Match,
From what you say here and in other threads, it seems to me you may or may not hear the new tube. Not hearing much with changing rectifiers, cables, other tubes, vibration, etc, may not, but seems to indicate more foundational things.
It is not a question of whether rectifiers can be heard in Decware. They can if there is not something stopping the amp/system/room from its revealing potential. The question seems more, why can’t they be heard in some systems and rooms, and perhaps, by some folks.
Is my memory right(???), that you have to put your watch across the room to sleep? If so, it would seem your hearing may be pretty good, implying more system/room imbalances causing subtler things not to be audible???
In my case, my right ear drum burst a few times from infections growing up, and it does not work as well as the other. But I can hear pretty subtle changes in my room. Having played a lot of mainly acoustic music, and worked a lot to perceive subtle things...maybe I learned to compensate for my weaker ear.
Looking at why a rectifier might or might not be heard in a given amp, with Decware's pretty essential designs, if the amp/room is set up to reveal the amp's full potential, and if it is at the source, everything I have explored can be heard, IEC inlet/fuse to RCAs out.
Also power and cables, etc before the amp effect the rectifier sound. And since the rectifier’s electronic characters and sound effect everything after it….tubes, coupling caps, signal wires and so on,
if the system/room can reveal it, the rectifier is a big deal.Alternately, if something causes distortions, the distortions will be heard from whatever point on, damaging the whole, and accentuating other noise issues as it goes....Or if something solves distortions, everything from there on will be cleaner/more revealing.....
Even a really heavy power cord or speaker cable can throw things off. Using the same materials as a smaller one, a giant cable, especially with single conductors, will bring out more/thicker bass. And excess bass, along with room issues, masks subtler areas of the sound.
Likewise, excessive voltage from the house could notably contribute to other problems if the voltage is high enough to over-thicken/darken a Decware amp’s sound. And all the other things ...room, power, noise, speaker placement, vibration, cable qualities and tendencies, etc, etc...individually and collectively, they all matter collectively improving or degrading sound potential.
In my room, even different IEC inlets effect the sound in pretty discernible ways. More powerful, bypassing the Torii power supply caps can notably clean and refine the sound. Each cap works with different tubes, transformers and chokes....and though bypass caps reveal themselves differently in the power supply, these little cap signatures can be heard as, or more clearly than using them on my tweeters, or from changing coupling caps.....
By refining the power to the rectifier, the rectifier refines. And what the rectifier gives effects everything that follows. Point being, that this simple amp design is powerfully revealing all along from cables in to cables out, that is if it is not somehow limited.
But even if the power/source/amp and wires are relatively clean and balanced, speaker/room interactions can really hurt, right?
To try to get things on track to hearing more, might be worth exploring speaker placement and toe again? Even in an untreated room, you can at least mitigate many problems caused by how waves in whatever frequencies bounce around. If they overlap, there is attenuation or amplification that can set up serious balance issues. Whereas, minimizing room/speaker interaction issues minimizes funky frequency spectrum problems, revealing more system/room potential.
And the more you can hear, the easier it is to identify ways to improve the sound.
BTW, an RCA 5U4G can be many things. There are 5U4GB (straight side bottles) of different heights and vintage, and there are 5U4G-ST (coke bottle shape) of different vintages. The B and ST sound pretty different, and the variations within each type also sound different.
Here is a nice chart on the electrical qualities that contribute to characteristic sound influences of rectifiers:
http://www.300guitars.com/articles/rectifier-tube-voltage-drop-chart/