Properly designed amplifiers take this into account. I have never experienced a problem running two 4Ω loads per channel on any of my power amplifiers - neither did I expect any!
Back in the day JBL wired their woofers such that a positive battery terminal to the positive terminal on the driver would cause the cone to pull back into the magnet. Usually the reverse is true.
But what would you know? You were too busy saving the planet from the Mekon!
Keep safe and healthy!
I've read about the lack of support on my side of the Pond. It's sad to hear it's universal. The only way past it is for folks to quit buying their products. Good support policies are what leads to fresh sales. I certainly wouldn't buy a Mark Bass product.
Nobody has said that the pairing of different cabinets cannot work. It can and does. The caveat though is that luck is involved. They might meld harmoniously or fight each other all night long. For example if the cabinets are wired with differing polarities one will be trying it's best to cancel the other out and vice versa. Identical cabinets always work well together.
If none of the controls affect the signal from the send then the loop is pre preamp. Probably to allow the use of instrument level effect pedals rather than the line level most loops work at.
The 7027A is essentially a 6L6GC on steroids. The problem that has appeared with the demise of many tube/valve manufacturers is that you're never really sure what characteristics the device had been built to.
Hey Scouse, In the latter years of the Sixties I played the Cave often as a member of Earl Preston's Reflections. I met my wife playing in that band in a place called Nalgo somewhere off Queens Drive.. LOL
A few years ago one of my brothers took us down to the Cavern and I thought I was going bonkers. The club was in the wrong building and where it was was gone!!
I hope you and yours are keeping safe. The eldest brother is working his way through this damn virus but is getting better every day I'm happy to report.
My amplifier consists of a 2KW capable Class D stereo power amp driven by a little tube pre-amp that I designed and built for it. Into the two 4Ω Acme B2 cabinets, one on each channel, that I usually use it delivers a tad over 500W on each channel. Into all four of my cabinets it's the full 2KW.
My mother used to tell the tale of when I changed the plug on her iron. I was nine at the time and she didn't dare plug the thing in until my dad came home and checked my work. It was safe and properly installed! LOL
Change the plug for a proper 13A fused plug. It will save messing about later with questionable adaptors.