SUNN 100S cab question

[jlukas20]

I have a 1968 Sunn 100s.  There are two cabinet outputs on the back, one for 16 ohms and one for 8 ohms.  Normally I would think this would be an "either or" situation but the 16 ohm output is labeled SPEAKER and the 8 ohm output is labeled EXTERNAL SPEAKER, leading me to believe this was originally sold as a half stack (with a 16 ohm cabinet) with the option of adding an 8 ohm cabinet.

So can I safely power a cabinet rated at 16 ohms and a cabinet rated at 8 ohms or do I have to choose one or the other?

here is a picture of the cabinet outputs on the amp



here is the link to the schematic for the 100s

http://sunn.ampage.org/site/schematics/100s.jpg

[Isaac]

No. You can safely power a 16 ohm speaker or an 8 ohm speaker, or two 16 ohm speakers, but not a 16 and an 8.

Sunn wired their output jacks such that, if you plug into the 16 ohm jack, it connects to the 16 ohm output tap on the output transformer. If you plug into the 8 ohm jack, it connects to the 8 ohm tap. However, the 8 ohm jack also contains a switch, so when you plug into the 8 ohm jack, the 16 ohm jack is also connected to the 8 ohm jack. The 16 and 8 ohm labels refer to total impedance, not just the impedance plugged into that jack.