I was looking for a 5-octave MIDI (not USB) keyboard to use as a lower organ manual for my Nord Electro 3 73 and also to control my Korg Volca Keys analogue synth. I saw the Ambrose keyboard on Ebay and couldn't believe the low price - nearly half the price of most other 5-octave MIDI keyboards. The brightly-coloured sharp keys (moulded, not painted) were an added bonus. The rear panel has a 5-pin DIN MIDI output, a USB port (which can actually be used to power it via any USB power supply), a 9v power input, two assignable pedal sockets and an on-off switch. The performance controls (all assignable) comprise a centre-sprung pitch-bend wheel, a modulation wheel, octave up and down buttons, an edit mode button, a slider and four continuous encoders, each of which can have two selectable functions. All assignment options are selected via the keyboard, with a handy guide printed above the keys. There are five velocity curves available, but no facility to completely disable MIDI velocity. Additionally, the keyboard has no memory, so you will need to reassign the controllers each time you use it.
For the price, you can't beat it. A fun, colourful and playable addition to any keyboard rig or studio.