So I’m hoping to do something, but I don’t know if it’s realistic. I recently bought a little short scale bass to facilitate practicing by giving me a more portable option for when I'm out and about. Then I got thinking… Every work day I spend about two hours on the bus commuting, and I generally either sleep or argue with people on the internet. But if I had a little portable headphone amp that I could plug it into, I could practice on the bus. And if I could plug a metronome or mp3 player in that’d be even better.
So is there an easily portable solution that’ll drive my headphones (Audio Technica ATH M40-fs), take the ¼” TS from my bass, a stereo input from another device, and let me control them against each other?