Using 4 ohm tap or 8 ohm tap

[leok]

kajh,

Interesting point. I hadn't realized that the autoformer outputs on McIntosh ss amps had impedance taps. As with tube amps, changing the tap will change the impedance "seen" by the output drivers (transistors in your case) as well as the amp's damping factor or output impedance seen by the speaker. It will also change, as was noted above, the output amplitude. But one assumes you have output amplitude to spare so that's not an issue.

I'd try the 4 Ohm and even the 2 Ohm taps. Two things that I can think of may be improved or made worse by the change: 1 is the amp's crossover distortion, which would be harshness in instruments like violins or exaggerated, unnatural sounding sibilances. This would be as the impedance seen by the output transistors moves toward or away from an ideal impedance at which they are the most linear in the crossover region. 2 is control over bass: lower Ohm output taps will generally provide tighter, better controled bass.

Try them all for a few days each and see which is best for your speakers.

Leo