Quicksilver and 6SN7 pre

kt88, I had a Belles 20A for a while and it is a bit dark sounding, more so with some NOS tubes like RCA blackplates. The pre just lack the top end sparkle imo. I have also had various 6sn7 preamps because I like this tube, big open sound. The AES AE-3 DJH for example sounds more open to me but does not have the strong bass your 20A has.

The red base ones are a bit overrated for sound. People like them because they are so ruggedly built. There are equally good options at a fraction of the cost. Take it from a guy that has had over 20 different brands/types in various preamps:)