How are McIntosh C46 tone controls different?

If you look in the manual pg 22 it shows the frequency curves for each adjustment. I think the highest frequency tone control is centered on 8 kHz. Some say that's whre the typical harshness is. In my experience it wasn't or at least it didn't tame what was bothering me. For someone concerned about highs I would suggest either the C45 or the c2300 (also pg 22 of the manual) which have standard treble single-knob adjustments. I ultimately went with a c2300 for the tube front end and found the treble worked well. The Mc gear already does a good job with highs and ultimatly I found I didn't use it all that much - maybe on no more than 10% of my recordings.

Yep, that's where I think the confusion lies. You can take a look at the treble response and see it doesn't really take off until above 5 kHz or so. The equalizer tone controls on the c46 are more for tuning room effects than adjusting the highs and lows generally. I was going to buy a c46 until I realized the equalization controls had a different intention than the single treble control.