[quote name='SubsonicSimpleton' timestamp='1505402649' post='3371671']
Hipshot make a detuner for double bass, have a dig around on the american forum, there was a thread a while back started by someone who needed low C for a musical type gig but didn't have an extension and couldn't afford one.
[/quote]
I have one of those. It works just fine. It is on the tailpiece so it is not a quick flick like on the headstock of a plank.