I'm 32 years old, I've been playing basses for 18 years and I enjoy testing sound and design more than I do actually playing, 'cause I'm a giant nerd.
I've played a wide range of bass guitars over the years; 4 strings, 5 strings, 6 strings, precision, fretless, jazz, active and passive. Everything has minor flaws, and we all have our own unique tastes both in instruments and how they fit in a mix for the genre's we like.
The sandberg california series is not sold in the UK, they're a pain in the bottox to get hold of from most places! Even Thomann were telling me it would be months before one became available. Demo's online are either poor quality or just very rare to give a customer a real sense of what the instrument is and what it can do.
I was searching for a precision bass, initially heading towards a Fender AM Ultra but I stumbled upon this and decided this mythical instrument was worth chasing - it looked smooth, premium, solid construction and when you talk to people they tend to go "Sandburg are great! I've never played one or seen one but I hear great things!." Its enough for me to relinquish previous desires and search for the myth.
5 string basses tend to be unpleasant at times with the low b lacking clarity and producing too much 'wool.' The sound is sometimes very inconsistent with the other strings. They also tend to be quite a bit heavier than 4 string basses. Active basses drive harder and can distort (though this varies with bass design.)
This is the lightest 5 string bass I have played. The active set up produces a clear and rich, controlled tone and the humbucker significantly helps to reduce noise. The low b string is clear and consistent with the other strings and it feels just what you want a maple neck, precision bass to feel like.
There is an active/passive switch which gives you extra options (this is pull/push) two volume and two tone pots. You can get a jazz bass sound very quickly from this instrument and a powered precision tone even quicker - it really is an all rounder.
With regards to tone, in precision mode - you get a nice natural 700hz 'gung' that gives presence in a mix. In Jazz mode, the humbucker reduces the noise, gives you a nice smooth tone that feels very 150hz'y. You can blend these to really shape your sound with minimum effort. It works great passively but you really do turn the engine on when you power up with a 9v battery.
I hope this helps, I wish I'd had this to read before I purchased but I'm immensely happy I chose to pursue this holy grail.