Prev: cascading two dc/dc regulator
Next: how to get this PWM DC motor control to handle more power
From: YD on 14 Oct 2008 08:32
Late at night, by candle light, Eeyore
<rabbitsfriendsandrelations(a)hotmail.com> penned this immortal opus:

>
>
>"olivier.scalbert(a)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)

Hey, he's having fun, and it's not like it would go into production or
anything.

- YD.
--
Remove HAT if replying by mail.
From: Olivier Scalbert on 14 Oct 2008 09:08
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 ...
From: Olivier Scalbert on 14 Oct 2008 09:12
John Larkin wrote:

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

Ok, I will try it.
Thanks.
From: John Fields on 14 Oct 2008 09:34
On Tue, 14 Oct 2008 01:59:14 +0100, Eeyore
<rabbitsfriendsandrelations(a)hotmail.com> wrote:

>
>
>"olivier.scalbert(a)algosyn.com" wrote:

..
..
..

>> 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)

---
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
From: Eeyore on 14 Oct 2008 09:38


mrdarrett(a)gmail.com wrote:

> Eeyore wrote:
> > "olivier.scalb...(a)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.

Graham

First  |  Prev  |  Next  |  Last
Pages: 1 2 3 4 5
Prev: cascading two dc/dc regulator
Next: how to get this PWM DC motor control to handle more power