Hi
I never said RCA invented beam tubes - just their implementation of using plates rather than critically aligned grids as Mullard did made the RCA tube a better tube with less distortion.
In simulations, UL shows a compression effect with greater input drive. I found this surprising since it goes against the name of the connection and how it has always been presented. In a guitar amp, open-loop UL sounds the best and likely part of it is this compression, but more the fact of the reduced Z-out from U - not as dark and floppy as open-loop tetrode/pentode mode.
In my experience, I found a distinct sonic difference between the two groups of tubes based on screen structure, as my previous post stated. Your experience may be different. From what THD measurements I can make, the beam-forming plate group exhibited lower THD in the same circuit compared to any grid-screen tube. You may want to argue that the OT Ra "was not optimal" for all the tubes? But that is not really an issue. The tubes were driven to only 1W of output in what was a 60W circuit. All the tubes work well with the same range of OTs over a wide range of supply environments and in this case,m the values were all very middle of the road.
When you listen to a neutral sound and then a bright one, you will generally prefer the bright one - i is a quirk of our brains or physiology. The brighter sound I believe requires a bit more processing in our brains and once we have made that shift we are "EQed" in a way for brighter sounds just at that moment. Going back to the neutral sound will give the impression that 'neutral' has become 'dull' or 'lacking in treble'. For this reason, it is difficult to make side-by-side comparisons of sounds for whatever the purpose may be.
I never said RCA invented beam tubes - just their implementation of using plates rather than critically aligned grids as Mullard did made the RCA tube a better tube with less distortion.
In simulations, UL shows a compression effect with greater input drive. I found this surprising since it goes against the name of the connection and how it has always been presented. In a guitar amp, open-loop UL sounds the best and likely part of it is this compression, but more the fact of the reduced Z-out from U - not as dark and floppy as open-loop tetrode/pentode mode.
In my experience, I found a distinct sonic difference between the two groups of tubes based on screen structure, as my previous post stated. Your experience may be different. From what THD measurements I can make, the beam-forming plate group exhibited lower THD in the same circuit compared to any grid-screen tube. You may want to argue that the OT Ra "was not optimal" for all the tubes? But that is not really an issue. The tubes were driven to only 1W of output in what was a 60W circuit. All the tubes work well with the same range of OTs over a wide range of supply environments and in this case,m the values were all very middle of the road.
When you listen to a neutral sound and then a bright one, you will generally prefer the bright one - i is a quirk of our brains or physiology. The brighter sound I believe requires a bit more processing in our brains and once we have made that shift we are "EQed" in a way for brighter sounds just at that moment. Going back to the neutral sound will give the impression that 'neutral' has become 'dull' or 'lacking in treble'. For this reason, it is difficult to make side-by-side comparisons of sounds for whatever the purpose may be.
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