class A amplifier

On Oct 14, 8:18 am, Olivier Scalbert <olivier.scalb...@algosyn.com>
wrote:

mrdarr...@gmail.com wrote:

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

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

2SK1058 lateral mosfets can be hard to find however.

Michael

Thanks for the link Michael.
I do not want to become EE !
At least good EEs should respect IEEE Code of Ethics (point 5).http://www.ieee.org/portal/pages/iportals/aboutus/ethics/code.html

;-)

Olivier

Oh that's good to know.

And to think, some people will sell amplifiers out of a van, with
horrible distortion, that can even destroy your speakers...

http://en.wikipedia.org/wiki/White_van_speakers

Michael

 

On Oct 14, 7:57 am, Olivier Scalbert <olivier.scalb...@algosyn.com>
wrote:

Eeyore wrote:

Olivier Scalbert wrote:

john jardine wrote:
For a starter, increase C1 to 1000uF. 'T'll get the response down to about
20Hz.

Thanks !
Done.
I will try to find high quality capacitors later ...

The 'quality' of capaciors is an entire irrelevance with something so primitive.
In fact it's almost a complete irrelevance completely unless you buy Asian junk.

I take it you've been 'Audiophooled' by reading magazines written by wholesale
fraudsters. Audiophile was it ?

Graham (pro-audio designer since 1971)

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

I have read it in Farnell catalog.

Olivier

Oh, don't mind Graham, he's still working up the courage to ask a girl
out for drinks.
http://groups.google.com/group/sci.electronics.design/browse_frm/thread/b2d00e347e5ddd6a?scoring=d&

He does know his audio stuff though.

Welcome to Usenet.

Michael

 

[John Fields]

On Tue, 14 Oct 2008 18:54:57 +0200, Olivier Scalbert
<olivier.scalbert@algosyn.com> wrote:

John Fields wrote:

---
Since John Jardine suggested that he increase the _capacitance_ of C1 to
1000ľF, I'm sure Olivier took that to mean the capacitor would be higher
quality since it would extend the audio response of the amp down to
about 20Hz.

He's already said he's a newbie and just starting out, so why do you
beating him up instead of showing him the right way to do it?

Because you're a real shit, that's why.
---

I take it you've been 'Audiophooled' by reading magazines written by wholesale
fraudsters. Audiophile was it ?

---
And you were never taken in by wholesale fraudsters, ever, because
you've always been able to see through the smoke screens?
---

Graham (pro-audio designer since 1971)

---
Not something I'd boast about, if I were you...

JF

It is not exactly what I mean.
Of course increasing value of C1 will increase the low frequency response.
Problem, I have not 1000ľF at home, I have used 2 500ľF in parallel ...

And as I have no good electronic shop near my home, I generally buy my
components at Farnell.
By looking inside the 2006 edition, I have discovered page 936 the ECA
audio caps from Panasonic.
"High fidelity, low distorsion, High resolution, ...."

That is why I will buy these ones !

---
In this case, then, I'm afraid that Graham is right since the audible
output of your circuit will hardly be improved by the use of "High
fidelity, low distorsion, High resolution, ...." capacitors.


JF

 

On Oct 13, 6:44 am, "olivier.scalb...@algosyn.com"
<olivier.scalb...@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 !

Thanks very much,

Olivier

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

 

[Olivier Scalbert]

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

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

 

[Olivier Scalbert]

John Fields wrote:

In this case, then, I'm afraid that Graham is right since the audible
output of your circuit will hardly be improved by the use of "High
fidelity, low distorsion, High resolution, ...." capacitors.


JF

Ok, I will buy "normal" capacitors.

Olivier

 

[John Larkin]

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

 

On Oct 14, 11:59 am, John Fields <jfie...@austininstruments.com>
wrote:

On Tue, 14 Oct 2008 18:54:57 +0200, Olivier Scalbert



olivier.scalb...@algosyn.com> wrote:
John Fields wrote:

---
Since John Jardine suggested that he increase the _capacitance_ of C1 to
1000ľF, I'm sure Olivier took that to mean the capacitor would be higher
quality since it would extend the audio response of the amp down to
about 20Hz.

He's already said he's a newbie and just starting out, so why do you
beating him up instead of showing him the right way to do it?

Because you're a real shit, that's why.
---

I take it you've been 'Audiophooled' by reading magazines written by wholesale
fraudsters. Audiophile was it ?

---
And you were never taken in by wholesale fraudsters, ever, because
you've always been able to see through the smoke screens?
---

Graham (pro-audio designer since 1971)

---
Not something I'd boast about, if I were you...

JF

It is not exactly what I mean.
Of course increasing value of C1 will increase the low frequency response.
Problem, I have not 1000ľF at home, I have used 2 500ľF in parallel ....

And as I have no good electronic shop near my home, I generally buy my
components at Farnell.
By looking inside the 2006 edition, I have discovered page 936 the ECA
audio caps from Panasonic.
"High fidelity, low distorsion, High resolution, ...."

That is why I will buy these ones !

---
In this case, then, I'm afraid that Graham is right since the audible
output of your circuit will hardly be improved by the use of "High
fidelity, low distorsion, High resolution, ...." capacitors.

JF

Just as long as they're large enough, and don't suffer from Capacitor
Plague...

M

 

[john jardine]

"Olivier Scalbert" <olivier.scalbert@algosyn.com> wrote in message
news:48f4f26a$0$2858$ba620e4c@news.skynet.be...

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

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

A beautiful description. It's what drives me as well. If something is not
enjoyable, then through choice it should not be pursued.
I sometimes get the feeling that many professionals (of all callings!) are
born with their boots on, (a local expression) hence never need to pass
through a learning phase .

 

[Rich Grise]

On Mon, 13 Oct 2008 06:44:49 -0700, olivier.scalbert@algosyn.com wrote:

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

I'd do it different, but basically it's right out of the book. Unless
you have to adjust the bias periodically, I'd pick an operating point
and use a fixed resistor for R3, then put the left side of C2 to the
wiper of the volume control pot (in ampli1).

The preamp is pretty much standard; there's no problem with the
volume control, depending on the signal level you're dealing with.

As I suggested above, move the volume control to the input side of
the power amp, and run the preamp full-bore all the time - just design
the circuit so that you get "line out" (about 1VRMS) for your maximum
expected input.

And as far as C4 & R8 (preamp1), you're already ahead of me on that
one. ;-)

Cheers!
Rich

 

[Rich Grise]

On Tue, 14 Oct 2008 18:54:57 +0200, Olivier Scalbert wrote:

"High fidelity, low distorsion, High resolution, ...."

That is why I will buy these ones !

This is probably foolish; you'd be paying extra for the marketing bype.

In that application, just get the cheapest electrolytics they have.

Cheers!
Rich

 

[Rich Grise]

On Tue, 14 Oct 2008 01:59:14 +0100, 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.

Thanks,
Rich

 

[Eeyore]

Olivier Scalbert wrote:

mrdarrett@gmail.com wrote:

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

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

2SK1058 lateral mosfets can be hard to find however.

Michael

Thanks for the link Michael.
I do not want to become EE !
At least good EEs should respect IEEE Code of Ethics (point 5).
http://www.ieee.org/portal/pages/iportals/aboutus/ethics/code.html

I agree with it totally. To ecourage you to build shitty circuits would be
grossly negligent.

If you want to learn about audio amplifiers, some excellent resources can
be found here ....
http://www.dself.dsl.pipex.com/ampins/ampins.htm

Graham

 

[Eeyore]

John Fields wrote:

Eeyore wrote:
John Fields wrote:

Just simple facts John.

Graham

---
You're a goddam liar.

You know very well that this is seb and that instead of just putting the
guy down by puffing yourself up as an "expert" (implying that he's a
virtual nonentity) you should be helping him understand where his
deficiencies lie, like Larkin did.

But no, you always have to try to make yourself feel important by trying
to make it seem like everyone is less important.

JF

I have given him a link to a far far better site.
http://www.dself.dsl.pipex.com/ampins/ampins.htm

Graham

 

[Eeyore]

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.

Graham

 

[Eeyore]

Olivier Scalbert wrote:

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, ...

Well that's good but dare I say you missed out on the practical lab work ?

Take a look at this will you. He's another good amp designer too.
http://www.dself.dsl.pipex.com/ampins/ampins.htm

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".

I hate to see people waste their time walking down blind alleys.

Graham

 

[Eeyore]

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 ?

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

Graham

 

[Eeyore]

Olivier Scalbert 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?

egos ... !

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

It'll work but I haven't seen 741s used in decent audio at all and in
indifferent audio only since about 1980.

What is it you're really trying to do and what's its purpose ? Then I may
be able to actually really help you somewhat.

Graham

 

[Eeyore]

John Larkin wrote:

Olivier Scalbert 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?

egos ... !

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

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.

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

 

[Bret]

On Tue, 14 Oct 2008 23:08:51 +0100, Eeyore wrote:

Olivier Scalbert wrote:

mrdarrett@gmail.com wrote:

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

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

2SK1058 lateral mosfets can be hard to find however.

Michael

Thanks for the link Michael.
I do not want to become EE !
At least good EEs should respect IEEE Code of Ethics (point 5).
http://www.ieee.org/portal/pages/iportals/aboutus/ethics/code.html

I agree with it totally. To ecourage you to build shitty circuits would be
grossly negligent.

If you want to learn about audio amplifiers, some excellent resources can
be found here ....
http://www.dself.dsl.pipex.com/ampins/ampins.htm

Graham

What about point 7 ?