santik wrote:
Mind to show us the how-to on building your power supply?
Not much to say, I suppose. I didn't use Mains transformer, so there's no shock risk. Plus no transformer, so no rectifier bridge. I skipped all that and used a scrapped laptop power supply.
These are typically 15 VDC to around 19.5 VDC, and usually supply plenty of current (2 to 3 amps) AND, they're regulated. But in this case, it was noisy and the voltage was a bit high. So I supplied a few components to filter and lower the voltage to approximately 12.6 volts. Again, my audio experience is the Millet Max, so I stole just the filtering and regulating portion of their power supply.
Basically, from their schematic, I'm using everything from CR1A to the right to CR5.
I found that only 3 of the 4 CR1's were necessary (and more importantly, fit in the enclosure!). Then there's your basic LM317T setup, almost straight from the datasheet, with a trimpot on the ADJ pin so you can load it up and make an accurate final voltage setting. DR3 is there, I believe, to protect the LM317 from any stored voltage upstream; upon power-off, voltage MIGHT flow into the output of the LM317 - not such a big risk since the CR1A,C,D behind it will be holding quite a charge. CR4 and DR2 act to stabilize the ADJ setting. And the final CR5 (tantalum) just to assure output stability and I suppose to send any stray RF to ground. I think a small valued electrolytic might work if no tantalum was available.
And you'll need a small-ish heatsink. Depending on the voltage drop from the input, the LM317 will dissipate P=I*V, or 400ma x (voltage drop) in pure heat output.
This makes an extremely quiet, simple, regulated supply, and you can use any sort of wall-wart, laptop supply, whatever you have on hand for input voltage. However the input voltage will need to be at least 14 VDC or so, to provide headroom for the LM317 to regulate.
Mike Y
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