Ive got a Thumper somewhere at home. Got it direct from Andy when he was still going and gigged it in my Squier CVP for a few years.
Not sure how to describe it. Nothing special comes to mind, but ill qualify that statement with it was nice. I’d say exactly the same about any P bass pup ive had, inc Fralins.
Echo had a slightly different tone, but all sound like a P bass. I didnt hear as much ‘thump’ as i expected, but it was definitely on the vintage side IIR. Absolutely nothing wring with it at all, but i did replace it a couple of years ago with a DP122, which i now prefer.