is it ok to leave a tube amp on without speakers connected

Maybe this one worth reading

Like others report: My research indicates the voltage builds up and damages the output transformer. I wanted to disconnect one speaker so I could do the Soundoctor.com trick to integrate my sub. Was told never run tube amp without load (by Upscale guys) but you can use a 10 ohm 10 watt resistor in place of the speaker https://amzn.com/B0087ZD6FQ. I think they do that when they are working on an amp and connecting a speaker is inconvenient. Decided for my purpose I could just disconnect the input from one amp channel.

What does the manual/manufacturer suggest or warn against or not. It's a yes and no answer. My Cary Rocket 88R  does not need to see a load and will not damage the amp by design.  Others will require a load to be safely used and not damage the output trannies.  Never follow the advice of anyone other than the manufacturer of YOUR product .

With tube amps the answer is NO!.you  will fry the output xfmr. SS amps may  be left on though however connecting and unconneti g spkr cables leaves you vulnerable to accidentally shorting the leads.

NO. NO NO NO NO NO. Had a pari of VTLs without my WATTS attached. Scared the color off me (I'm Hershey Brown colored). 

NO!!!!