class A amplifier

[Olivier Scalbert]

YD wrote:

Go to http://www.sillanumsoft.org for the free Visual Analyzer. It
works both as a function generator and an audio analyzer. The scope
might be useful for calibrating the settings.

- YD.

Thanks for the link !
olivier

 

[John Larkin]

On Wed, 15 Oct 2008 18:15:50 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

"Olivier Scalbert"

Agree, but I have no negative supply yet. I have to found or buy or build
one.



** Consider changing you circuit to include an inductor in place of the load
resistor - best if you put one in the collector circuit.

Schematic?

John

 

[John Larkin]

On Wed, 15 Oct 2008 11:05:59 -0300, YD <ydtechHAT@techie.com> wrote:

Late at night, by candle light, John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> penned this immortal
opus:

On Tue, 14 Oct 2008 17:36:08 +0200, Olivier Scalbert
olivier.scalbert@algosyn.com> wrote:

John Larkin wrote:
Hey, this is usenet. It selectively attracts the willfully ignorant,
the arrogant, and the pain sluts who crave public humiliation.

Why not drive the base of your darlington with an opamp?

John

egos ... !

I still have some LM741 but it is perhaps too short no ? What do you
suggest ?

Olivier

Ideally you'd use a driver stage that is fast, quiet, and swings to
both power rails. 741 does none of the above.

Something like LM7301 might be OK for starters.

John



I like the TL07x series. Cheap, plentiful and quite stable unless you
hang too much capacitance on the output, and there's a simple way out
of that.

- YD.

It won't swing to the rails, so throws away power output capability.

The class A emitter follower isn't efficient, but it is interesting.
It has inherent low Zout and low distortion, and is simple and stable,

John

 

[John Larkin]

On Wed, 15 Oct 2008 02:18:47 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

John Larkin wrote:

Eeyore wrote:
John Larkin wrote:
Olivier Scalbertwrote:
Eeyore wrote:

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.

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

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

I have studied Bode, Nyquist, Smith diagrams, Z, Laplace, Fourier
transformations and their digital implementations, ...

So I think I can read technical answers to my "beginners" questions.

Oh, by the way, I must admit that I have miss the training "how to
become arrogant".

Hey, this is usenet. It selectively attracts the willfully ignorant,
the arrogant, and the pain sluts who crave public humiliation.

Why not drive the base of your darlington with an opamp?

The BC546 is far too tiny to drive a 2N3055 intelligently. It's TO-92 FFS but you
Americans aren't so familiar with our European (Pro-Electron) devices are you ?

Of course we aren't. We use BCX70's and BAV99's, but they're just part
numbers, like 2N7002 is a part number. What's wrong with 2N?

Nothing whatever, along with 2SA, SB, SC, SD, SJ and SK either. And sone Non - Jedec,
Jeida or Pro-Electron devices that are 'house parts'.


"Pro-Electron" sounds kind of hokey to me. Are there any European
semiconductor companies left?

NXP, STM, Infineon, ARM ring any bells ?

They still make stuff? They sure don't show up on our purchase orders.
Infineon sold their GaAs stuff to Triquint. ARM mostly licenses cores.

We do but older, low density eproms and eeproms from ST.

A mention of NFB might come in handy unless he's looking for 10%+ THD.

I'd imagine the emitter follower he's suggesting will be pretty good,

Not that brilliant. One schematic I saw was no emitter follower.

That must have been the driver.

especially if the pulldown resistor is replaced with a current sink.
It will need a stiff drive, which is why I suggested an opamp.

Which'll probably kill the BC546 ! They're only good for about 625mW @ 25C ambient.

Graham

Quit whining and quit preening and help.

John

 

[John Larkin]

On Wed, 15 Oct 2008 02:24:27 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> 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.

John

 

[John Larkin]

On Tue, 14 Oct 2008 23:48:31 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

mrdarrett@gmail.com wrote:

Say... what *is* your ultimate objective, by the way? If you want a
good (reasonably efficient, relatively cheap, good sound quality,
medium power) solution quickly, you may be happy with the LM3886.
http://www.national.com/mpf/LM/LM3886.html

Guess what's used in the 'gainclone' I recommended he google ?

Graham

He wants to play with discrete components, not just clone a reference
circuit for an IC.

Far too few people even know how to design with transistors and
resistors and capacitors any more. They just connect boxes, or tweak
eval board circuits.

John

 

[Kevin Aylward]

John Larkin wrote:

11. To sequester technical knowledge in journals, defended by
deliberately obscure abstracts, readable at great expense, the revenue
therefrom going to the IEEE, whether the paper turned out to be useful
or not.

John

a.. to accept responsibility in making decisions consistent with the safety,
health and welfare of the public, and to disclose promptly factors that
might endanger the public or the environment;


a.. to avoid real or perceived conflicts of interest whenever possible, and
to disclose them to affected parties when they do exist;


a.. to be honest and realistic in stating claims or estimates based on
available data;


a.. to reject bribery in all its forms;


I guess that rules out aforementioned Bush and co.

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

 

[Kevin Aylward]

Eeyore wrote:

"olivier.scalbert@algosyn.com" wrote:


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

Yes, its a small garden, with horse radish and parsnips, about 1.2m X 1.3M,
that Bode cultivated when he became a vegan.

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

 

[Kevin Aylward]

John Fields wrote:

On Tue, 14 Oct 2008 23:46:50 +0100, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:



John Fields wrote:

Graham, why are you so aggressive with me ?
What is your problem ?

---
I believe both of his parents died when he was very young

Fairly young and was that simply a guess ?
---
No, you mentioned it in one of your earlier posts,
---

But it never made me aggressive.

---
Hogwash.

You may pretend to passivity, but whenever you get a chance you jump
on someone's case and try to shout them down relentlessly.
---

and he's been angry and taking it out on the whole world ever since.

No, I just hate audiophools. They are trying to destroy a once proud
and technically highly competent industry with their claims of
'magic parts' and other pixie dust garbage.

---
You hate a lot more than just "audiophools", buddy-boy.

Just for openers, take a look at your incessant America-bashing.

Weell, they did elect that twat, whats his name.. er... plant, no I mean
bush, as president, so some leeway is due here.

Kevin Aylward (err naturalised us citizen)

www.blonddee.co.uk
www.kevinaylward.co.uk

 

[Kevin Aylward]

Eeyore wrote:

mrdarrett@gmail.com wrote:

Eeyore wrote:
"olivier.scalb...@algosyn.com" wrote:

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.

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

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

Come now Graham, he didn't mention he wants to become an EE... why be
so mean?

Simple facts though and a BC546 is way too tiny to drive a 2N3055.


Olivier, why not try this one?
http://diyaudioprojects.com/Solid/ZCA/ZCA.htm

2SK1058 lateral mosfets can be hard to find however.

Essentially impossible since Hitachi stopped making them. I know a
company in the UK than can provide equivalents though.

That's a truly horrible circuit too.

Indeed, its quite stable though...no need to plant any vegetables.

Kevin Aylward
kevin@kevinaylward.co.uk
www.kevinaylward.co.uk

 

On Oct 14, 12:27 pm, Olivier Scalbert <olivier.scalb...@algosyn.com>
wrote:

mrdarr...@gmail.com wrote:
Say... what *is* your ultimate objective, by the way? If you want a
good (reasonably efficient, relatively cheap, good sound quality,
medium power) solution quickly, you may be happy with the LM3886.
http://www.national.com/mpf/LM/LM3886.html

Best wishes,

Michael

Thanks for the link to the LM3886.

What is my ultimate objective ?
Mmmm, ... difficult question !
;-)

For now, it is having fun.
And for me (and for now) having fun is:
- to be able to build something real that I can touch and listen (I am
building software all day long);
- to experiment with my children;
- to learn something;
- to mix theory and practice;
- to exchange ideas with people;
- listening music on something I have build and designed;
- writing some code to generate different audio waveforms at different
frequencies. I will put them on cd for testing (I have a scope but no
function generator);
- to sniff solder smoke;
- to burn my fingers with hot components (practice the Joule effect);
- ...

I am not interested in buying a new amplifier (I have already a Cyrus)
Or perhaps a Nad C325BEE ...

Olivier

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

 

[John Fields]

On Wed, 15 Oct 2008 18:41:47 GMT, "Kevin Aylward"
<kaExtractThis@kevinaylward.co.uk> wrote:

John Fields wrote:
On Tue, 14 Oct 2008 23:46:50 +0100, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:



John Fields wrote:

Graham, why are you so aggressive with me ?
What is your problem ?

---
I believe both of his parents died when he was very young

Fairly young and was that simply a guess ?
---
No, you mentioned it in one of your earlier posts,
---

But it never made me aggressive.

---
Hogwash.

You may pretend to passivity, but whenever you get a chance you jump
on someone's case and try to shout them down relentlessly.
---

and he's been angry and taking it out on the whole world ever since.

No, I just hate audiophools. They are trying to destroy a once proud
and technically highly competent industry with their claims of
'magic parts' and other pixie dust garbage.

---
You hate a lot more than just "audiophools", buddy-boy.

Just for openers, take a look at your incessant America-bashing.

Weell, they did elect that twat, whats his name.. er... plant, no I mean
bush, as president, so some leeway is due here.

---
Indeed, but then there were those who didn't vote for Bush, and those
who didn't vote at all, but just because we're Americans he tars us all
with his brush-o-hate.
---

Kevin Aylward (err naturalised us citizen)

---
Me too, in a way, but you?

Why???

JF

 

On Oct 15, 11:41 am, "Kevin Aylward"
<kaExtractT...@kevinaylward.co.uk> wrote:

John Larkin wrote:
11. To sequester technical knowledge in journals, defended by
deliberately obscure abstracts, readable at great expense, the revenue
therefrom going to the IEEE, whether the paper turned out to be useful
or not.

John

a.. to accept responsibility in making decisions consistent with the safety,
health and welfare of the public, and to disclose promptly factors that
might endanger the public or the environment;

a.. to avoid real or perceived conflicts of interest whenever possible, and
to disclose them to affected parties when they do exist;

a.. to be honest and realistic in stating claims or estimates based on
available data;

a.. to reject bribery in all its forms;

I guess that rules out aforementioned Bush and co.

Kevin Aylwardwww.blonddee.co.ukwww.kevinaylward.co.uk

Bush, an EE? <vomit>

M

 

[Phil Allison]

"John Larkin"
"Phil Allison"

Agree, but I have no negative supply yet. I have to found or buy or
build
one.



** Consider changing you circuit to include an inductor in place of the
load
resistor - best if you put one in the collector circuit.

Schematic?

** See schem near bottom of page - left click on it to get readable size.

http://www.siliconchip.com.au/cms/A_30859/article.html

This shows a mid 1960s, AWA ( Australian made) all transistor, 12v car
radio.

The 2N301 output transistor ( operating in class A) has an inductor in the
collector circuit, with the speaker wired across it.

Such output stages delivered about 4 watts and had a nice "tone" .



...... Phil

 

[Olivier Scalbert]

Eeyore wrote:

Never even heard of that one. No purpose designed audio op-amp swings rail
to rail btw. If he can provide a negative supply (that eliminates the silly
output coupling cap too) and ensure DC stability he might look at the
venerable but decent TL071/2 etc.

Graham

Hi,
One more question ...
If I remove the output cap, how can I protect my speakers against DC in
case of problem and mistakes? With fuse ?

Olivier

 

[John Larkin]

On Thu, 16 Oct 2008 14:07:05 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

"John Larkin"
"Phil Allison"


Agree, but I have no negative supply yet. I have to found or buy or
build
one.



** Consider changing you circuit to include an inductor in place of the
load
resistor - best if you put one in the collector circuit.

Schematic?


** See schem near bottom of page - left click on it to get readable size.

http://www.siliconchip.com.au/cms/A_30859/article.html

This shows a mid 1960s, AWA ( Australian made) all transistor, 12v car
radio.

The 2N301 output transistor ( operating in class A) has an inductor in the
collector circuit, with the speaker wired across it.

Such output stages delivered about 4 watts and had a nice "tone" .



..... Phil

Oh, that changes things. Oliver proposed an emitter follower, and the
issue I brought up was the limited negative swing associated with the
passive pulldown. This circuit moves the load into the collector, with
no feedback, which increases swing but kills low-end response and
makes Zout very high. And needs a big inductor. Transistors used to be
expensive, so inductors were relatively cheap. No more.

Some big old AM transmitter plate modulators used this inductor-load
config, since it let the RF stage B+ swing from almost ground to twice
the supply voltage. Inefficient as hell, of course, as class A is.
Electricity used to be cheap, too.

I sort of like the emitter follower with an active current sink. It's
simple, AC/DC/thermal stable, and has low Zout and lowish distortion
with no feedback.

John

 

[John Larkin]

On Wed, 15 Oct 2008 18:41:43 GMT, "Kevin Aylward"
<kaExtractThis@kevinaylward.co.uk> wrote:

Eeyore wrote:
"olivier.scalbert@algosyn.com" wrote:


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

Yes, its a small garden, with horse radish and parsnips, about 1.2m X 1.3M,
that Bode cultivated when he became a vegan.

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

Don't be silly. It's where Bode is buried.

John

 

[John Larkin]

On Wed, 15 Oct 2008 10:07:47 -0700 (PDT), mrdarrett@gmail.com wrote:

On Oct 14, 12:27 pm, Olivier Scalbert <olivier.scalb...@algosyn.com
wrote:
mrdarr...@gmail.com wrote:
Say... what *is* your ultimate objective, by the way? If you want a
good (reasonably efficient, relatively cheap, good sound quality,
medium power) solution quickly, you may be happy with the LM3886.
http://www.national.com/mpf/LM/LM3886.html

Best wishes,

Michael

Thanks for the link to the LM3886.

What is my ultimate objective ?
Mmmm, ... difficult question !
;-)

For now, it is having fun.
And for me (and for now) having fun is:
- to be able to build something real that I can touch and listen (I am
building software all day long);
- to experiment with my children;
- to learn something;
- to mix theory and practice;
- to exchange ideas with people;
- listening music on something I have build and designed;
- writing some code to generate different audio waveforms at different
frequencies. I will put them on cd for testing (I have a scope but no
function generator);
- to sniff solder smoke;
- to burn my fingers with hot components (practice the Joule effect);
- ...

I am not interested in buying a new amplifier (I have already a Cyrus)
Or perhaps a Nad C325BEE ...

Olivier



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

Good grief, people keep building minor variations on the same circuit
for, what, 45 years now?

John

 

[John Larkin]

On Thu, 16 Oct 2008 09:00:43 -0700 (PDT), mrdarrett@gmail.com wrote:

On Oct 16, 8:42 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 15 Oct 2008 10:07:47 -0700 (PDT), mrdarr...@gmail.com wrote:
On Oct 14, 12:27 pm, Olivier Scalbert <olivier.scalb...@algosyn.com
wrote:
mrdarr...@gmail.com wrote:
Say... what *is* your ultimate objective, by the way? If you want a
good (reasonably efficient, relatively cheap, good sound quality,
medium power) solution quickly, you may be happy with the LM3886.
http://www.national.com/mpf/LM/LM3886.html

Best wishes,

Michael

Thanks for the link to the LM3886.

What is my ultimate objective ?
Mmmm, ... difficult question !
;-)

For now, it is having fun.
And for me (and for now) having fun is:
- to be able to build something real that I can touch and listen (I am
building software all day long);
- to experiment with my children;
- to learn something;
- to mix theory and practice;
- to exchange ideas with people;
- listening music on something I have build and designed;
- writing some code to generate different audio waveforms at different
frequencies. I will put them on cd for testing (I have a scope but no
function generator);
- to sniff solder smoke;
- to burn my fingers with hot components (practice the Joule effect);
- ...

I am not interested in buying a new amplifier (I have already a Cyrus)
Or perhaps a Nad C325BEE ...

Olivier

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

Good grief, people keep building minor variations on the same circuit
for, what, 45 years now?

John


More like 52 going on 53, looks like...

Oh well, it's either that or Class A...

Or, Heaven forbid, a few new ideas?

John

 

On Oct 16, 12:30 am, Olivier Scalbert <olivier.scalb...@algosyn.com>
wrote:

Eeyore wrote:

Never even heard of that one. No purpose designed audio op-amp swings rail
to rail btw. If he can provide a negative supply (that eliminates the silly
output coupling cap too) and ensure DC stability he might look at the
venerable but decent TL071/2 etc.

Graham

Hi,
One more question ...
If I remove the output cap, how can I protect my speakers against DC in
case of problem and mistakes? With fuse ?

Olivier

Fuse is too slow. You might look into a "current limiting" circuit to
prevent damage also in the case of short-circuiting the output
wires...

Michael