CIRCUIT DIAGRAM
This runs from a split supply of +12 to +24 volts. It will function at lower voltages but you will have to reduce the input level to prevent distortion from clipping.
An input signal around 500mV should be about the safe limit to give some room for the uneven recording level of many mp3s.
The op-amp used in the simulation was a general purpose 741 type but better quality performance may be gained by choosing a higher quality op-amp specifically for audio applications.
