h a l f b a k e r y
Contrary to popular belief
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I'm gonna need one of these next weekend, and will probably build a prototype.
Most large pro-audio mixing consoles feature a BNC connector to provide power to a gooseneck lamp so that the operator can see the console in dark of near-dark conditions.
But smaller mixers don't include this feature,
and larger boards could benefit from additional lighting.
Most professional and many semipro mixers feature "phantom power" to provide small amounts of power at ~48 Volts intended to provide power to professional condensor microphones.
This idea is a gooseneck lamp with an LED lamp which plugs into and derives its power from an unused mic input connector using a small part of the 48V at a few mA available there.
Pro Audio meaning [csea, Oct 24 2011]
Bayonet Neill Concelman [csea, Sep 17 2013]
||Low power is right - you probably shouldn't draw more than about 2 mA, which gives you about a tenth of a watt. That should be enough to dimly illuminate a mixing board, though.
||To get the best efficiency and the least possibility of noise I'd simply wire the LEDs (about 16) in series. If the voltage drop of the LED chain at their minimum activation voltage is close to 48V, their (slightly positive) voltage-current curve, along with the power supply's internal resistance, should regulate the current nicely. Err on the side of low current, though. Just my 2 cents worth.