I've put the switch in, connected my cd player, bluetooth and turntable to the switch, took the output to the input of the bose active equalizer then the output from it to the amp as AUX input. I put a massive attack CD into the cd player and spotfied the same song and timed it with the cd then switched inputs. Can I tell the difference, NO, can an elecronic measuring device, likely yes, but do I care NO. The only impurity I can hear with my ears are the glasses in the cupboard shaking.
All these Bose 901 detractors, go somewhere else, this forum is for those like me who have acheived what they desire, we are all different, have different tastes, sight and hearing.
Tomorrow I'm going to buy either the NAD c399 (four channel) or the Purifi driven, D class NAD C298 (two channel) to drive my four 901s.