The tube ST70 is still the most trouble free amp I own. The tube PAS2 preamp lives in the attic, banished for its 100 times greater power use than the disco mixer. That way I can leave volume up on all three, LP turntable (magnetic phono cartridge), FM radio, and CD player, and when changing from one to the other, not walk around the piano to switch the inputs. When I'm using the tube ST70 amp, I mostly use a disco mixer (upgraded op amps and power supply) to drive it. Then an extra gain stage on your power amp could give you sharper slopes on the filters than passive filters, but not be extremely necessary. CD players, Radios, computers all put out that much voltage. If you are not playing LP's, 78's, or recording live music, then 1.6v PP input sensitivity for full volume is fine. You need about 50x gain for a magnetic phono cartridge or a little less for a dynamic mike.