No, Eldartford, the person saying that attaching an 8 ohm speaker to the 4 ohm tap will cause distortion because the tubes will 'see' a different impedence than if the speaker were attached to the 8 ohm tap, is wrong! When in doubt, use the lower tap, the worse that will happen is a loss of ultimate power transfer, but with lower distortion.
Respectfully, Bob P.
Respectfully, Bob P.