Jimi Hendrix’s Guild Thunderbass Quantum Ampaccess_time First seen circa 1967
According to Dave Weyer used this amp during his early days with The Jimi Hendrix Experience, and apparently later on as a preamp [Jimi Hendrix’s Wah-wah Pedal and Amp in J. Levine’s New Year’s Day Auction ] To which extent the amp was used is unfortunately unknown, but it is likely that it didn’t play a major role in Jimi sound.
The story of how the amp was discovered is pretty interesting. User by the name “tubezarmy” posted on the LetsTalkGuild.com forums that he bought a Thunderbass amp at a pawn shop, and discovered that it had “J H EXP” stenciled on the bottom. Apparently, the person then sent the amp to Weyer (who is known for working on Jimi equipment), who determined that this was the exact same amp that he modified for Jimi in the late 60s.
Detailed photos of this amp can be seen here – Guild amp – Jimi Hendrix.