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-   -   Some hints for a 1kW PA (http://www.diyaudio.com/forums/pa-systems/181987-some-hints-1kw-pa.html)

effebi 27th January 2011 07:21 PM

Some hints for a 1kW PA
 
I would like some hints for a design that I have to start in the near future.
I am not asking that somebody else is designing for me, just to get some open minded ideas from competent people.
So the design constraints are : load is 2 Ohm at best, maybe al little worse.
Power supply is already there, 65-0-65 V. This should account for ab 1 kW r.m.s. on 2 Ohm. THD I am tolerant, 0.1% would suffice. Band pass is important from the extreme low (ideally DC) to 10kHz .
But I would like to concentrate on the output stage, at the moment.
So would MOSFETs bring any advantage? I know by sure that with 10 pairs BJT (TO3s) it can be done , but also I know that thermal runaways are a problem.
Would it be good to go for class H with a such low rails?
The input and VAS I would prefer IC, also do you have hints for a really rugged one, that can take care of some kind of SOA protection as well?.
Any constructive suggestion will be very appreciate.
Thanks in advance to all
effebi

nigelwright7557 27th January 2011 07:44 PM

The view on BJT or MOSFET is split from what I have seen on here.
Personally I get on well with MOSFETs. So long as you use a Vbe multiplier they are usually fine. If your arent sure go for lateral MOSFETs as they arent so fussy about thermal runaway.

I dont usually bother with protection for a home amp but I do have a DC offset trap using a PIC micro on my disco amp. I suppose it depends what the chances are of shorting the output during normal use.

Federmann 27th January 2011 09:23 PM

Here http://www.diyaudio.com/forums/solid...-9240-a-2.html

effebi 27th January 2011 09:36 PM

Quote:

Originally Posted by Federmann (Post 2448528)

Superb ampli, I had seen already the thread , thank you.

But I really doubt that it can do 1000 W on 2R with only 5 pairs:(, PA service.
BTW do MOS show any real advantage on very low output impedences?
effebi

Federmann 27th January 2011 09:40 PM

Two modules for bridge

±50V

4Ω

Federmann 27th January 2011 09:45 PM

Power supply±35V 1000W/2Ω
Power supply±50V 1000W/4Ω
Power supply±70V 1000W/8Ω

Federmann 27th January 2011 09:48 PM

Or, one module with 10 pairs IRFP240/9240

effebi 27th January 2011 09:58 PM

Quote:

Originally Posted by Federmann (Post 2448552)
Power supply±35V 1000W/2Ω
Power supply±50V 1000W/4Ω
Power supply±70V 1000W/8Ω

I have problems to understood your extra - short comments, sorry.
If you mean as a simple amp, you are calculating more than double the power you can obtain with such rails. If you mean bridged, you must consider that the load seen by a bridged ampli is half than the actual load. I do not belive that is good to go so low as under 1 Ohm, unless you have tried so already with your beautiful amp.
Anyway I am bound to stick with 65-0-65 rails.
thanks
effebi

effebi 27th January 2011 10:01 PM

Quote:

Originally Posted by Federmann (Post 2448555)
Or, one module with 10 pairs IRFP240/9240

This makes perfectly sense.
Did you show the schematic , BTW?
Is the driver circuit capable to handle the extra 5 pairs?
effebi

Federmann 27th January 2011 10:09 PM

Quote:

Originally Posted by effebi (Post 2448567)
Is the driver circuit capable to handle the extra 5 pairs?

Yes, it is capable of.


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