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Old 9th October 2003, 10:14 AM   #1
morBin is offline morBin  Italy
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Default 50W Class AB BJT suggestions for newbie

Hi fellows, I want to build my first amp and think a 50W Class AB all in BJT would suit fine (less heat and power consumption). I'm looking for a good quality project rather than a cheap one.
I already have an idea for the psu part (see image)

Any suggestions about the circuit?
Any link I can go take a look at?

Thnx ya'll
morBin
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Old 9th October 2003, 11:43 AM   #2
mik is offline mik
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http://sound.westhost.com/project3a.htm
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Old 9th October 2003, 02:08 PM   #3
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Morbin,

The Aksa 55 watt kitset amplifier is a truly marvelous product.

http://www.printedelectronics.com/pr.../products.html

All bipolar and runs cool as a cucumber.....
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Old 12th October 2003, 01:09 PM   #4
morBin is offline morBin  Italy
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thanks mik, pmkap

I found lots of stuff about the AKSA and I think I'll stick with this one.

c'ya
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Old 12th October 2003, 08:12 PM   #5
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Thumbs up Newbie Amp

I Built this amp about milion times...it is not the best sounding amplifier....but it works realy fine... It is base schematic, it has some obsolete components tha can be raplacet with some newer... It also can be upgraded in many ways but i will leave that to you I also have PCBoards and all the rest...
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Old 12th October 2003, 09:29 PM   #6
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being someone who started on citation 12, I would suggest that you do one of those: it is very much like P3A but without an emitter follower stage. the schematics is pretty easy to find.

I have been testing a mosfet version of it for some time now, only in simulation tho. since you had asked for an all bjt design, I replaced the mosfets with mje15030/1 and ran it through my simulator. It worked quite well: 0.017% thd at 20khz full power into 8ohm, and 0.011% thd at 1khz. for 4ohm, it delivers 0.067% at 20khz and 1khz.

I will post the schematics later if you want.
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Old 12th October 2003, 09:33 PM   #7
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Default Re: Newbie Amp

Quote:
Originally posted by Drafance007
I Built this amp about milion times...

it is quite simple but may need some tweaking:

1) one can do with a full complementry OPS now.
2) I would float the 220 resistor on the emittor of T5;
3) one may want to change the 2k2 resistor on T1's collector so that the current going through T1 and T2 is roughtly the same. a 1K resistor will do that.

I thought using diodes for biasing purposes is quite simple but I haven't tried it in any real amp. Has anyone done that?
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Old 12th October 2003, 10:11 PM   #8
morBin is offline morBin  Italy
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Thanks Drafance.

Well, this amp comes from a project of yours?
How much money would it take to fix it up?
Output RMS power?

Why would you suggest me this one instead of AKSA or the "3a"?

morBin
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Old 12th October 2003, 11:21 PM   #9
morBin is offline morBin  Italy
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Hey Millwood I appreciate that!
Post the schematics please.
The THD looks good to me, but to be sure on how it sounds, one should build it and listen to it, right?
This is my first amp, but I want to last it a long while!! (quality listenings I mean)

I'm quite new into amp diy, but I'd like to know as much stuff as I can before deciding for my best pal.

morBin
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Old 13th October 2003, 12:40 AM   #10
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Default Newie Project

There is no reason why this amp. It is very regular conception amplifier... Citation 12 is superior than this amp. Also many other. It is your choice. I was given this schematic a long time ago when i wanted to build simple but functional amplifier, so i guess maybe you would be intrested.
I didn't realy ever measure power of this amp, but i think that it can give about 50-60w rms on 4 ohm load with less than 1% thd.

The modifications that were sugested by -millwood- would be fine for this amp. There are also some other but the amp would be much complicated after.

You can build this thing with anything that you have in house...it will still work. I tryed for output transistors many stuff, even 2n3055, BD249, BD243C... It is realy cheap... Power supply may cost you samo money and cooling...all the rest is cheap.
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