[Chris]

Richard if you prefer Quad 306 then you have the choice to replace the Kel84, or may be a new set of valves, a change of cables, or possible change of caps. I bought some used power cables this week and found the fuse and plugs to be in a need of a clean, the sound improvement was easily noticed. Audio parts degrade and it's a slow process that we do not notice over time. You could easily noticed the different between the Quad 306 and Kel84 so your hearing is not so bad.

Chris.