nothing to a good
design.

You're assuming they all start as Class AB output stages
there.

**That's because there are essentially no Class A push
pull designs (anymore). They're all Class A/B with
different bias currents.

Agreed again. Building a truely Class A power amp that can deliver
significant amounts of power output is really a pretty awesome thing. The
OPT stage quiescent current has to be equal to the *peak* current that is
delivered to the load.

We all know that speakers can be capacitive-reactive and can jack the load
current to unexpectedly high levels. A common power amp will have +/- 80
volt DC rails and may need to deliver up to 15 amps peak to the load. So,
now the OPT is dissipating 2400 watts per channel just sitting there, not
counting internal losses.

Considering that heavy duty electrical room heaters usually top out around
1600 watts, the problem should be self-evident. We're basically talking a
power amp that duplicates the heating function of 3 room heaters and has to
be hooked up to a clothes dryer circuit.

[Bertie the Bunyip]

Eeyore wrote in
:



Trevor Wilson wrote:

IOW: The design is more important than the Class of operation. Class
A will help a bad design and, at best, do nothing to a good design.

You're assuming they all start as Class AB output stages there.

Graham



netkkkoping piece of ****/



Bertie

[Scott Dorsey]

Trevor Wilson wrote:

**True. What you said was bull****. Now, pay attention to my words. Focus
on: "Otherwise identical". Also focus on: "Poorly designed". If you, like I
have, taken a well designed Class A/B amp and cranked the bias current up to
100 Watts Class A, you will have noted no sonic differences between the
Class A/B operation and the Class A operation. OTOH, I have taken crappily
designed Class A/B amps and cranked the bias up to high levels of Class A
and found significant sonic improvements from doing so.

No, that bears no connection with what I said. I said that if you take a
class B amplifier and crank the gain up into the A/B range, that the sound
quality may be subjectively worse even though the THD is reduced. I said
nothing at ALL about full class A operation.

IOW: The design is more important than the Class of operation. Class A will
help a bad design and, at best, do nothing to a good design.

Absolutely.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Eeyore]

Scott Dorsey wrote:

Trevor Wilson wrote:

**There are plenty of reasons NOT to go pure Class A and very few to do so.

Other than size and heat?

That's what I'm working on you see !

Graham

[Bertie the Bunyip]

Eeyore wrote in
:



Scott Dorsey wrote:

Trevor Wilson wrote:

**There are plenty of reasons NOT to go pure Class A and very few to
do so.

Other than size and heat?

That's what I'm working on you see !

Graham



lying kjuuunnntt



Bertie

[hank alrich]

Scott Dorsey wrote:

**Bull****. Only poorly deisgned Class A/B amps sound significantly worse
than an otherwise identical Class A amp. Pay careful attention to my words:
"Otherwise identical".

That's not what I said. That is not at ALL what I said.

This is obviously Filly Assilon. It can neither hear nor read with its
head in there.

--
ha

[Eeyore]

hank alrich wrote:

Scott Dorsey wrote:

**Bull****. Only poorly deisgned Class A/B amps sound significantly worse
than an otherwise identical Class A amp. Pay careful attention to my words:
"Otherwise identical".

That's not what I said. That is not at ALL what I said.

This is obviously Filly Assilon. It can neither hear nor read with its
head in there.

Actually it was another Australian !

You've comitted the cardinal sin now. Prepare to be roasted.

Graham

[hank alrich]

Trevor Wilson wrote:

**Bull****. Only poorly deisgned Class A/B amps sound significantly worse
than an otherwise identical Class A amp. Pay careful attention to my words:
"Otherwise identical".

Guess who this asshole is.

--
ha