[quote name='DorsetBlue' timestamp='1372838348' post='2130429']
I think there is a high end maker that uses them (can't remember the name). Found these on Thomann:
[url="http://www.thomann.de/gb/abm_6240_webster_nut_bass.htm"]http://www.thomann.d...er_nut_bass.htm[/url]
[/quote]
Those on my Warwicks have a different design. They comprise a flat, fixed base and a slotted top piece that's mounted on the base with two screws, which can be used to raise or lower it. High-end Warwicks have brass adjustable nuts, mine are humble plastic, but they work fine.
[quote name='Fat Rich' timestamp='1372841632' post='2130475']
Pretty much just Warwick as far as I know. Getting the nut height right isn't something that needs to be adjusted by the player, the builder should get it right when the bass is built. Some purists may feel that because the threaded bits of the Warwick adjustable nut aren't permanently fixed to the neck you lose some sustain / tone, but it's probably negligible.
I expect Warwick have trademarked the design and they're known for going after anyone who infringes anything of theirs very aggressively.
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To be honest, I don't see why adjusting the nut should be seen as less of a task that can be carried out by the player than, for instance, adjusting the truss rod or repositioning the saddles. I know that, on my Warwicks, the adjustable nut has helped me get exactly the right action everywhere, whenever I've changed strings from rounds to TIs to D'Addario Chromes. You don't get the same results, with the same ease, on other basses.