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Old 2nd August 2006, 09:46 AM   #51
Did it Himself
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Bridge amps work best with one transformer. At the very least you need to make sure both amps share a good ground if you use two transformers.
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Old 4th August 2006, 05:17 AM   #52
myanmar is offline myanmar  Myanmar
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Hello richie00boy,

Quote:
That amp will blow up after time because it has no thermal compensation.
Is there any other (above 100W AMP) without thermal compensation ?

I don't understand
My AMP is in stable state without thermal compensation, Why?
Now, I already tested my bridge AMP without Fan 3~4hours with two parallel 8 ohm SPKs above 100W output condition.
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Old 4th August 2006, 10:56 AM   #53
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Quote:
Originally posted by myanmar
Hello richie00boy,

Is there any other (above 100W AMP) without thermal compensation ?
Not any good ones.

Quote:
Originally posted by myanmar
I don't understand
My AMP is in stable state without thermal compensation, Why?
Now, I already tested my bridge AMP without Fan 3~4hours with two parallel 8 ohm SPKs above 100W output condition.
Then you have been lucky... so far.
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Old 12th August 2006, 05:36 AM   #54
myanmar is offline myanmar  Myanmar
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Old 15th November 2006, 04:57 AM   #55
myanmar is offline myanmar  Myanmar
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hello friends,

Now.
I want to use two rail supply.
that is +/- 80V & +/- 40V use in my that bridge amp.
+/- 80 V supply only for mosfet & +/- 40V supply for the rest.

Can I use two rail supply in my bridge AMP ?


Another one is that can use as Class G ( use relay )?


Pls, Advice & reply.

I want to test that.
What will happen & carful when I test ?

Here is my circuit diagram.
http://www.diyaudio.com/forums/attac...amp=1149693177

Regards.
Myanmar
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Old 15th November 2006, 11:57 AM   #56
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I don't understand why you want two rails like that, as you say you want to try class-g as well. You would either use class-g or just have one set of rails usually. Sometimes you have slightly higher rails for driver stage, but not the other way round.
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Old 15th November 2006, 02:27 PM   #57
ilimzn is offline ilimzn  Croatia
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One pair of IRF540/9540 can do 100W into 4 ohms as long as the 4 ohms are not too reactive, and the transistors are VERY well cooled. IRFP240/9240 can do the same but with far less restrictions as their case alowes a lot more power dissipation. They are also slightly more linear. An even better combination is IRFP9140 and IRFP240 for reasons i have mentioned about 10 times on this forum.
+-50V rails are the absolute maximum limit for 540/9540. For more than that you need 640/9640, but you will need 2 pairs per amplifier. It would be a better idea to use a slightly higher rail voltage for the driver stage (about 5V higher) to get extra power and reduce heat.
The schematic shows no thermal compensation. Some can be achieved by mounting two of the driver stage transistors on the heatsink. The reason why this amp may not self destruct (but bias will not be thermally stable by any means!) are the source resistors. I know i would never use the amp this way.
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Old 15th November 2006, 08:52 PM   #58
MikeB is offline MikeB  Germany
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Quote:
Originally posted by ilimzn
An even better combination is IRFP9140 and IRFP240 for reasons i have mentioned about 10 times on this forum.
I don't think so, it was at least a 100 times...

BTW, what do you think about the combination IRFP9240 to IRFP340 ?

Mike
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Old 16th November 2006, 12:50 PM   #59
myanmar is offline myanmar  Myanmar
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Thanks for reply & advice.

I want more power.

I want to know is
IRF540 is 100 V in data sheet.
So IRF540&IRF9540 will 200V.
Is that true ?
Can I put +/- 80 V rail for mosfet ?
May that be over current ?

What will be main problem in my circuit ?
Need many MOSFET for parallel ?

( IRF 540 x 2 ) & IRFP240
Which is more power & more stable ?
Because I want to compare for price.
IRFP240 is tribble than IRF540 in my country.

Regards,
Myanmar
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Old 16th November 2006, 01:12 PM   #60
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IRF540 is 100V so you cannot have more than 100V total across all rails. Think about when one device is only little bit on and the other is fully on.

However, in a bridge amp using 100V devices you can achieve almost 90V swing, which is monster power even into 8 ohms! You would need many parallel devices to cope with this current.
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