I bought a MIM Jazz 4 as a backup bass a few months ago. Very nice for a budget guitar. Anyway, I bought a pair of Kent Armstrong hot vintage jazz pickups off of ebay a couple of days ago and popped them in. Now, each pickup on it's own sounds huge, fat, wonderful and a massive improvement. However, when both are on full you notice a drop in volume and the sound hollows right out, which I assume is a phase cancellation issue of side kind. Is this correct? Is this how a vintage jazz should sound with both pickups maxxed? I'm at something of a disadvantage - for the past 10 years I've been playing active basses, mostly with blend controls rather than dual volume, so I don't have a suitable reference. The stock pickups didn't do it - but then the stock pickups sounded pretty rotten anyway.