I had this thought the other day when I was wondering if I needed a new pracise amp: Some practise amps have headphone jacks. So if you plug in there the speaker isn't doing much. Could you build a little device that plugs into your bass, has the essentials required to process the signal (like a mini amp) and can trasmit it to your headphones? It kind of comes from the same direction as those 2W pocket guitar amps, I was looking for one for bass but I was told there wasn't one and the guitar ones would probably break quickly from being used for a bass. What do you think, is there a chance this would work?