The vintage Quad 405 is still a great sounding amplifier, combining the very best of Quads' legendary design skills and build quality. As with all old hi-fi though, the capacitors inside the Quad 405 will be getting pretty long in the tooth. Electrolytic capacitors really only have a lifespan of around ten to fifteen years, after which the electrolyte dries out, the esr goes up, and the all important sound quality goes down. This degredation in sound quality is so slow and steady, that the owner may not notice the change until it reaches a critical level. Simply replacing the electrolytic capacitors will rejuvenate your Quad 405. In fact, using todays high-quality components, your Quad 405 will sound better than the day it left the factory, and more than capable of showing many modern amplifiers a thing or two!
QUAD 405 UPGRADE - STAGE 1
Audio-grade F&T Cap Low-ESR/ESL SI power supply smoothing capacitors
Audio Grade Elna Cerafine capacitors
LME49710 National Semi Opamps
Additional PPS Opamp decoupling capacitors for reduced power supply noise