Tube amp question

Thanks @atmasphere that clears it up. I have done enough research to understand the parts of the tube so what you say makes sense to me. I appreciate your thoughts. BTW, I have to say I am intrigued by the new class D unit. Thanks again!

So @daveyf are you saying the 500v plate voltage is not enough to realize the full potential of the tube? If that's the case then why does Black Ice indicate they will work? I'm not taking sides with anyone, just trying to learn. May the debate continue!

Just a little more background here. The amp came with the EH EL34's. Having read a lot about the Genelex Gold Lions, I decided to give them a try (same EL34's). The sound quality was improved and I really liked them but they seemed to lack a bit of dynamics that I'm looking for. I am driving a pair of Legacy Audio Signature III's which are 4 ohm and 93db sensitivity. I'm looking for a bit more kick from them that I know they can provide.I purchased a quad set of KT120's and after allowing them to warm up, I biased them at 50mv per the manufacturer spec. I slowly raised the volume and after about 10 seconds the amp shutdown in protection mode. I emailed the factory and they believed that I must have a bad tube. This happened just after the Russian invasion of Ukraine and the run on tubes. I could not locate another set of KT120's anywhere. As I researched more I stumbled across a guy who had four remaining KT150's that are actually ARC matched. I am waiting for those to arrive. It will be interesting to see if the amp reacts the same or how it will perform. This damned Russia thing happened right in the middle of my experiment. But I don't at all want to devolve the conversation into politics. I appreciate everyone's insight

Thanks, I'll see how the KT150's shake out and I may consider that.

Thanks Atmasphere! this is from an email directly from Jerred at Black Ice...

@boomerbillone  Thank you for the insightful explanation!

I just wanted to close the loop here. I received the KT150’s yesterday and carefully installed them, I turned the amp on and allowed them to warm up and adjusted the bias (which took minimal adjustment) then let it settle in for several minutes, started some music and s-l-o-w-l-y raised the volume. They worked just fine. Not only did they work fine but they sounded great right out of the box. I could tell the music had more authority over the entire audible spectrum. I was very taken by how clean they sounded and the level of detail.

I had some work to finish up so I sat typing on the computer listening to Tubular Bells that randomly came up. Near the end of the piece Oldfield introduces the different instruments. The first time he spoke I nearly jumped out of my skin because his voice sounded so real. There was someone in the room with me! I only have about an hour or so on the tubes but already they are sounding fantastic! I don’t know if I am indeed getting everything out of them, I’ll let that debate rage but I sure do enjoy what I’m hearing!

I absolutely asked Jerred. That was the response I posted earlier in the thread.