XIN SuperMicro-IV

If you want something even smaller, then the SuperMicro-IV is absolutely the smallest top-end amp currently available in this world. Although it does not have the features and its beautiful case is not so rugged, but it does not lose anything on sound. A single AAA battery powers any headphones for 35 hours, thanking to the same 5.5V boost technology used in SuperMini-IV and the latest amplify chips.

2.0"x1.0"x0.7", 1.0 oz (w/batt.), 1 AAA, over-discharge protection, 5.5V boost.