The circuit is a LPF with a buffer stage in front of it that uses a linear pot. to control gain & attenuation. The setup is such that the response of the linear pot. is similar to a log. pot..
A single 5V power supply is a known limitation, however the design must have this.
The 1st stage gets input from a CD player (low Z output), this goes to the buffer with DC offset added. This goes to a 2nd stage which sets the potential gain that can be set by the pot. by the ratio of R6/R5. Next, the LPF.
The circuit uses 3 op-amps and 2 levels of DC offset are added. If the circuit could be simplified it would be great. Thanks!