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Class D Switching Power Amplifiers and Power D/A conversion

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Old 3rd February 2013, 01:38 PM   #1
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Default Newby help if you'd be so kind.

Hi all, I'm new here and new to DIY audio but like with everything else in my life I've jumped in at the deep end, having done so I need some guidance, I am an amature dj and full time mechanical engineer. My problem is this, I recently bought a 15" subwoofer and enclosure believing it to be an active one, goes to show you should read the eBay ad very carefully, I bought it because it matches my full range setup which is active and I was happy with the clarity and output they provide so I've decided to keep the 15, so now my problem, I need some one to basically hold my hand and walk me through this bit.

I'm looking for a circuit that I can build to make the sub an active unit, so I need power supply, amp and preamp diagrams, this won't be my first pcb build but I've never designed one and wouldnt know how to so any help would be greatly appreciated, the subs requirements are 600w rms 1200w peak and at 4 ohms, in the back of the plastic enclosure is a recess covered by a steel plate, the recess measures 200mm wide, 400mm tall and 85mm deep, so what I'd like to do is utilise this space for the amp, power supply and preamp. As its an injection moulded enclosure I assume that the manufacturer would have done this rather than have two moulds. Anyway any help would be much appreciated, and in return I will do this as a how to for other newbies, then everyone can learn from my mistakes along the way.
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Old 3rd February 2013, 04:29 PM   #2
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As a newbie you might be better buying an amplifier module rather than starting from scratch.
There are loads of vendors online who will provide a good quality amplifier pcb with heatsink.
You will pick up a pre amp circuit by doing a search too.
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Old 3rd February 2013, 04:34 PM   #3
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600 Wrms is serious power... first question I would be asking is whether or not you really really need that much.
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Old 3rd February 2013, 04:34 PM   #4
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Thanks but as I said its not my first pcb build infact the last one was an ecu for a v6 engined mk6 escort the one before that was an ac/dc tig welder, I'd rather build one from scratch and I have a 3 axis cnc that I built to make the pcb's with. That's how I find I learn best is by rolling up my sleeves and getting stuck in.
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Old 3rd February 2013, 04:37 PM   #5
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Quote:
Originally Posted by Mooly View Post
600 Wrms is serious power... first question I would be asking is whether or not you really really need that much.
I'd rather have it and not need it than need it and not have it if you see what I mean, I can always turn it down if its too powerful but if its too weak I can't turn it up.
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Old 3rd February 2013, 04:44 PM   #6
Mooly is offline Mooly  United Kingdom
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Very true, as long as you are sure Have a read at this for interest though,
A Test. How much Voltage (power) do your speakers need?

I'll admit Class D isn't really my thing and I don't know what is available for those sort of powers. For conventional amps you won't fit a 600 Wrms amp and PSU in that space. The heatsinking needed will be huge.
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Old 3rd February 2013, 04:48 PM   #7
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Yeah I expected the heat sink to be external to the rest of the components, if for nothing more than having a better air flow to aid cooling, so the space on the inside would only be for the pcb's and their attachments.
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Old 3rd February 2013, 04:54 PM   #8
Mooly is offline Mooly  United Kingdom
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I don't really know what to suggest tbh. Class D is the most efficient and coolest running but 600 watts. Is there such an amp ?

Other conventional amps. Well 600 Watts RMS into 4 ohms means an output of 50 volts RMS. You could look at bridged amplifiers where the speaker is connected between two identical amps and where one is fed with a 180 degree out of phase signal.

Bridged and paralleled amplifiers - Wikipedia, the free encyclopedia

Its a tall order.
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Old 3rd February 2013, 05:23 PM   #9
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I expect there are amps out there that are more powerful than my needs, I used to install car audio and vibe produce a 1200w mono block that was stable at 2ohms and that was a middle of the road amp, I've installed 4000w 1ohm mono blocks but that was car audio and I've no idea what went on inside them but I know they exist.
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Old 3rd February 2013, 06:23 PM   #10
Mooly is offline Mooly  United Kingdom
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I don't know what to advise you really.

Car audio always seems to be marketed differently but I've never studied it in detail so can't comment.
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