i know impedence is covered everywhere in the forum but i have read nothing for a stereo ext cab. can i use both 8ohm outputs and run them into a single cab that is wired in stereo? i.e. my marshall lead 900. that amp is switchable to mono 16ohm and 8ohm stereo. it does have two inputs. any thoughts?

My Crate 4x12 has the same options. Mine can be run in stereo at 8 ohms or mono at 16 or 4 ohms. There's also an Extension cab quarter inch jack on the mono setting. I have 4 16 ohm Vintage 30s in mine.

I'm also interested in how this works out. Would it be safe to run my cab in stereo on the 8 ohm settings using both 8 ohm outputs on the RV50?

I think safety says to me to run it in 16 ohms mono from the 16 ohm out on the RV50.

bump

Looks like the Dukes and Lords are too busy with OT discussions to answer this one...

Think of your stereo cab as either a single 16 ohm cab or two 8 ohm cabs.

Orange amps are designed to run a single 16 ohm cab from the 16 ohm output, or two 16 ohm cabs from the two 8 ohm outputs. Running two 8 ohm cabs into the two 8 ohm outputs results in an impedance mismatch which, depending on who you ask, may or may not damage your amp.

As Sooner says, you will mismatch the impedance. You would need to have 2x4 ohm outputs for that to work, but even if you would have that it would sound exactly the same as using one speaker cable to the cab as a mono cab.

Running two signals that sounds the same to two different cabs (or a stereo cab) won't make it stereo.