Go Back   Home > Forums > Live Sound > PA Systems

PA Systems A forum for discussion of all parts of a sound reinforcement or DJ system: loudspeakers, mixers (desks) etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 27th January 2011, 07:21 PM   #1
effebi is offline effebi  Italy
diyAudio Member
 
effebi's Avatar
 
Join Date: Nov 2010
Location: Milan
Default 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

Last edited by effebi; 27th January 2011 at 07:23 PM. Reason: spelling
  Reply With Quote
Old 27th January 2011, 07:44 PM   #2
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
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.
__________________
http://www.murtonpikesystems.co.uk PCBCAD50 pcb design software.
  Reply With Quote
Old 27th January 2011, 09:23 PM   #3
diyAudio Member
 
Federmann's Avatar
 
Join Date: Oct 2009
Location: Kunovice - Moravia
Send a message via ICQ to Federmann Send a message via Skype™ to Federmann
Here http://www.diyaudio.com/forums/solid...-9240-a-2.html
  Reply With Quote
Old 27th January 2011, 09:36 PM   #4
effebi is offline effebi  Italy
diyAudio Member
 
effebi's Avatar
 
Join Date: Nov 2010
Location: Milan
Quote:
Originally Posted by Federmann View Post
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
  Reply With Quote
Old 27th January 2011, 09:40 PM   #5
diyAudio Member
 
Federmann's Avatar
 
Join Date: Oct 2009
Location: Kunovice - Moravia
Send a message via ICQ to Federmann Send a message via Skype™ to Federmann
Two modules for bridge

±50V

4Ω

Last edited by Federmann; 27th January 2011 at 09:42 PM.
  Reply With Quote
Old 27th January 2011, 09:45 PM   #6
diyAudio Member
 
Federmann's Avatar
 
Join Date: Oct 2009
Location: Kunovice - Moravia
Send a message via ICQ to Federmann Send a message via Skype™ to Federmann
Power supply±35V 1000W/2Ω
Power supply±50V 1000W/4Ω
Power supply±70V 1000W/8Ω
  Reply With Quote
Old 27th January 2011, 09:48 PM   #7
diyAudio Member
 
Federmann's Avatar
 
Join Date: Oct 2009
Location: Kunovice - Moravia
Send a message via ICQ to Federmann Send a message via Skype™ to Federmann
Or, one module with 10 pairs IRFP240/9240
  Reply With Quote
Old 27th January 2011, 09:58 PM   #8
effebi is offline effebi  Italy
diyAudio Member
 
effebi's Avatar
 
Join Date: Nov 2010
Location: Milan
Quote:
Originally Posted by Federmann View Post
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
  Reply With Quote
Old 27th January 2011, 10:01 PM   #9
effebi is offline effebi  Italy
diyAudio Member
 
effebi's Avatar
 
Join Date: Nov 2010
Location: Milan
Quote:
Originally Posted by Federmann View Post
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

Last edited by effebi; 27th January 2011 at 10:01 PM. Reason: spelling
  Reply With Quote
Old 27th January 2011, 10:09 PM   #10
diyAudio Member
 
Federmann's Avatar
 
Join Date: Oct 2009
Location: Kunovice - Moravia
Send a message via ICQ to Federmann Send a message via Skype™ to Federmann
Quote:
Originally Posted by effebi View Post
Is the driver circuit capable to handle the extra 5 pairs?
Yes, it is capable of.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Preamp with limiter schematic, need some hints petrol vendor Instruments and Amps 0 15th August 2008 05:48 PM
Class-d for a 1kw PA amp MikeHunt79 Class D 4 30th December 2007 06:19 PM
Hints for starting a KG amp. Garbz Solid State 3 14th March 2004 10:31 AM
Scott Joplin: need hints! dice45 Music 12 19th August 2002 01:36 PM


New To Site? Need Help?

All times are GMT. The time now is 01:57 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2