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Old 31st January 2013, 10:23 PM   #1
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Default Questions about building new power amp

Hello! I'm going to build a new power amp to my new purchased speakers, I've been looking for good schematics on the net but I need a lot of watts, so the only thing I've found is this: Link removed as this project is lethal.
but the only people sheer is that it is "dangerous" to build but I want someone to see if it really works, I have built many smaller amps and have repaired all sorts of electronics whole life so I'm no amateur in the subject.
I also know that it is illegal to build in some countries. and that it is un-insulated against AC-net in some parts, so the only thing I want is a professional judgment if it really works
Or if anyone knows any others simmlar schematics that works

Sorry for bad english

/ / Kim

Last edited by Mooly; 1st February 2013 at 06:32 PM. Reason: Link to lethal unisolated circuit removed.
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Old 31st January 2013, 11:44 PM   #2
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I wouldn't recommend powering an amplifier directly off the mains.
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Old 1st February 2013, 03:40 AM   #3
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I did not much look at the schematic, but 5 kW at 230 V AC line level is about 21.5 A. 75% efficiency, at best brings, that to 28.5 A. Enough power for a stadium that seats 20,000 spectators. I think, I would look for more efficient speakers first to allow me to reduce power requirments! E
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Old 1st February 2013, 03:57 AM   #4
CBS240 is offline CBS240  United States
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You could IF you used the proper rated input transformer, connect the grounding correctly and insure that the speaker is always insulated. If the speakers can't guarantee insulation then you have to use an insulated output transformer. The whole issue is that if parts of the circuit are not isolated from mains then electrocution between the circuit and earth GND can be quite easily acomplished. One solution is a properly rated SMPS. It seems to me that for this much power, you either have a large heater or you would go with a class D type circuit or a switching rail follower power supply.
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Old 1st February 2013, 05:18 AM   #5
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Quote:
Originally Posted by nigelwright7557 View Post
I wouldn't recommend powering an amplifier directly off the mains.
You're being MUCH too nice. That contraption is a death waiting to happen. The irony is that the transformer is an autotransformer which is already pretty big. How much bigger would it be with a properly isolated secondary?

G
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Old 1st February 2013, 05:26 AM   #6
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Quote:
Originally Posted by IPG Event View Post
Hello! I'm going to build a new power amp to my new purchased speakers,
............5000watt amp project schematics

Obviously you are setting your goal much too low. A 50 KW amp ought to be goal
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Old 1st February 2013, 05:48 PM   #7
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Okay thanks for the quick response!

Is there anyone else who has reached similar schematics that works then or they are difficult to get hold of? they are expensive and difficult to build is not important only that they work well, I've found schematics that put out around 1.500 watts / CH that seems to work, and would do if I did not get something else

or is there anyone who knows any other site there i can look?

/ / Kim
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Old 1st February 2013, 06:35 PM   #8
Mooly is online now Mooly  United Kingdom
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Quote:
Originally Posted by stratus46 View Post
You're being MUCH too nice. That contraption is a death waiting to happen. The irony is that the transformer is an autotransformer which is already pretty big. How much bigger would it be with a properly isolated secondary?

G
Indeed !

Which is why I've taken the very unusual step of editing a post. The link in the first post has been removed.

As long as the discussion keeps to normal amplifiers (safe isolated transformer powered) then the thread will stay open.

What do need 5000 watts for anyway
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Old 4th February 2013, 01:54 AM   #9
dangus is offline dangus  Canada
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Unless you have access to extremely cheap surplus parts, it's generally cheaper to buy a used power amp. They can be worth buying just for the parts alone, since big heatsinks, transformers, filter caps, and cases cost a lot if you're buying them in small quantities.

The Behringer digital amp is worth a look. Also those digital amp modules from places like Digital amplifier modules from CAD AUDIO DK
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Old 4th February 2013, 02:00 AM   #10
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Originally Posted by dangus View Post
They can be worth buying just for the parts alone, since big heatsinks, transformers, filter caps, and cases cost a lot if you're buying them in small quantities.
The case is worth a bit too. Having to hack out mains sockets etc on a new chassis is a real pain.

I sometimes use PC cases for amplifiers. It has a mains input socket and holes for fans.

Take care when buying second hand smoothing capacitors as it is likely they are approaching the end of their life.
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