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rwaudio 18th February 2007 04:36 PM

beginning of a car amp
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I've built many car audio processors, and modified a number of amps, but the smps has kept me away from building one from scratch... well I thought I'd give it a try with stuff I had on the bench, and amazingly it's very simple and straight forward.
this is a 13v to +- 31.5v smps and should be good for about 200-300w (evantually) for the moment there is only one IRF540 per phase (to minimize loss of magic smoke during testing etc)
As for sound,( powering basic test pair of LM3886) there isn't a big difference between it and the linear ps I've been using, the highs seem a little brighter, but perhaps lacking a bit of detail aswell, there has been no attempt at better filtering, and this setup has much less filtering than my finished LM3886 gainclone, so the comparison may not be fair.

I plan on building a 4 channel LM3886 "carclone" for the fronts/rears and have get to decide on what to power a pair of JL Audio 10W0's with..

rwaudio 18th February 2007 04:37 PM

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another pic..

1moreamp 18th February 2007 05:53 PM

Try adding bypass caps or a RC type snubber across the rectifiers to lower the noise from that source, and possibly add inductors to the rails to polish you DC a bit. And a RC type snubber circuit across the secondary of your toroid.

This should help reduce some of that brightness issue you having.
Extra caps only help so much. as these power supplies have a fair amount of HF noise to be dealt with. Almost all of the big name builders use what I have suggested in commercially available amps.

Hope this helps:)

Nice beginnings by the way :)

luka 18th February 2007 06:51 PM


Nice project. If you want to get some more info. you can read this thread.

I have something just like that/with LM to power my sub in car. It is not strong enough but it can deliver great basses.

rwaudio 26th March 2007 12:39 AM

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well my newest "carclone" is almost ready for final testing, all the assembly is done, just need to bolt it all together and put on the thermal grease.
some pics...

rwaudio 26th March 2007 12:46 AM

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I should probably mention, it's a 4 channel amp, using 4x LM3886 in a non-inverting setup. SMPS is based on the SG3525 unregulated putting out +/- 33V (no load, I expect that to drop)
this will be powering a set of JL Audio VR 6 1/2" components and the factory 6x9's in the rear.

Whortless 26th March 2007 12:53 PM


I think, someones thinks same things like me. Congratulations, this is a nice idea. But , if I were you i would use the original power supply board of the broken amp.
Please have a look this link :


rwaudio 27th March 2007 12:23 AM

I actually did that initially.. I used the power supply from the broken amp (actually it was the power supply that was broken, so I fixed it and used it, and tossed the audio section out.)
here's the thread for that..

but I wanted to make my own amp from scratch, so this time only the heat sink and the first 1/2" or so of the board (with the terminals attached) was used, it's a little more satisfying this way, and for my future amp projects I had to get the hang of making my own smps.

Whortless 27th March 2007 10:10 AM

Ok, I see. Is your amplifier better than the removed solid state in sound quality? I wondered the sound.Because, i am desinging similar amplifier.

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