Sound to light project

[jrz126]

I'm using this circuit here: **broken link removed** and **broken link removed** (The first is just a buffer, the second controls the lights.) I'm also using this circuit: **broken link removed** to generate the -12V
I'm running it in my car and I've had it in there for a couple months now, still on a breadboard. I'm going to solder it to a perf. board and put it in a project box sometime soon.

I was wondering if it is possible to convert the schematic so that I can use a single rail op amp. (LM324 to be exact). I was thinking of just using some resistors as a voltage divider.
The -12V would be connected to the car ground, and the gnd in the schematic would be in the middle of my voltage divider.

 

[Russlk]

You should use a 5 volt regulator to make the mid voltage to avoid motorboating.

 

[audioguru]

You can use any opamp for the buffer if its inputs are biased at half the supply voltage.
Then you can use an LM324 quad or LM358 dual with its non-inverting input connected to ground and the inverting input with the usual input resistor capacitor-coupled from the buffer. It might need a resistor at its output to ground to have very close to zero volts at the output without a signal, then it rectifies the signal to provide a positive output voltage dependant on the instantaneous signal's level. Keep the gain of the inverting opamp low so that its output doesn't clip so the inverting input stays near 0V without going negative which is disallowed.
Use a transistor emitter-follower at the opamp's output which can be used as a peak detector with a slower release time instead of an instantaneous blur of LEDs.