The L-5500 was designed by Paul Gagon and Steve Grom. Gagon was an employee of BBE sound when they acquired G&L, so the L-5500 is an in-house design, albeit by what was recently added talent at the time. Gagon is the person responsible for the recent development of the M-series electronics.
As I understand it, the 5500 was intended to give G&L a 5-string offering to span the gap between the L-5000(unpopular due to the very narrow string spacing - essentially 5 strings crammed into a 4-string bass), and the release of the L-2500. This information should probably be taken with a "grain of salt", as it is sometimes difficult to believe that G&L had any master marketing strategy in place, as some things in their lineup seem to originate without a clear "reason to be".
I've never had the opportunity to play one of these, but hope to do so at some point. Most every description I've heard or read says the sound is clean and massive and the build quality excellent. The word heavy is often used in describing these. The L-5500 can definitely be called the "Un-G&L G&L".
