Single LED VU-Meter-like indicator

[felix42]

Hi everybody,

I am looking for a circuit that modulates the brightness of a single LED somehow proportional to the signal level (preferably taken from the preamp output).. It doesn't have to be accurate at all, this is just for eye candy.
I think they use this type of display a lot on bass amps and i think it must be similar to the clipping indicator circuits you see around here.

Can somebody point me in any direction here?

Thanks in advance!

 

[Frank Berry]

felix42,

You might try something like this. It's simple.
Trim the value of the feedback resistor to obtain enough gain to drive the LED.
Use a bi-polar power supply. + and - 15 volts will be good.

Frank

 

[destroyer X]

I think that a limiting resistor, a zener diode and one led

I think this will fit your need.

And the best way is to do it in a experimental way...to see the ligth modulation if fits your needs.

regards,

Carlos

 

[felix42]

Looks good, i'm going to try it out today.

Thanks for your help!

felix

 

[destroyer X]

Hi Felix, this is a thread that may be intersting to you

http://www.diyaudio.com/forums/showthread.php?postid=716046#post716046

aufwiederlehsen

Karl

 

[cpemma]

Here's one that appeared in a Maplin magazine about 20 years ago. I've made single level versions to indicate danger to some 15W outdoor speakers I have. Runs off the speaker power, so audiophreaks beware.

 

[destroyer X]

Cpemma, this circuit works fine...very old really

But it is beeing used inside many good brand speaker around the world, including now a days studio monitors.

regards,

Carlos

 

[cpemma]

Stripboarded unit

 

[cpemma]

There's also a LB1443N "vu-meter" IC, 5 LEDs and simpler/cheaper than LM3915/6 circuits. The NAD3020 schematic linked nearby shows how they combine a signal from both speaker channels.