low mA led

Hello,
I'm trying to attach an led between the jack and the headphones of a regular set of headphones which would act as a strobe that flashes to the beat. It works, but only on the loudest output we have in our house. I was hoping to make it work for my cd player. I presented the problem to a guy at radio shack, and he said that I probably needed a lower mA led, which would be more sensitive to the low current of a music signal. I bought a couple 15 mA leds, but they weren't any help at all- they still worked, but only when the sound was as loud as possible. I found a couple 2 mA leds online, but I really don't want to order 10 of them and wait a week to get them... I was wondering if I could find an led with a very low mA rating in some toy or something. Does anyone know what would use a very low mA led? I'm not very experienced with electronics and circuitry, so if I'm not making sense, please excuse me lol.

-Thanks

You need a high brightness low Vf led.

A high brigthness Red/Red-orange led would work. Try that out.

Another approach is to use an op-amp or something similar to amplify the signal so that the voltage is high enough to drive the LED at normal levels. The downside is that you need to power the op-amp somehow. The upside is that isolate the non-linear load of the LED from the headphone amp which may make the music sound distorted.

A low Vf LED is a good and easy first thing to try though.

Greg

Radioshack's motto should be "You've got questions, we've got batteries". Their sales people have no clue what they're talking about.

LEDs drop their Vf rating across them. If you take a 9-volt supply and use it to power a 1.7Vf red LED, you'll have 7.3 volts left available for the rest of the circuit. Current is not an issue at all in the problems you're having. If the voltage supplied to the LED is less than the LED's Vf value, the LED will not light.

Audio signals to headphones are in the 10's of milivolts, so you can not power any LED from that source. Even if you could, you'd be taking a linear chunk out of the voltages about Vf and none when it dips below, distorting the sound a lot.

You will need a driver circuit with a high-impedence input and you can't power it off the audio line.

Hey guys, thanks for the advice- this is what I've got so far:
I guess I kinda took the amplifier circuit approach- I hooked up 3 button cells and a variable resistor to the led. If I keep the resistance pretty high, it powers the led just enough to light it dimly. It works, but since I didn't amplify the audio current any, you can just barely notice the difference in brightness, even though the led can potentially be much brighter. I think what I need to do (which is, I think, what greg_in_canada suggested) is amplify the audio current just before the led. Could I build a small amplifier circuit (remember, I'm a noob), and how would I go about that? If not, where could I find a high brightness, low Vf led? I've tried a bunch lying around, and the most successful one, which was still very unsuccessful, came out of a small keychain light powered from the three button cells mentioned above, which had a light blue color (if that matters).


--Also, I should note that none of the led's I've tried have had any (noticeable) effect on the music- it sounds fine still.

Do a web search for "color organ". What you're describing is a one-channel color organ.