I guess this is the right place

I bought a new amp, a marshall JCM900 with a 1960 4x12 Marshall cab

I'm wondering what's wrong with it,s because whewn I plug the patch cable into one side or the other- there's a mode jack and an impedance jack, and they plug into the cab, which one side iays 4(16) and the other says 8- if I'm not mistaken but it seems if I plug it into the right side, it only comes out that side and if I Plug it into the left side- well it chooses the left side,.

It says to use only one input, on the cab, and I don't know what to do. Unless maybe I'm just deaf and I don't hear it correctly

also I'd like to know the difference between the mode (high and low) and the imedance input jacks on the back

And we will weave in and out of sanity unnoticed
Swirling in blissfully restless visions of all our bleary progress
Glowing in radiant madness
Well I believe there's 4 speakers per cabinet, so the 4 and 8 thing might be the difference between a half and a full stack.

Second, I wouldn't be F'ing around with a 1960 marshall cab without knowing what I'm doing.

Instead of asking little kids on an internet forum and blowing up your amp from their advice, look it up online? Maybe Email marshall or ask on the marshall forums, that'll probably be a better place.

Wish you luck