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Old 3rd November 2004, 09:49 AM   #1
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Default VERY HIGH POWER Class D to run from 12V

As per the title, im looking at building a powerfull class d amp, tbh i really dont have a clue where to start, i have built amp circuits in the past from kits etc but as far as design goes im clueless

Basically im looking at making a amp which can produce 5000 watts or so at 1 ohm. So the outpud needs to be somewhere in the region of 75V and capable of switching 75Amps
The usable frequency bust be between 10Hz and 80Hz

The amp does not need to be good quality just efficient and very powerfull, Does anyone have or can anyone draw up a schematic for a basic circuit that will do the job? It does not need any bells and whistles like protection etc, im just after pure power.

Many thanks in anticipation
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Old 3rd November 2004, 12:31 PM   #2
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Designing (or even building from a schematic) something with that kind of power at that kind of impedance is not for the faint hearted. Throw in the added problem of a switching PSU to cope and you may as well forget it.

I'm guessing a little from your sig here as to what your intentions are. If you are adding another (pair of?) speaker to achieve your desired SPL, just add another amp for it. Paralleling speakers on one amp is just a foolish way to do things, IMO. You give yourself massive current transport problems and actually lower your achieveable output because of huge losses.

If you really must use one amp, and you want to build your own, you would be far better off making an amp that puts out high *voltage* rather than current, and connecting drivers in *series* to gain *higher impedance*. This results in much less current demands, making everything easier and less lossy.
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Old 3rd November 2004, 07:52 PM   #3
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ok, so how about a 4 ohm load then? i know its a big ask if its not possible i guess i will have to do it the old fashioned way i was looking for a challenge to pass my time over the winter. I wouldnt be able to use the amp for competitions as it would not be commercially available, i just wanted a little play But yes it would be nice to push the 150dB barrier
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Old 3rd November 2004, 10:35 PM   #4
IVX is offline IVX  Russian Federation
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hi,
Probably 5k@1ohm class D sub amp with enough sound quality for SPL is quite simple task vs SMPS for it. About 500A@12V!! As far as i know, for 150db sufficiently two 12" subwoofers and 1 up to 2Kw.
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Old 4th November 2004, 02:38 AM   #5
ghemink is offline ghemink  Netherlands
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Quote:
Originally posted by danielkelley10
ok, so how about a 4 ohm load then? i know its a big ask if its not possible i guess i will have to do it the old fashioned way i was looking for a challenge to pass my time over the winter. I wouldnt be able to use the amp for competitions as it would not be commercially available, i just wanted a little play But yes it would be nice to push the 150dB barrier

I guess with 150dB you blow out the windows and roof, but probably those are already heavily reinforced.

Have fun, this stuff is not my cup of tea. If I would have to do it, I would like the other replyer use more amps.

Gertjan
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Old 4th November 2004, 05:36 PM   #6
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my current amp pulls around 350 amps at full power, producing around 3000 watts. it will only be run for very short perids of time, i can sustain 12V with 1200amp draw for upto about 10 seconds. It will only need to operate for about 3 secconds so this shouldnt cause a problem.
Do you think it would be easyer to modify my current amp to do the 5000 watts or start from scratch? As said SQ is not a issue it will only be used to play a 54Hz sinewave (or there abouts) not for listening to music.
Is there somewhere i could get a schematic? I know i can get schematics for other 3000 watt amps but they have loads of computerdriven protection/logging systems built into them which i do not need. If i got a copy of them would anyone here be able to loose all the non applicable junk and modify to do 5KW?
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Old 4th November 2004, 05:36 PM   #7
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ohh the reason i would like 5kw from one amp is i would like to use 2 of them to put 10KW through my sub. (yes i know i am a looney, but i also knowthe sub will take it for 3 seccond burps)
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Old 4th November 2004, 06:07 PM   #8
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I think you are on the wrong track. Your sub voicecoil may be able to take the 3 second burp, but often overlooked is the excursion capability of the speaker. To go up 3dB you need to double excursion. I'm confident you will break your speaker(s) if you try it, as you must already be pushing some massive excursion.

As for modding an amp, it's possible. But the gains would probably be negligible. You would need to rewind the power supply transformer to give out higher voltage. The problem with this is the core is probably already not far off saturation (if not already), so the supply would just collapse to the same level as before anyway.

I'm assuming you are already running at 1 ohm. If you are not, you could try this for 3 sec burps, at no cost except an amp that will not last very long and may well break after a few goes. As said above though, I'm confident this is not worth trying due to the speaker excursion being the limiting factor. Even if you could somehow measure excursion and keep to a limit, it would probably only get you 0.5 dB tops.
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Old 4th November 2004, 06:22 PM   #9
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Excursion at the tuning frequency is pritty low as the box it stned to 51Hz to peak at 54Hz, due to playing at the tuning frequency the excursion is minimal. i know the sub can handle 10Kw people have run 12 KW into one of these.

Im currently running a 0.75ohm load, but due to impedance rise due to the box the amp is actually seeing a 2ohm load so it is running the full 3000 watts possible.

Could i not use bigger cores then rewind accordingly? I know these amps can be run off a 18 volt supply for competitions (making them produce in excess of 4000 watts) so would i be able to rewind the power supply torroid to give the amp the impression it is receiving a 18 volt feed?
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Old 4th November 2004, 10:06 PM   #10
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How many speakers are you running?

It depends on how the amp PSU works whether you will actually get any increased output with rewound secondary or primary, or more input voltage. If the design is such that the amp rails are regulated (fixed) then you are wasting your time. If there is no regulation/feedback taking place then you have room to experiment. I would have thought that a high end amp would use regulation. But maybe SPL competition amps don't have this. Yuk.

However, without specialist equipment, knowledge and experience you are limited really to just upping the secondary voltage. If you start messing with the primary the chances are you will run the core into saturation and fry the switching devices. It's too fine a balance between working and fire at those kind of power levels.
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