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Old 19th August 2008, 04:59 AM   #1
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Default LED source indicator

Hi i'm about to build my first gainclone and i am wondering how i would go about connecting LED's to indicate which source i have selected. It will be three inputs, the switch is a four pole three way.
Thanks in advance
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Old 19th August 2008, 06:53 AM   #2
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Connect the LED to one of the four poles that is not used for the audio signal through a resistor. The resistor is calculated to be (U-Uf)/If, where U is the available voltage, Uf is the LEDs forward voltage and If is the LEDs forward current.

E. g. if you have 24 V and use a LED with Uf=2V and If=20mA, your resistor should be bigger than (24V-2V)/0,02A=1100Ohm.
Increasing the current can reduce the LEDs lifetime seriously.
Take care about the resistor wattage. In this example the resistor dissipates 22Vx0,02A=0,44W. A single 1/4W resistor will not do for that task.

The other pin of the switch goes to one side of your supply voltage. The second pin of the LED goes to ground. Watch the polarity. The longer pin of the LED goes to (+) the shorter one to (-). So, if you connect V+ to the switch, the longer LED pin goes to the other pin on the switch. If you connect V- to the switch, the shorter LED pin goes to the other pin on the switch.
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Old 19th August 2008, 07:28 AM   #3
Mooly is online now Mooly  United Kingdom
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20 milliamps That will look like Blackpool Illuminations . A modern LED will probably be bright enough on a tenth of that, all good advice though.
What colour will you use ? Blue sounds best you know , or was it green
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Old 19th August 2008, 07:38 AM   #4
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yeah blue will definately 'sound better'

I'm still a little confused as to that explanation. Could anybody clarify that any further. And pretend you're trying to tell a 6 year old because i don't have a great deal of electrical knowledge.

Thanks heaps
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Old 19th August 2008, 07:53 AM   #5
Mooly is online now Mooly  United Kingdom
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Take a wire with the resistor in series with it and connect to the PSU positive. Connect this lead to the wiper of the switch. Connect the 3 LEDS, one to each contact on the switch and return all the cathodes (short legs ) to ground. If you are still not sure I can draw it but try and figure it out. Use a 9 v battery with the resistor to do so. Just remember to always have a resistor in circuit with the LED.
And your going to build an amp
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Old 19th August 2008, 10:24 AM   #6
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Quote:
Originally posted by snails07
yeah blue will definately 'sound better'
Blue sounded better not long ago. Nowadays the best sound comes from orange, violet or pink. BTW you get the cosiest sound from warm-white.
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