Tape off any areas on the cabinet that you do not wish to refinish. If there are large areas that you do not want affected by stain or sealer, cover them with plastic and secure the plastic with painter's tape.
Sand away the old finish with medium-grade sandpaper, followed by fine-grade sandpaper. The first sanding process will strip the finish; the second will make the wood smooth. Wipe the bass cabinet down with a damp rag.
Apply a small amount of wood stain to the cabinet with a paintbrush or clean cloth. Spread the stain with the wood grain. Allow the stain to soak for about one minute, then wipe up the excess with a fresh cloth. Allow the stain to dry.
Coat the bass cabinet with a thin layer of wood sealer, such as varnish or polyurethane. Use a soft-bristled paintbrush or a foam or lamb's wool applicator. Allow the wood sealer to dry. Lightly sand the wood sealer with very fine-grade sandpaper, then wipe the dust away with a moist cloth. Apply a second coat of wood sealer.