class A amplifier

  • Thread starter olivier.scalbert@algosyn.
  • Start date
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olivier.scalbert@algosyn.

Guest
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
 
<olivier.scalbert@algosyn.com> wrote in message
news:cb07c7ff-4a90-4d6e-b7aa-fa2f172aecf2@t65g2000hsf.googlegroups.com...
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

For a starter, increase C1 to 1000uF. 'T'll get the response down to about
Click to expand...
20Hz.
 
"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 !
Click to expand...
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)
 
On Mon, 13 Oct 2008 06:44:49 -0700 (PDT),
"olivier.scalbert@algosyn.com" <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 !

Thanks very much,

Olivier
Click to expand...
The passive pull-down resistor really limits the negative swing into
the speaker. A constant-current sink would be better.

John
 
Late at night, by candle light, Eeyore
<rabbitsfriendsandrelations@hotmail.com> penned this immortal opus:

"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.

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


Graham (designer of stable pro-audio power amps since 1980)
Click to expand...
Hey, he's having fun, and it's not like it would go into production or
anything.

- YD.
--
Remove HAT if replying by mail.
 
john jardine wrote:
For a starter, increase C1 to 1000uF. 'T'll get the response down to about
20Hz.


Thanks !
Click to expand...
Done.
I will try to find high quality capacitors later ...
 
John Larkin wrote:

The passive pull-down resistor really limits the negative swing into
the speaker. A constant-current sink would be better.

John
Click to expand...
Ok, I will try it.
Thanks.
 
On Tue, 14 Oct 2008 01:59:14 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

"olivier.scalbert@algosyn.com" wrote:
Click to expand...
..
..
..

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)
Click to expand...
---
Mean Mister Mustard sleeps in the park
Shaves in the dark trying to save paper
Sleeps in a hole in the road
Saving up to buy some clothes
Keeps a ten-bob note up his nose
Such a mean old man
Such a mean old man

His sister Pam works in a shop
She never stops, she's a go-getter
Takes him out to look at the queen
Only place that he's ever been
Always shouts out something obscene
Such a dirty old man
Such a dirty old man

Mean Mister Mustard
Such a dirty dirty
Mean Mister Mustard
Such a dirty dirty
Mean Mister Mustard

Mean Mister Mustard sleeps in the park
Shaves in the dark trying to save paper
Sleeps in a hole in the road
Saving up to buy some clothes
Keeps a ten-bob note up his nose
Such a mean old man
Such a mean old man

JF
 
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?
Click to expand...
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.
Click to expand...
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.

Graham
 
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 ...
Click to expand...
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)
 
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)
Click to expand...
Graham, why are you so aggressive with me ?
What is your problem ?

I have read it in Farnell catalog.

Olivier
 
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)
Click to expand...
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".

Olivier
 
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
Click to expand...
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
 
On Tue, 14 Oct 2008 17:13:05 +0200, Olivier Scalbert
<olivier.scalbert@algosyn.com> 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, ...

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".

Olivier
Click to expand...

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
 
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 ... !
Click to expand...

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

Olivier
 
On Tue, 14 Oct 2008 14:39:31 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

John Fields wrote:



Just simple facts John.

Graham
Click to expand...
---
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
 
On Tue, 14 Oct 2008 16:57:37 +0200, Olivier Scalbert
<olivier.scalbert@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 ?
Click to expand...
---
I believe both of his parents died when he was very young and he's been
angry and taking it out on the whole world ever since.

JF
 
On Tue, 14 Oct 2008 14:44:39 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> 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.
Click to expand...
---
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 ?
Click to expand...
---
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)
Click to expand...
---
Not something I'd boast about, if I were you...

JF
 
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
Click to expand...
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 !

Olivier
 
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