Stereo Audio power amplifier 2 x 40W - 80W

[faizanbrohi]

No i am actually making two complete units with common input right , amd i am using  4 ohms speakers .

 

[audioguru2]

That is an awful lot of power. What is it for?

 

[faizanbrohi]

IT is to make Power Amplifier System with a CD Player and temprature display , 10 band VU meter and things like that.ok

 

[audioguru2]

Be careful you don't go deaf.
Many speakers have a sensitivity of 90dB/1W/1m. 250W in them produces a sound level of a whopping 114dB at a distance of 1m and 117dB if two speakers are playing. Much too loud.

 

[faizanbrohi]

But the amplfiers that are in the market , especially Car Audio Amplfiers , are rated 1000W maximum value and 500W x 2 channel RMS

IF i use one 250W for the Deck and the other one for the Car . i Will have to use a square wave inverter to produce 300W from a 12V car battery. and a square wave is easily converted to DC .

 

[audioguru2]

The inverters in high power car amplifiers operate at about 65kHz and use Mosfets. Then the transformer and filter caps can be tiny.
http://www.sound.westhost.com/project89.htm

 

[faizanbrohi]

There is one problem , the output is only 35 and -35V , i neeed 55 and -55V

 

[audioguru2]

The turns ratio of the transformer determines its output voltage. Then you will need heavier wire for everything and an extra pair of Mosfets for the higher power.

 

[faizanbrohi]

I can use MJ15024 in this configration , they are 250W power transistors , to increase power , beacuse MTP75N06 is not manufactured as well as MTP60N06
THis only Leave BUZ11 and IRF540 , which can be found . but if i use MJ15024 in parallel combination with a good heatsink will it work

Can You tell be a more simpler method , how i can order a transformer with input ratings and output ratings . so it is easy. (ie input voltage , centre tapped , output input current)

 

[audioguru2]

The M250 amplifier is supposed to use four MJ15024 power transistors and four MJ15025 power transistors.

A power transformer needs a primary AC voltage rating the same as your mains (240VAC, 230VAC, 120VAC) and for a stereo amplifier with 250W from each channel the secondary would be 80VAC centertapped, 8A which is also written as 40VAC-0V-40VAC, 8A. It will give positive and negative 54.5VDC at 5.7A.

 

[faizanbrohi]

I think you are mistaken , i am talking about the Inverter That you send .. ;D

 

[audioguru2]

The SMPS for a car amplifier that I posted operates at about 65kHz so it uses extremely fast Mosfets. Transistors are much too slow for the high frequency. The article mentions the IRF540 Mosfet which is very common, and hundreds of other suitable Mosfets are available.

The article says how to make the transformer, changing the number of turns for its secondary to get the voltage output that is desired. I haven't seen high frequency, high power transformers like this for sale anywhere.

 

[faizanbrohi]

Actually it seems like i have to make a toriodal transformer which it says about 4cm Dia , Isn't there any simpler schematic please for god sake..

 

[audioguru2]

Isn't there any simpler schematic

You could make a simple low-frequency inverter with an ordinary huge and heavy power transformer.

 

[faizanbrohi]

As the Site says

'' A good starting point is using 4 turns for each primary (that is, 4 turns, centre tap and another 4 turns IN THE SAME DIRECTION). To calculate the number of turns of the secondary winding, multiply by the turns ratio. For example, if you want to build a +/-30V supply, the turns ratio is 30/13.8=2.2 approx, so wind 2.2 x 4 = 8.8 turns (better 9 turns, to overcome the diode losses) for each secondary (that is, again, 9 turns, centre tap and another 9 turns IN THE SAME DIRECTION). ''

And

''Another possibility is using a toroid. You can extract it from a BIG power inductor. As a guide, a 4cm diameter toroid with a section of about 1cm2 can be used for a > 250W SMPS. Winding is a little bit more complicated than with ETD cores but with a little practice is not too difficult either.''

Now

THe Idea is we can use it to make a >250W power supply using 4cm toriod and some wires. For my Output i would require

55/13.8 = 3.98 which is 4 turns and 4 x 4 = 16 turns . the problem is do i require a biggger toriod than the 4cm one ? If yes how big.

 

[audioguru2]

His power supply makes about half the power you need. So maybe the core for the torroid should be bigger so it doesn't saturate, and use thicker wire to handle the higher current.

 

[faizanbrohi]

I think about 6 to 7cm toriod but be fine and 20SWG Wire gauge would be adequate , what abou u

 

[audioguru2]

I think about 6 to 7cm toriod but be fine and 20SWG Wire gauge would be adequate , what abou u

The torroid will be good if you can find one, but 20 guage wire is too small for the primary winding, even if you parallel 6 strands. The max current will be about 62A in the primary.

 

[faizanbrohi]

So how muc gauge do i need any idea . 12 or 10 maybe.

 

[audioguru2]

You were close before. 20 gauge wire can carry nearly 10A so 6 pieces of 18 gauge in parallel will be fine for the primary.