Sonus Faber w/ Sonic Frontiers Power 1 - Impedance

4-Ohm taps and not too loud.
SF goes down to <3Ohms so you will eventually damage your tubes anywhay on higher volume levels.
Think of changing this amp for Manley(if you want to stick with tube gear) or add SS amp for bass(if you have bi-wired SF).

Tfk, as Raquel said above, I believe changing to 4 Ohms requires opening the chassis. I have a Power 1 and that's what the dealer told me the change involved. Is your Power 1 different? Does it have actual 4 and 8 Ohm taps on back?

fwiw--I haven't changed/rewired for 4 Ohms and am using on the standard (8 Ohm?) setting on nominal 4 Ohm speakers with no issues.

Hello, and thanks to everyone for responding. Unfortunately, and somewhat ridiculously, the POWER 1 amp requires de-soldering and soldering to change from the 8 ohm factory setting to 4 ohms. This pretty much takes experimentation out of the picture. I think I'll just make the change and see what happens. If I need to, I'll look into the Manley amp.
(With the POWER 2 & 3 amps, you don't need to solder. They have screw-down leads.)

Thanks again.

Tom