Is there any 50W 300B SET monoblock out there?

deHavilland make a 40w GM-70 based SET.

@Ait- Unless that's a 300B on steroids; you didn't answer the question. Nice job though!

I am using a JAS array 2.1. a pair of sofia 300bs driving a pair of 805s yielding 45w of class A power. It runs hot (a small muffin fan keeps things cool)but it has that 3d holographic midrange and will drive 4 ohm loads. It has a passive preamp built in but I'm using the power amp section only driven by my Tranquility DAC using Audirvana plus attached to itunes in my Mac Mini, tons of gain and dynamics galor driving my Audiokinesis Prizmas.

Allnic makes 25 and 50 W 300B SET monoblock's.

In order to produce more power in a SET tube, the potential difference between the cathode and anode has to increase. When this voltage goes up to a point, the tube will start to emitt other radiation such cathode ray, ie electron. Higher still, it will emitt x-ray. I am a radiologist so I know.

There is legal restriction to control this type of potential X-ray tube. No one want to have x-ray examination while running his up power SET amp. That's why.