Positive Grid's Spark amp is helpful for practicing musicians, but its size and heft haven't been practical if you've wanted to jam in the bedroom or otherwise venture beyond your studio.

What's more, it's now fully active, with its own built-in 350-W power amp, which allows it to run as a full-range, flat response (FRFR) speaker.

The amp features one channel for microphone or line input and another for guitar, there's EQ to tweak your tone as well as reverb and overdrive, and Bluetooth is cooked in for setting up backing ...

The guitar sports humbucker pickups, a 12-hour battery life and a 20-watt amp to power the speakers. The whole kit weighs under 9 pounds.

New guitar tones can be downloaded into the device, where they run as software rather than as analog electrical circuits in an amp or foot pedal. In other words, the Spark 2 is the latest example ...