That single resistor is a feedback resistor. Altering this resistor from default setting to some magnitude may bring the amp onto oscillation or out of stability and another level of microphony(good point to check btw). The best what can happen is sacrificed dynamic range and transparency. I believe and know that tubes are not microphonic and amps/preamps are. There are plenty of good designed tube preamps with no microphony and my eyes and hands had seen them. Did anyone have an experience with AES by Cary little tube preamp?
As to BMW 5 or 3 series, in other than US countries people are still paying top dollar for these automobilles, but have still options not to have all extra items such as auto-trans, rear climate, auto-seat, power windows etc...
As to BMW 5 or 3 series, in other than US countries people are still paying top dollar for these automobilles, but have still options not to have all extra items such as auto-trans, rear climate, auto-seat, power windows etc...