I'm a new Big Singles owner as of this weekend. Dropped a pair into my Dingwall Z1 with an Audere 3ZB 4-band preamp.
Had first rehearsal w/ band yesterday, gotta say my first impressions are wonderful, with only one hesitation - some buzz. I did shield the pickups w/ copper foil, but didn't wrap them as completely as Mike at Nordstrand had suggested, so I will redo in a week to see. Forget running them naked - gotta shield these beasts. I noticed no appreciable loss in hi freq w/ shields either.
Otherwise, the sound was breathtaking. This is now the most powerful sounding bass I have owned, but I must qualify again - this was with the Audere preamp set to "low Z" mode which other preamps won't do, so YMMV. With the mid or hi Z positions, more like a standard pre, it is your typical bright modern sound, but I didn't spend any time at those settings because of the buzz.
But coupled with the low Z setting they have a wonderful ability to convey the dynamic of the string pluck. The low-mid attack is devastating, super punchy, and super fast. I was able to play extremely short stacatto notes, shorter than ever before, and the full attack was there. Very satisfying in a live situation for rock or popular music. The lo-Z sound is thick with bass and low-mids, but not like turning tone controls - you can still hear upper-mids and the full character of the string. Really a sound you have to try. Listening to a sound sample won't do it - there is a fast and resonant, bell-like quality to the attack that you have to play to appreciate. I'll report more as experience grows...