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-   -   Low power amplifier (http://www.diyaudio.com/forums/solid-state/193877-low-power-amplifier.html)

MarianB 2nd August 2011 03:13 PM

Low power amplifier
 
Greetings.

I'm in need of a simple low power amplifier, preferably with bipolar transistors ( complementary or not ), something between 30 and 50W on 4Ohm speaker, simple or duble power suply, it needs to be made with easy to find transistors, and not verry expensive, i need to built an amplifier like this for someone and i thougt here would be best to search, the net is full of things like that, yes, but not all of them are ok, and knowing here are many experts in the field i need youre advice in this matter, so any imput would be greatly appreciated.

Best wishes to all, Marian.

alexcp 2nd August 2011 04:29 PM

Try a kit from AmpsLAB.

digits 2nd August 2011 04:49 PM

Original DX, less than $10 in parts per channel, single output pair of what have you, will do even 100W into 4A.

MarianB 2nd August 2011 05:13 PM

Maybe i didn't express my self properly so i apologise, what i need is an schematic of the cind of amplifier i have described in the first post here, i will buit the amp, i will desighn the PCB then make it on PNP method, i will do all the work there is on the amp, i just need a good schematic, one that someone had made it and was happy with it, so can anyone help me on that?

lineup 2nd August 2011 05:22 PM

Have a look at some power amplifier projects by Rod Elliott.
They have schematics and low cost parts.
ESP Projects Pages - DIY Audio and Electronics

Maybe this fit your request : http://sound.westhost.com/project3a.htm

MarianB 2nd August 2011 05:33 PM

ESP was my first choice when i have searched, but MJL21193 it's not cheap at all, in fact it costs more than the mosfet's of my high power amplifier so it is not cost efective, as i see it may be possible to change it with BD911/BD912, the same cind of devices but with lower ratings such as max voltage, max current and so on, so am i wright, can it be change with what i sayd?

AndrewT 2nd August 2011 05:34 PM

The original DX, it was guaranteed by the designer.
Or try the latest DX or any of the twenty seven variations that came in between, all but one of which, were guaranteed by the designer.

25W into 4r0 requires 14Vpk and 3.5Apk.
50W into 4r0 requires 20Vpk and 5Apk.
These can be met by single pair output stage powered by a 18+18Vac or 25+25Vac 160VA transformer.

The most expensive parts will be the chassis, the next most expensive will be the transformer.
Replacing an amplifier because it blew up, or was a bad choice, is likely to add no more than 10% to your budget.

Elvee 3rd August 2011 07:48 AM

Quote:

Originally Posted by MarianB (Post 2658310)
Greetings.

I'm in need of a simple low power amplifier, preferably with bipolar transistors ( complementary or not ), something between 30 and 50W on 4Ohm speaker, simple or duble power suply, it needs to be made with easy to find transistors, and not verry expensive,

The Circlophone fits the bill exactly:
http://www.diyaudio.com/forums/solid...rclophone.html
Compared to other low-cost designs, it is adjustment-free, requires no thermal compensation, is thermally stable, and offers better quality and performances.
It is happy with any parts, requires no selection or pairing, and runs on identical output transistors rather than complementary: the OP devices can be 2N3055 or similarly cheap transistors.

The PCB designed by Wakibaki has been tried and validated by odysseybmx414.

forr 3rd August 2011 09:29 AM

Mike Renardson's amp very detailed project is worth having a look :
MJR7-Mk5 Mosfet Power Amplifier

frederic75 3rd August 2011 10:57 AM

Hi,
Bipolar, low power, not expensive, easy available components...
I suggest a push pull 2N3055 !
this one for example :
http://78.229.172.208/ELEX/ARTICLES_...PLI-AUROCK.pdf


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