Let's see, this is a dirt-cheap mini bass combo, which sounds as it looks: plasticky and thin. It does reproduce bass sounds, albeit with obvious plastic resonance. It distorts quite easily, even on the clean channel, though that can be adjusted with the volume pot on the instrument. The controls are straightforward and work as expected. Bluetooth is easy to connect and stream to as an external speaker. Power supply is standard 9V pedal-like with same barrel connector, meaning it can be powered with a pedal power supply or power bank. A handle or some strap pins would make it easier to grab and transport.
However, one subtle but fatal flaw that made me decide to return it, apart from the sound quality, is that the Bluetooth component connects as a speaker + microphone, when it really only is a speaker. When I connected my phone to stream some songs to play along, it worked fine, until I stopped for a moment to record a voice message, only to see that it had only recorded silence... This is because the phone thinks it is connected to a bluetooth microphone as well as speaker, but the JAMster speaker obviously is only a speaker and has no microphone. The Bluetooth chip should only connect as an external speaker, and this is a minor but annoying flaw. So, back to Treppendorf it goes.