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Putting the components together nice and close, using a project board I had left over from other things. It's cut to size to fit into the small project box slots to be held in place. The missing corner is to run wires from the front to the back without having the project board interfere. The big golden component on the right is a 10uH RFI suppression coil. |
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Solder side of the same board - still missing a few parts, but you can see that there's not a whole lot of stuff to solder. Later I added a resistor and some leads to a status indicator LED and the input/output wires. |
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Looking into the finished box - front (left) is the DPDT switch to select on/charge mode. Red wires on that side go to a small green status LED to show me if I am on or off (=charging). The big silver thing is a heat sink I ripped off an old computer motherboard voltage regulator and screwed to the L7805 regulator: there's quite some heat coming from the regulator, however, this heat sink is much larger than what is actually needed. I figured bigger is better and free is even better, so that's why there is such a big piece of aluminum in there. the blue part is a 500 ohm resistor to keep the LED happy at 5 volts. Right side shows the red heat shrink I put on a big 2 amp ceramic fuse which I just soldered inline. There are also the three inputs/output connectors. Those connectors are the most expensive part of the whole project... |
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Angled view to show LED and the idiot labels I put on all connectors to make sure I don't put the charger on the wrong jack, etc. |
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Here's the entire setup, replacing a wallwart. The wires are kept long so that I can run the switch box upstairs, while everything else is in the basement. |
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This picture shows a close-up of the connector and the heat-shrinked connector inserts of the wire that connects to the jack of the original USB receiver power input (I cut that wire and inserted a female molex connector to match this one - the original AC power supply also has a matching plug, so I can alternate battery or AC). The wire ends are heat-shrinked here, since I had to poke this end of the wire through a small hole in my ceiling and didn't want it to get hung up in insulation, etc. It also shows a small 10.000pF XR7 capacitor between the leads which sits more or less right on the plug next to the USB receiver. This is supposed to be the best placement for the small bypass caps on a digital power supply - close to the consumer. |
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View of the switchbox with the lid closed. This is a very small box that fits on top of my main DAC battery and does everything I need it to do with one flip of the switch: power down the USB hub and go auto-charge the battery. Having the switch next to the DAC allows me to power down the hub before the DAC and then power up the DAC before the USB hub when I want to listen again. This trick prevents Windows XP from complaining about an "unrecognized USB device" - dropping the hub and powering it up again goes very smoothly and no reboots are required. Without this little toggle switch I'd have to reboot the PC after each DAC battery recharge, so there's a good reason for going through all this effort and having the power switch upstairs where the DAC is located. |
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