solution to those who say that LED's affect the sound adversely - diyAudio
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Old 8th June 2003, 01:04 AM   #1
elizard is offline elizard  Canada
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Default solution to those who say that LED's affect the sound adversely

Well, after looking over some (quite a few) threads, and reading all sorts of claims of how LED's (i.e. high-brightness blue ones) affect the sound when the power for them is taken from the rails, i decided to find a sensible solution:

well, one was additional transformer/additional winding for a transformer which peter employs .. but i don't feel like breaking the potting of my toroid, and i don't have space for another small transformer ..

so ...
batteries came to mind, 9V specifically

well, i had no 9V batteries lying around, so i picked up a 1.5V (AA? .. or AAA? in any case, A of a sort!) and the LED doesn't work (not enough voltage) ..
two of them work though

no diodes needed, no resistors (in my case, the led is bright but doesn't light up the room .. although it IS still light outside, so i may need to re-evaluate that decision when the sun sets) needed .. and i have a bright red LED on my gainclone supply w/o it effecting the sound at all

btw, for this to work, you can't use a spst switch .. dpst/dpdt is required so that the LED lights up when you press the switch
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Old 8th June 2003, 01:06 AM   #2
elizard is offline elizard  Canada
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oh yeah .. the thread title should be "... adversely affect the sound"
i think .. that sounds right
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Old 8th June 2003, 01:08 AM   #3
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Default A led should have the same effect

as a birthday candle held near your preamp.
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Old 8th June 2003, 01:16 AM   #4
elizard is offline elizard  Canada
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well the birthday candle will eminate some heat, which will warm up your preamp more so at the spot you're holding the candle at, and therefore totally throw off the sound!
especially if you're leaning towards left/right channel and less towards the other
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Old 8th June 2003, 01:19 AM   #5
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hmm, i often lean to the left and right at the same time...

any info on the current draw with 2 AA batteries?
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Old 8th June 2003, 01:39 AM   #6
elizard is offline elizard  Canada
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no clue, sorry ..

the LED's are rated 20mA .. now I've seen one light up at 20mA .. and um, then i fried it shortly thereafter

it seems its about 1/2-2/3 of its brightness .. and its getting to be pretty dark as the sun is starting to set .. although i'll be able to tell when its fully dark in about 2-3 hours ..
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Old 8th June 2003, 01:41 AM   #7
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Quote:
Originally posted by theChris
any info on the current draw with 2 AA batteries?
Well, it will be the total voltage of the two batteries minus the forward voltage drop of the LED divided by the total series resistance of the two batteries.

You could probably get away with a bit of additional resistance (i.e. a resistor) and prolong the battery life.

se
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Old 8th June 2003, 01:43 AM   #8
elizard is offline elizard  Canada
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well the setup i did with the 2AA batteries is just a temporary one to test and see if it works, and if it does, how well

when it runs out i'm going to use a 9V battery, and DEFINITELY a resistor .. probably around 1k should cut it and still be plenty bright ..
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Old 8th June 2003, 02:10 AM   #9
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Quote:
Originally posted by elizard
well the setup i did with the 2AA batteries is just a temporary one to test and see if it works, and if it does, how well

when it runs out i'm going to use a 9V battery, and DEFINITELY a resistor .. probably around 1k should cut it and still be plenty bright ..
Yeah, that'll work. Though you could also just get a little AA battery holder at Radio Shack and stick with the AAs. I was just playing around here with a pair of Duracell AAs and some LEDs with a 3 volt V<sub>F</sub> and even with a 68 ohm resistor I got sufficient brightness.

se
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Old 8th June 2003, 08:17 AM   #10
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As someone with absolutely no interest in LEDs (or birthday candles) i wonder why don't you just put a few turns of wire on top of your toroid and get the led supplied from there.
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