Viridian has the best idea. If you can solder you can build a passive with Radio Shack parts for about $10 that will amaze you with how good it sounds.
Project Enclosure 3x2x1" $2.29
Catalog #: 270-1801
Phono (RCA) Jack, 4 pack $3.99
Catalog #: 274-346
100K Ohm Stereo Control $3.29
Catalog #: 271-1732
A little wire and solder and a knob if you wish and you are in business. I can email you instructions if you wish.
Project Enclosure 3x2x1" $2.29
Catalog #: 270-1801
Phono (RCA) Jack, 4 pack $3.99
Catalog #: 274-346
100K Ohm Stereo Control $3.29
Catalog #: 271-1732
A little wire and solder and a knob if you wish and you are in business. I can email you instructions if you wish.