audio activated LED

Thread Starter


Joined Feb 21, 2010
I'm a musician with a home studio.

The use of a click track/metronome is a common practice, however in order to keep the click loud enough in the headphones it is a distraction for many as it 'competes' with what they're playing... or in the case of drummers, because drums are rather loud all by themselves, if the drummer gets into the beat then his own playing becomes louder than than the click

so, I'd like to take an output level from my system on a separate output (which would normally be routed to a power amp or used by the input of another audio device) and trigger an LED. The circuit must be capable of upwards of 180 beats/blinks/flashes a minute (though 90 - 13 is more typical)

I believe the the visual "click will be much easier to play to than having to divide one's listening concentration between the click, the mix and one's own playing.

These click itself can be varied from something akin to the sound from the old PONG games to more like a cowbell or woodblock tap... as well as the tick, tick, tick of a metronome. Frequency is not too important, more the threshold level for the impulse/ wave spike

I looked at the old color organ schematics, but most have the frequency networks and a ss relay was used to power 120 v lighting (I think most of the early color organs used "christmas" lights.

an intensity control might be useful, but simple would be fine and powered by a wall wart even better


Joined Aug 7, 2008
Is the "click" much louder than background sound, at clicks position? Microphone, audio voltage amp.,comparator, 555 IC, LED.

Thread Starter


Joined Feb 21, 2010
I can control the level of the click, so I Believe I could adjust the level to reach the LED 'threshold'

because the click signal can be isolated, there are no other signals for it to compete with

to be clear- I do not want to use a microphone to pick up the click- it will be a direct output signal from the interface


Joined Nov 13, 2008
Feed it to a 555 timer. Set the timer for the length of the "on" time you want for the LED.
I'm guessing you can drive the LED directly from the 555 but you might want to use a transistor buffer.
You might need to condition the audio before the 555 trigger.
A simple transistor detector circuit ahead of the timer.