Best LM3915 circuit for line level monitoring

[danrogers]

Best LM3915 circuit for line level audio monitoring

Hi, Ive been looking for LM3915 circuits and LOTS have shown up.

I would like one in which the led's intensity can be varied, and it will be for a stereo application so I guess I will be mirroring the circuit. Also a trimmer to adjust the sensitivity would be nice if possible?

I want to use the standard 10 leds per L & R.

any advice on the best and most efficient circuit would be great!

 

[danrogers]

has this one been tryed and tested? seems to be the most simple that should do the job hopefully.

something I have also wondered about is the possibility of using a few IC's with some filtering circuits before the audio reaches the IC's for spectrum anaylsis?

cheers

 

[ericgibbs]

hi Dan,
Look here:
https://www.electro-tech-online.com/threads/lm3915-vu-meter-help.105292/?highlight=lm3915

Also Search the Forum for LM3915, lots of info.

 

[danrogers]

Hi there Eric, I did actually read through that thread earlier. I guess the suggestion from audioguru using the op amp is just designed to pick up the peaks more accurately?

And I would build that particular circuit along with the one I have posted?

 

[ericgibbs]

hi Dan,
The option you posted is too basic, all you would see on the LED's is a blur.
agu's option has a preamp and rectifier/smoothing stage that will register and hold the peaks long enough to be see clearly.

 

[danrogers]

Thanks Eric, i will give it a blast with the guru's stage pror to it

edit.. I know he uses an electret mic with his meter but I will be using a line level input, will the preamp still be needed?

 

[ericgibbs]

Thanks Eric, i will give it a blast with the guru's stage pror to it

edit.. I know he uses an electret mic with his meter but I will be using a line level input, will the preamp still be needed?

hi
As the audio LINE input is 'ac' you will require rectification of the signal into 'dc', also some smoothing after the rectifier.
'agu's peak detector/rectifier circuit will do that.

 

[sammy004]

Hi Dan I'm accually working on a simular product just need some help on the PCB but you can check out my post at you can see the design that might work for you.
https://www.electro-tech-online.com/threads/my-first-project.108177/