Ok, so I'm looking to daisy chain two cabs. One of them is a fixed 8 ohms, the other can be switched between 4 or 16 ohms. Can I safely chain these together? If so, at what ohmage should I set the head (4, 8 and 16 selectable) and cab (selectable between 4 and 16)?
Maybe. On the 4 ohm setting, the two cabs in parallel will be a 2.6 ohm load which only a few tube amps can handle. On the 16 ohm setting the parallel load will be 5.3 ohms, which should be safe to run on a 4 ohm tap. If your amp won't go below 8 ohms, then you'd be risking damage to the map.
What dystrust said. 16 ohms and 8 ohms in parallel will give you 5.333... ohms, which will work with an amp on its 4 ohm setting. Do not try the 5.333... load on the 8 or 16 ohm output from the amp, or you risk wrecking the output transformer.
What dystrust said. 16 ohms and 8 ohms in parallel will give you 5.333... ohms, which will work with an amp on its 4 ohm setting. Do not try the 5.333... load on the 8 or 16 ohm output from the amp, or you risk wrecking the output transformer.