DVDdoug:
Sure, in the "old days" amplifiers were designed with discrete transistors but it's a LOT easier to use op-amps. With an [u]op-amp circuit[/u] you just need two resistors to set the gain. (But most op-amps only about enough current capability to drive one LED.)
I tried following the non-inverting amplifier circuit exactly, using a potentiometer for R1 and R2 and my audio signal going directly into Input +. I assumed that 0V means ground, and wired it as such. I measured the voltage of Output with my multimeter and the voltage stayed constant regardless of any adjustments to my potentiometer.
Here is my exact circuit:
