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Old 22nd November 2009, 08:40 PM   #1
olof102 is offline olof102  Sweden
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Default 5W Class A transistorized amp

Hi,

I'm considering building this amp: DIY 5 Watt Class-A Audio Amplifier Circuit Behaves Valve Amp | Electronic and Techno

But I can't find the BD439 transistors, so my question to you guys is, would it work with BD441 or BD442?

By the way, have anyone tried this amp? how does it sound? I know it's cheap, so I'm not expecting it to be a miracle. I've only built a gainclone TDA2050 before, can it be compared to that one?

Cheers
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Old 22nd November 2009, 11:21 PM   #2
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Default I have built both..and the TDA2030 sounded better

I suppose the TDA2050 would sound the same as the TDA2030...but really i have never assembled the TDA2050.

This amplifier needed modifications to operate with other transistors, different than he ones suggested.... i do not remember exaclty, as this happened long time ago, but i remember was not very good and gave me some bad time to put the one to operate.

The sound resulted not very good when i have finished...was dismounted alike other thousands i have assembled by curiosity to listen...the ethernal search for a miracle amplifier....and i continue to do that....i have not find the perfect one.

All them have qualities and all them have weak points.

I do not suggest you to assemble..keep you TDA2050 because, for sure, you will be more happy this way.

I will not feed this thread... chip amplifiers is another forum..so... this post is the first and the last.... of course the amplifier you asked is solid state, discrete and transistorized, but the option is a chip amplifier.

Read our forum a little bit more, there are several better options than this amplifier...take some time to read and to know people and designs we have into this forum and also into the Chip amplifiers forum, also Nelson Pass.... study first (compare, judge, ballance,select, weigth, think about and decide latter, for sure will not be this one you have posted)....then, after that study, you will decide (better) what to be assembled.

Will be interesting if you have the kindness to complete your profile, informing your country for instance... it is nice to make a presentation about you, we like to know forum friends.

regards,

Carlos
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Last edited by destroyer X; 22nd November 2009 at 11:28 PM.
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Old 23rd November 2009, 01:39 AM   #3
djk is offline djk
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The circuit is attempting to dynamic bias Q2.

I think R8 and R9 would have to be hand selected for different gain variations in Q2.

This type of circuit is sensitive to power supply quality too. Pehaps you should look at the Zen v4 from Nelson Pass. It has a proberly designed dynamic bias, and a supply regulator. The N-channel FETs may be any type you can obtain locally, Q3 may be any small signal NPN device.

http://passdiy.com/pdf/zen-v4.pdf
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Old 23rd November 2009, 03:17 AM   #4
Bigun is offline Bigun  Canada
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I agree with what Carlos said.

And he's being very modest - he has a nice design worth looking at called the DX amplifier. Greg's Web Site

Also look here: ESP Projects Pages - DIY Audio and Electronics


Olof - a name from the North, from cold places ?

p.s. for the Class A amplifiers:http://www.tcaas.btinternet.co.uk/index.htm

and also: http://www.passdiy.com/articles.htm


These will keep you busy, lots of very useful stuff.
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Last edited by Bigun; 23rd November 2009 at 03:19 AM.
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Old 23rd November 2009, 06:11 AM   #5
godfrey is offline godfrey  South Africa
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JLH's 1969 amp is almost as simple (4 transistors), and probably a lot better. Details here: The Class-A Amplifier Site
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Old 23rd November 2009, 06:22 AM   #6
ratza is offline ratza  Romania
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I liked a lot this one:
DIY Class-A 2SK1058 MOSFET Amplifier Project
The biggest problem is the power supply, you'll need plenty capacitors. As I wasn't able to get rid of the hum completely, I built a capacitance multiplier at the cost of another heatsink.
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Old 23rd November 2009, 06:35 AM   #7
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Quote:
Originally Posted by ratza View Post
I liked a lot this one:
DIY Class-A 2SK1058 MOSFET Amplifier Project
The biggest problem is the power supply, you'll need plenty capacitors. As I wasn't able to get rid of the hum completely, I built a capacitance multiplier at the cost of another heatsink.
Hey Ratza,

That amp will not give you over 1W at 10% THD. But you can easily rebuild it to a Zen V.1 to get proper function at the expense of lower sensitivity and Zin. With a CCS on top as in the Zen you will also get a lot better PSRR.
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Old 23rd November 2009, 06:50 AM   #8
ratza is offline ratza  Romania
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I know. I only built it for fun and to "see" how it sounds when compared side by side with a tube (EL84 single ended). Nevertheless, I really liked it's sound but it's not the kind of amplifier which I would enjoy every day.
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Old 23rd November 2009, 07:30 AM   #9
Mooly is offline Mooly  United Kingdom
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Raher than the original circuit in post #1 you may as well try something like this which is infinitely better and no more complex,
The Class-A Amplifier Site

First item... the JLH amp
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Old 23rd November 2009, 11:19 AM   #10
olof102 is offline olof102  Sweden
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First of all, thank you very much for all answers. I've looked into all of the links and apparently the transistors aren't able to get at my local electronic store (https://www1.elfa.se/elfa~eu_en/b2b/...do?tab=catalog).

Anyway, I found another circuit on the web: Cheap 100 to 150 Watt Amp . It seems really easy and cheap to build, so I think it would suit me perfectly.

Is there anyone that has tried this one? or how do you think it will perform?

Thanks,
Olof (Yupp, south. Sweden.)
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