Bart XTBT in a Zon?

[VifferMike]

So I'm finally digging around in my Zon Sonus 4's control cavity after owning the bass for a few months. It's a mid-90s model (ser. #93289) with the two J-style Bart pickups and the two stacked knobs for volume/volume and bass/treble ...

Now, I was under the impression that Sonuses has Polyfusion preamps almost exclusively until the late 1990s, especially the ones with the dual, stacked control knobs. In fact, I'd thought the dual stacked-knob layout was a reliable giveaway that a Sonus had a Polyfusion in it. So imagine my surprise when I see that the preamp in mine isn't a printed-circuit-board Poly, but a Bartolini preamp that I've never heard of before: A Bart XTBT.

Anyone know anything about this preamp, and whether or not it was ever stock on Zons?

[The Penguin]

TBT, XTBT, NTBT was a series of Bart 2 band EQ's IIRC. I've used the TBT & NTBT and like them a lot. I don't know what the X in XTBT designates.

[VifferMike]

Thanks for the info, Penguin. Anyone else have any insight? Any Zon aficionados out there (I know you are ... )?