There has been a mod on the preamp. The original model (which I have), has a 3 band parametric EQ which gives you 6 controls - Bass / Treble / Q / Freq, volume, balance and a preamp bypass switch. Powered by 2 AA batteries it is a bit useless. Well worth a grand though.
Later models have the same preamp which is the one from all the premium ones, which gives you Bass / mid / treble, volume, blend, frequency switch and bypass. Well worth a grand.
Whatever version it is , its well worth a grand.
Difference is - the new one is the 5005OL
and the old one is the 5005E
Ignore the colour variations - they are both the same