Just the man to ask the next question. My speaker switch is not an A/B selector. I need to push A on, hopefully after turning B off and visa versa. With 4 ohm 80's and 8 ohm 60's, if I accidentally had them both on for a second (or more), I wonder if it would damage (fry) that section of the 1909? My buddy calculated the mix of the 6 & 8 ohm impedances would yield ≈ 3.4 ohms.

If that sounds about right, I wonder if a short time of a load like that (by accident) would fry those channels.

Dave

"In theory, practice and theory are the same. In practice they're not."