class A amplifier

[Olivier Scalbert]

mrdarrett@gmail.com wrote:

These look interesting too.
http://sound.westhost.com/project12a.htm
http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm

The H. C. Lin amplifier from 1956 started the whole Class AB (B?)
thing, eh?

Michael

Thanks for the links Michael.
Little question:
if I use this type of circuit with a symmetrical power supply do you
think I can remove C7 (if the Q6 collector is at 0v)? Then how can I
manage the retro-action (R7/R4) ?

Olivier

 

[Eeyore]

John Fields wrote:

Eeyore 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...

There was a whole shedload of my circuits on the studiomaster site but some clot handed them over
to a pay site.

I must mention that to the MD, was talking to him earlier.

Graham

 

[John Larkin]

On Fri, 17 Oct 2008 22:44:37 -0700 (PDT), mrdarrett@gmail.com wrote:

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

Sorry, I meant to ask if he ever posts original circuits.

John

 

[John Larkin]

On Sat, 18 Oct 2008 08:29:14 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

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 ?

Doesn't matter what the capability of the drives are; all the load
sees is the voltage it sees.

Your favorite ancient complementary bipolar class AB stage seldom has
symmetric output current capability; again, it doesn't matter if the
load is driven properly.

John

 

[Jamie]

Eeyore 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.

Graham

Any one have a violin to play, I've broke mine listening to Graham.

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

 

[Kevin Aylward]

Eeyore wrote:

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.

Yes, if you want performance, you really want a signal active source and
sink.
With a constant current sink, the other transistor has to drive that one as
well as the load. If it's active, then the other transistor, has less work
to
do, and all its current goes to its load. That's why I developed the
configuration I showed before ( the local output feedback loop one
http://www.kevinaylward.co.uk/ee/circuits/VeryLowDistortionAmp2.jpg).



Kevin Aylward
www.blonddee.co.uk
www.kevinaylward.co.uk

 

[John Larkin]

On Sat, 18 Oct 2008 17:03:19 GMT, "Kevin Aylward"
<kaExtractThis@kevinaylward.co.uk> wrote:

Eeyore wrote:


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.



Yes, if you want performance, you really want a signal active source and
sink.
With a constant current sink, the other transistor has to drive that one as
well as the load. If it's active, then the other transistor, has less work
to
do, and all its current goes to its load. That's why I developed the
configuration I showed before ( the local output feedback loop one
http://www.kevinaylward.co.uk/ee/circuits/VeryLowDistortionAmp2.jpg).



Kevin Aylward
www.blonddee.co.uk
www.kevinaylward.co.uk

Did you ever actually build it?

John

 

[Eeyore]

Olivier Scalbert wrote:

mrdarrett@gmail.com wrote:

These look interesting too.
http://sound.westhost.com/project12a.htm
http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm

The H. C. Lin amplifier from 1956 started the whole Class AB (B?)
thing, eh?

Michael

Thanks for the links Michael.
Little question:
if I use this type of circuit with a symmetrical power supply do you
think I can remove C7 (if the Q6 collector is at 0v)? Then how can I
manage the retro-action (R7/R4) ?

Build yourself a complementary output stage. The you can change the
quiescent current from A though AB to B and finally C and HEAR the
difference. AND yes, it can be DC coupled.

It's also by FAR the 'best' configuration audio wise and as efficient as
it gets.

Graham

 

[Eeyore]

John Larkin wrote:

Sorry, I meant to ask if he ever posts original circuits.

Wel, aside from 'obvious circuits' prior art et all what do you expect ? But I have no intention of giving away my design tricks publicly to the Chinese.

Graham

 

[Eeyore]

John Larkin wrote:

Eeyore wrote:
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 ?

Doesn't matter what the capability of the drives are; all the load
sees is the voltage it sees.

You're not thinking clearly dV/dt = I/C

Graham

 

[Eeyore]

John Larkin wrote:

Your favorite ancient complementary bipolar class AB stage seldom has
symmetric output current capability;

Really ?

again, it doesn't matter if the load is driven properly.

And what is 'properly' ?

Graham

 

[Eeyore]

Jamie wrote:

Eeyore 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.

Any one have a violin to play, I've broke mine listening to Graham.

If Studiomaster hadn't shut down free public access to their schematics you could see loads of
them.

Graham

 

[John Larkin]

On Sat, 18 Oct 2008 18:39:22 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

John Larkin wrote:

Your favorite ancient complementary bipolar class AB stage seldom has
symmetric output current capability;

Really ?

Really.

again, it doesn't matter if the load is driven properly.

And what is 'properly' ?

It gets the voltage waveform the designer intended that it get.

John

 

[Eeyore]

John Larkin wrote:

Eeyore wrote:
John Larkin wrote:

Your favorite ancient complementary bipolar class AB stage seldom has
symmetric output current capability;

Really ?

Really.

Not to any extent worth worrrying over.

again, it doesn't matter if the load is driven properly.

And what is 'properly' ?

It gets the voltage waveform the designer intended that it get.

And you think that's about "if the load is driven properly" ? Don't leave
your day job would be my advice.

Graham

 

[Michael A. Terrell]

Eeyore wrote:

John Larkin wrote:

Eeyore wrote:
John Larkin wrote:

Your favorite ancient complementary bipolar class AB stage seldom has
symmetric output current capability;

Really ?

Really.

Not to any extent worth worrrying over.

again, it doesn't matter if the load is driven properly.

And what is 'properly' ?

It gets the voltage waveform the designer intended that it get.

And you think that's about "if the load is driven properly" ? Don't leave
your day job would be my advice.

Why would he want to? He designs high power amplifiers for medical
equipment that you couldn't.


--
http://improve-usenet.org/index.html

aioe.org, Goggle Groups, and Web TV users must request to be white
listed, or I will not see your messages.

If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm


There are two kinds of people on this earth:
The crazy, and the insane.
The first sign of insanity is denying that you're crazy.

 

[John Larkin]

On Sat, 18 Oct 2008 21:00:18 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

John Larkin wrote:

Eeyore wrote:
John Larkin wrote:

Your favorite ancient complementary bipolar class AB stage seldom has
symmetric output current capability;

Really ?

Really.

Not to any extent worth worrrying over.


again, it doesn't matter if the load is driven properly.

And what is 'properly' ?

It gets the voltage waveform the designer intended that it get.

And you think that's about "if the load is driven properly" ? Don't leave
your day job would be my advice.

My day job is designing electronics. About $200 million or so of it,
so far.

John

 

[Eeyore]

"Michael A. Terrell" wrote:

Eeyore wrote:
John Larkin wrote:
Eeyore wrote:
John Larkin wrote:

Your favorite ancient complementary bipolar class AB stage seldom has
symmetric output current capability;

Really ?

Really.

Not to any extent worth worrrying over.

again, it doesn't matter if the load is driven properly.

And what is 'properly' ?

It gets the voltage waveform the designer intended that it get.

And you think that's about "if the load is driven properly" ? Don't leave
your day job would be my advice.

Why would he want to? He designs high power amplifiers for medical
equipment that you couldn't.

I wouldn't bet on that.

I've fixed 3 'runaways' including one in marine radar. I could tell you a story
or two about that. I turned a turkey into a significant commercial success.
There was a restructuring going on at the time. The Technical Director was being
promoted to Managing Director, his Technical Manager was becoming Technical
Director and quite a few of the R&D staff suggested I should apply for the open
Technical Manager post (staff of about 40).

I was VERY flattered.

Graham

 

[John Fields]

On Sat, 18 Oct 2008 17:17:52 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

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.

---
So prove it.

If, in fact, discrete analog design is one of your strong points, you'd
know that if you're introducing some nuance into a previously proven
design and, therefore, don't know about the nitty-gritty of the combo
and/or you don't know how to simulate it properly, Then you need to
build a few a of them, test them over the expected changes in supply
voltage, ambient temperature, and load impedance, and report your
findings.

JF

 

[Eeyore]

John Larkin wrote:

Eeyore wrote:
John Larkin wrote:
Eeyore wrote:
John Larkin wrote:

Your favorite ancient complementary bipolar class AB stage seldom has
symmetric output current capability;

Really ?

Really.

Not to any extent worth worrrying over.

again, it doesn't matter if the load is driven properly.

And what is 'properly' ?

It gets the voltage waveform the designer intended that it get.

And you think that's about "if the load is driven properly" ? Don't leave
your day job would be my advice.

My day job is designing electronics. About $200 million or so of it,
so far.

Well you beat me there by a factor of 3 or so.

Graham

 

[John Fields]

On Sat, 18 Oct 2008 17:22:19 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

John Fields wrote:

Eeyore 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...

There was a whole shedload of my circuits on the studiomaster site but some clot handed them over
to a pay site.

I must mention that to the MD, was talking to him earlier.

---
The buck stops where?

JF