Another amp

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If nothing is burning then you have made some connection error. Check the board for bad soldering. I had case where one resistors pin was not soldered very good 🙂

For output transistors i thought to use BD911/912 (3 pairs) because of fake MJ's! 😡
I have made amplifier with those BD's and made some nasty torture for the amp. I have driven it with 18 volts pure sine, which is 40wats for 8 ohm speaker. Nothing burned out. After this i think BD's were originals, fake ones will not survive something like that, i guess :xeye:
 
I believe that i have found one error on your board. On picture you can see that one transistors is reversed.
 

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heY !!!! Thanks mate...you are right...
i didnt get time to look at it but you got it pal..

I had blown one od that transistor...and replace it ...i think it must have blown up again ...will have to replace ...
will update as soon as i get the new transitore in.

Thanks again.
 
You're welcome! 😉

I had also situation like that some years ago. But, you live, you learn.... 🙂

Yesterday i was working on my second heat sink for other channel. I have bought some Mospec Mj's but i think they are also fake ones. I don't know how does the original prints look like on Mospec. Well, i just hope that it will work.
Two pairs per channel for some 130 w at 8 ohms will do just fine.

I had also 130w amplifier at 8 ohm with just one pair of fake BD317/318 and it worked very, very nice. It was pupmping the power like blast and did not blew out :xeye:
 
Here it is! I have tested the amp.
Sound is ok, nice. One thing has scared me for a little bit. Almost at full power it had nasty sound, both channels. I believe that it is because of VI limiter in amplifier. Is there any chance to fix this beside turning it off?
 
Testing done

Hey guys testing done...
had some wrongly placed resistors (Value)
Replaced them and am really iimpressed with the quality of sound.
I mean me and friend were expecting some hum or hiss but 0 distortion 0 hum...plays rock on..

But am not happy with the power that its giving me at full level.
I tested it on my ZUNE and Sony erricson phone, its not as loud as i expected....what do you say guys...i need more power...
But AMP desgin is rock solid...

My PCB's are 100% perfect no mistake in the track work at all...
 
What do you beam by full level? 😕

The amplifier is rated 250w at 4 ohm and about half for 8 ohm.
If you have 8 ohm speaker then the amplifier has something about 125wats.
Do you get distortion at lover level?
Does your preamplifier has enough output to drive the amp at full level?
 
Thats what i said...am just using the phone and other music players to test
When i say full level i mean the full voluome of the Music players...this thing doesnt have volume control..
And no noise..no hum nothin..its dead silent...thats what i like the most..
 
One question.

My transformer is rated 40-0-40 at 7 amps, so power = 280 Watts.
This looks fine for getting 125 watts at 8 ohms, do i have to have a higher rated transformer if wanna drive 4 ohms load ??

Will i need a 40-0-40 at 12 amps approx ???
 
Your transformer is 40-0-40 and 7 Amps? Then it is not 280VA it is actually 560VA 🙂 Because it is 80v x 7a=560VA which is enough for 2 channel at 125w at 8 ohm speaker.
For 4 ohm speaker, that is 250w, you will need minimum 750VA with 40-0-40v for stereo.
 
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