Whilst waiting for the amp to arrive, I had the chance to purchase a used Blackstar Fly 3 Mini Bass, the category leader among cheap, battery-powered bass amps. It is not a close copmarison. The Blackstar, despite being half the cubic volume and only 3W, delivers a wider, deeper range of sounds with less noise, reaching around the same loudness before distorting.
The Joyo is not a nice-sounding amp. The low volume output is usable, but twangy rather than deep. At high volumes it is messy and distorted. The tone control does nothing at all, but this is the least of its problems. What's most striking is that it doesn't even sound good with headphones, so it's not just the speaker to blame. The Joyo also produced a noticeable amount of buzzing noise. This is typical of cheap amps, but also not true of the Blackstar, which by the way sounds gorgeous through headphones.
In the Joyo's favour, it is still light and portable despite being larger. The drive channel is not obnoxious, but the gain must be kept under control for a reasonable sound.
I would recommend spending the extra money for the Blackstar. It will make you very happy. If you can't afford it, pick up a used 10W mains-powered practice amp, or a headphone amp like the Vox Amplug (for private practice), both of which will deliver a more satisfying tone. The only situation in which I would recommend the Joyo is outdoors in public, where battery power is a necessity and sheer loudness may be preferred over sound quality.
I hope in future Joyo can produce an improved version without the tone control, overdrive and fake tweeter, instead focused on producing a deep, clean sound rather than trying to claim '10W' of distortion.
