class A amplifier

[John Larkin]

On Fri, 17 Oct 2008 02:40:29 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

John Larkin wrote:

Eeyore wrote:
John Larkin wrote:
Eeyore wrote:
Rich Grise wrote:
Eeyore wrote:
"olivier.scalbert@algosyn.com" wrote:

I want to do a small class-A music amplifier + preamp. I want to find
the best trade-off between simplicity and sound quality.

Stop mucking about with stuff you don't understand and simply buy a modern
hi-fi amp.

Graham, don't be a dork. The guy wants to _BUILD_ stuff! He needs to be
encouraged - the "let's build it and see how it works" mentality is all
too rare these days.

I agree with the principle but it seems he hasn't done his homework first. His
present course of action is more likely to involve learning how to let the magic
smoke out. So I have directed him here ....
http://www.dself.dsl.pipex.com/ampins/ampins.htm

Where he will find a wealth of first class info.

The class A emitter follower is not a bad initial learning experiment,
and has some interesting variants. What's the point of just copying
old circuits? That's not design.

A Class A emitter follower ISN'T an old circuit ?

The point is that it's HIS circuit. And it has some potentially
interesting variations. IF you allow yourself to think.

It's a lousy circuit and I won't waste any time trying to dress up its well-known
shortcomings. If he wants a good class A output stage he needs to go back to the drawing
board.

Graham

What are the "well-known shortcomings" of a class-A emitter follower?

And what is your improved class A circuit?

John

 

[Eeyore]

John Larkin wrote:

Eeyore wrote:
John Larkin wrote:
"Phil Allison" wrote:
"John Larkin"

I sort of like the emitter follower with an active current sink.

** Yawnnnnnnn.

Having trouble staying awake again, I see. Do you guys get decent
coffee down there?

Better by far than the active current sink is the active DRIVEN transistor !

The logical conclusion is to stop playing with class A circuits and go
to Best Buy and get a Panasonic receiver.

Sanity reigns at last !

Incidentally do you know why the fixed emitter load resistor or current sink is
so crappy ?

Graham

 

[Eeyore]

John Larkin wrote:

Eeyore wrote:
John Larkin wrote:
Eeyore wrote:
John Larkin wrote:
Eeyore wrote:
Rich Grise wrote:
Eeyore wrote:
"olivier.scalbert@algosyn.com" wrote:

I want to do a small class-A music amplifier + preamp. I want to find
the best trade-off between simplicity and sound quality.

Stop mucking about with stuff you don't understand and simply buy a modern
hi-fi amp.

Graham, don't be a dork. The guy wants to _BUILD_ stuff! He needs to be
encouraged - the "let's build it and see how it works" mentality is all
too rare these days.

I agree with the principle but it seems he hasn't done his homework first. His
present course of action is more likely to involve learning how to let the magic
smoke out. So I have directed him here ....
http://www.dself.dsl.pipex.com/ampins/ampins.htm

Where he will find a wealth of first class info.

The class A emitter follower is not a bad initial learning experiment,
and has some interesting variants. What's the point of just copying
old circuits? That's not design.

A Class A emitter follower ISN'T an old circuit ?

The point is that it's HIS circuit. And it has some potentially
interesting variations. IF you allow yourself to think.

It's a lousy circuit and I won't waste any time trying to dress up its well-known
shortcomings. If he wants a good class A output stage he needs to go back to the >drawing
board.

What are the "well-known shortcomings" of a class-A emitter follower?

Start by thinking of the pull-up and pull-down current ability. And how that affects any
reactance on the load.

And what is your improved class A circuit?

Looks like a standard complementary emitter follower Class AB output but with the wick turned
up. Turn down the wick and it transitions from A to AB to B to C.

Graham

 

[Jamie]

Eeyore wrote:

"olivier.scalbert@algosyn.com" wrote:


Hello,

First, I must say that I have not done analog electronics since a long
time. So please be indulgent !

I want to do a small class-A music amplifier + preamp. I want to find
the best trade-off between simplicity and sound quality.

My approach is very incremental. I have started with one old 2N3055,
polarized with voltage divider composed of 2 resistors.

As the gain of the transistor is to low I finally put a (too?) small
BC546 in front of the 2N3055 (Darlington).
See schema:
http://scalbert.dyndns.org/electronics/amplifier/ampli1.png

As I need a preamp for the volume control, I have add another BC546 to
amplify the input signal.
See schema:
http://scalbert.dyndns.org/electronics/amplifier/preamp1.png

The DC is provided by a lab power supply (0-30V, 0-3A). I use from 5V
to 12V as the 2N3055 heatsink is to small.

When I first test it, I was expected to have a crappy and plastic
sound, and even smoke, but I was very surprised. The sound is clean
and contains a lot of details (speaker: B&W DM110).

What I want to do now is to improve:
- the schematic (there are certainly mistakes ...)
- the component choice (better capacitor ? , better transistor ?)

Any remarks and suggestions are welcomed !


Stop mucking about with stuff you don't understand and simply buy a modern
hi-fi amp. Power amps are a real speciality (especially if you want them
to be stable). It's no place for a beginner.
What a "Jack Ass" you are..

I didn't see any thing stated that he was looking for a high end
system other wise, I think he would have known enough to go out and do
just that how ever, it's seem evident that he is interested in the
workings of how it's done from the ground up!.

Do you understand stabilty criteria for example. What's a Bode plot ? etc

Do you understand that your a total jerk at times? wait, maybe all the

time
I could be mistaken there, it wouldn't be the first time.
\

Graham (designer of stable pro-audio power amps since 1980)

Yes Pro, of what, I have no idea..


http://webpages.charter.net/jamie_5"

 

[Eeyore]

Jamie wrote:

Eeyore wrote:

Graham (designer of stable pro-audio power amps since 1980)

Yes Pro, of what, I have no idea..

Try ebay.

Graham

 

[John Larkin]

On Sat, 18 Oct 2008 00:31:37 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

John Larkin wrote:

Eeyore wrote:
John Larkin wrote:
"Phil Allison" wrote:
"John Larkin"

I sort of like the emitter follower with an active current sink.

** Yawnnnnnnn.

Having trouble staying awake again, I see. Do you guys get decent
coffee down there?

Better by far than the active current sink is the active DRIVEN transistor !

The logical conclusion is to stop playing with class A circuits and go
to Best Buy and get a Panasonic receiver.

Sanity reigns at last !

Incidentally do you know why the fixed emitter load resistor or current sink is
so crappy ?

Graham

The current sink lets the output swing basically rail-to-rail, which
is better than the resistor can do. And it wastes less power on the
positive swing. Without inductors or transformers, it's about as good
as class A gets.

Starting with a resistor, and then using the current sink, I suppose
the next step would be to modulate the sink current. The efficiency
would go up, but it would retain most of the virtues of the emitter
follower... simplicity, low open-loop distortion, stability, low Zout.


John

 

[John Larkin]

On Fri, 17 Oct 2008 08:09:42 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Fri, 17 Oct 2008 02:38:08 +0100, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:



John Fields wrote:

Eeyore wrote:
Olivier Scalbert wrote:
Eeyore wrote:

I understand now. Now if you'd mentioned a bit of this in the OP, we might have
got off to a better start.

In my first post I have said that I have not done analog electronics
since a long time ...
which is true !

;-)
Anyway, no problem, we can continue ...

Oh, I doubt John Fields will allow that. He's a sad old git who will just shout me
down now. Shame since I could have taught you the whole gamut of output stage
operational ranges.

Awww...

And now you won't because I made you cry, poor baby, and it's my fault
that you won't help Olivier?

Indeed, because anything I say now, you will simply shoot down in flames.

---
If you have a defensible position, how could I?

I think this whole "gamut of output stage" thing is made up, but prove
me wrong; let's see what you've got...

JF

Does Eeyore ever post circuits?

John

 

[John Larkin]

On Sat, 18 Oct 2008 00:35:29 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

John Larkin wrote:

Eeyore wrote:
John Larkin wrote:
Eeyore wrote:
John Larkin wrote:
Eeyore wrote:
Rich Grise wrote:
Eeyore wrote:
"olivier.scalbert@algosyn.com" wrote:

I want to do a small class-A music amplifier + preamp. I want to find
the best trade-off between simplicity and sound quality.

Stop mucking about with stuff you don't understand and simply buy a modern
hi-fi amp.

Graham, don't be a dork. The guy wants to _BUILD_ stuff! He needs to be
encouraged - the "let's build it and see how it works" mentality is all
too rare these days.

I agree with the principle but it seems he hasn't done his homework first. His
present course of action is more likely to involve learning how to let the magic
smoke out. So I have directed him here ....
http://www.dself.dsl.pipex.com/ampins/ampins.htm

Where he will find a wealth of first class info.

The class A emitter follower is not a bad initial learning experiment,
and has some interesting variants. What's the point of just copying
old circuits? That's not design.

A Class A emitter follower ISN'T an old circuit ?

The point is that it's HIS circuit. And it has some potentially
interesting variations. IF you allow yourself to think.

It's a lousy circuit and I won't waste any time trying to dress up its well-known
shortcomings. If he wants a good class A output stage he needs to go back to the >drawing
board.

What are the "well-known shortcomings" of a class-A emitter follower?

Start by thinking of the pull-up and pull-down current ability. And how that affects any
reactance on the load.

It can sink whatever current the sink transistor is running at. It can
source whatever the emitter follower can pull up into the load + the
sink. That seems pretty simple.

John

 

[John Larkin]

On Sat, 18 Oct 2008 01:53:41 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

Jamie wrote:

Eeyore wrote:

Graham (designer of stable pro-audio power amps since 1980)

Yes Pro, of what, I have no idea..

Try ebay.

Graham

Does appearing on ebay make something "pro"?

http://cgi.ebay.com/LADYBUG-WITCH-Flying-Bats-Susan-Brack-HALLOWEEN-Art-SFA_W0QQitemZ150303033657QQcmdZViewItem?hash=item150303033657&_trkparms=72%3A1205|39%3A1|66%3A2|65%3A12|240%3A1318&_trksid=p3286.c0.m14

John

 

[Eeyore]

John Larkin wrote:

Eeyore wrote:
John Larkin wrote:
Eeyore wrote:
John Larkin wrote:
"Phil Allison" wrote:
"John Larkin"

I sort of like the emitter follower with an active current sink.

** Yawnnnnnnn.

Having trouble staying awake again, I see. Do you guys get decent
coffee down there?

Better by far than the active current sink is the active DRIVEN transistor !

The logical conclusion is to stop playing with class A circuits and go
to Best Buy and get a Panasonic receiver.

Sanity reigns at last !

Incidentally do you know why the fixed emitter load resistor or current sink is
so crappy ?

The current sink lets the output swing basically rail-to-rail, which
is better than the resistor can do. And it wastes less power on the
positive swing. Without inductors or transformers, it's about as good
as class A gets.

Aside from the actively driven load.

Starting with a resistor, and then using the current sink, I suppose
the next step would be to modulate the sink current. The efficiency
would go up, but it would retain most of the virtues of the emitter
follower... simplicity, low open-loop distortion, stability, low Zout.

Take your fixed resistor load amp, put some capacitance across the output and then
put a pulse waveform in. Got it now.

Then do it with the fixed current sink and and the active load.

You will see some interesting things.

Graham

 

[Eeyore]

John Larkin wrote:

I suppose
the next step would be to modulate the sink current. The efficiency
would go up, but it would retain most of the virtues of the emitter
follower... simplicity, low open-loop distortion, stability, low Zout.

That's what I've been saying all along. It looks like a standard class AB output
stage but with the bias turned right up into the amps region.

Graham

 

[Eeyore]

John Larkin wrote:

Does Eeyore ever post circuits?

Rarely since the copyright for most isn't mine.

Graham

 

[Eeyore]

John Larkin wrote:

Eeyore wrote:
John Larkin wrote:

What are the "well-known shortcomings" of a class-A emitter follower?

Start by thinking of the pull-up and pull-down current ability. And how that affects any
reactance on the load.

It can sink whatever current the sink transistor is running at. It can
source whatever the emitter follower can pull up into the load + the
sink. That seems pretty simple.

And they're not equal are they ? Even less equal with the resistor load. I learnt that about 37
years ago. Basic high-end pro-audio practice.

Graham

 

[Eeyore]

mrdarrett@gmail.com wrote:

John Larkin

Does Eeyore ever post circuits?

John

Why, yes...

http://groups.google.com/group/alt.audio.pro.live-sound/browse_frm/thread/a08f5aa5d31edd28/6a77ed3966d62e2b?lnk=gst&q=+Eyesore+rips+off+qsc#6a77ed3966d62e2b

Why do you ask? <wink

Please don't repeat libels. George Gleason is an idiot. It's actually one of his favourite companies, Behringer, who ripped off QSC's RMX design wholesale,
along with another outfit called Sekaku who sold it as an OEM product to a USA company under the Tapco label. They even used the same component designations.

How do I know ? They sent us a sample too. The first thing it did was blow up ! I despise copiers, regardless of any legal ramifications.

See the first response .....
"C'mon Curious George, don't you understand simple concepts of the Enghlish
language and mechanical design ?

"Adopted some techniques" does not mean "copied a design", especially if the
item is something as generic as mechanical contruction."

What I did was see a cute way to improve the way the top cover fitted and did something vaguely similar. It doesn't even look the same.

Graham

 

On Oct 17, 8:44 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:

On Fri, 17 Oct 2008 08:09:42 -0500, John Fields



jfie...@austininstruments.com> wrote:
On Fri, 17 Oct 2008 02:38:08 +0100, Eeyore
rabbitsfriendsandrelati...@hotmail.com> wrote:

John Fields wrote:

Eeyore wrote:
Olivier Scalbert wrote:
Eeyore wrote:

I understand now. Now if you'd mentioned a bit of this in the OP, we might have
got off to a better start.

In my first post I have said that I have not done analog electronics
since a long time ...
which is true !

;-)
Anyway, no problem, we can continue ...

Oh, I doubt John Fields will allow that. He's a sad old git who will just shout me
down now. Shame since I could have taught you the whole gamut of output stage
operational ranges.

Awww...

And now you won't because I made you cry, poor baby, and it's my fault
that you won't help Olivier?

Indeed, because anything I say now, you will simply shoot down in flames.

---
If you have a defensible position, how could I?

I think this whole "gamut of output stage" thing is made up, but prove
me wrong; let's see what you've got...

JF

Does Eeyore ever post circuits?

John

Why, yes...

http://groups.google.com/group/alt.audio.pro.live-sound/browse_frm/thread/a08f5aa5d31edd28/6a77ed3966d62e2b?lnk=gst&q=+Eyesore+rips+off+qsc#6a77ed3966d62e2b

Why do you ask? <wink>

Michael

 

[John Fields]

On Fri, 17 Oct 2008 20:44:53 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Fri, 17 Oct 2008 08:09:42 -0500, John Fields
jfields@austininstruments.com> wrote:

On Fri, 17 Oct 2008 02:38:08 +0100, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:



John Fields wrote:

Eeyore wrote:
Olivier Scalbert wrote:
Eeyore wrote:

I understand now. Now if you'd mentioned a bit of this in the OP, we might have
got off to a better start.

In my first post I have said that I have not done analog electronics
since a long time ...
which is true !

;-)
Anyway, no problem, we can continue ...

Oh, I doubt John Fields will allow that. He's a sad old git who will just shout me
down now. Shame since I could have taught you the whole gamut of output stage
operational ranges.

Awww...

And now you won't because I made you cry, poor baby, and it's my fault
that you won't help Olivier?

Indeed, because anything I say now, you will simply shoot down in flames.

---
If you have a defensible position, how could I?

I think this whole "gamut of output stage" thing is made up, but prove
me wrong; let's see what you've got...

JF

Does Eeyore ever post circuits?

---
I don't recall ever having seen one, and certainly nothing original.

JF

 

[Eeyore]

John Fields wrote:

John Larkin wrote:

Does Eeyore ever post circuits?

---
I don't recall ever having seen one, and certainly nothing original.

Oh there's plenty original (and some interesting variants on established concepts like using
pole-zero compensation in audio amps which is rare) but as ever it's the client's copyright.

Graham

 

[John Fields]

On Sat, 18 Oct 2008 08:27:00 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

John Larkin wrote:

Does Eeyore ever post circuits?

Rarely since the copyright for most isn't mine.

---
I don't think anyone's asking you to infringe copyrights, what you
never seem to do is post simple schematics of your contemporaneous
designs which would provide solutions for querents here.

JF

 

[John Fields]

On Sat, 18 Oct 2008 14:15:33 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

John Fields wrote:

John Larkin wrote:

Does Eeyore ever post circuits?

---
I don't recall ever having seen one, and certainly nothing original.

Oh there's plenty original (and some interesting variants on established concepts like using
pole-zero compensation in audio amps which is rare) but as ever it's the client's copyright.

---
Convenient, that...

JF

 

[Eeyore]

John Fields wrote:

Eeyore wrote:
John Larkin wrote:

Does Eeyore ever post circuits?

Rarely since the copyright for most isn't mine.

---
I don't think anyone's asking you to infringe copyrights, what you
never seem to do is post simple schematics of your contemporaneous
designs which would provide solutions for querents here.

Except I wouldn't want to post non-proven designs. And discrete stuff
(one of my strong points) does tend to need proving.

Graham