audio buffer

hi all
I need to build an audio mixer and i am looking for a good opamp for buffers. lm324?
any advices?
thanks

The LM324 is too noisy for quality audio work, and has limited bandwidth, try the TL084 instead. I must be sounding like Audioguru,

thank you .
And I have a 24 v power supple , how to make it bipolar, I mean +12v - 12 and ground.

your 24v supply is either already bipolar, or you need to invert it, in which you'll end up with a 48v supply

if it's a 24vac mains transformer with a center tap then it is 12+12, and if you rectify and regulate it, you could have a nice power supply with +12 and -12 volt rails.

The very old LM324 (as was said) is noisy and has a bandwidth to only 6kHz.
Also, it has crossover distortion caused because it is very low power so its bias current for its output transistors is not enough.

Any opamp can be operated with a single supply if its inputs are connected to a voltage divider at about half the supply voltage. Here is an example: