As long as people know what they are getting there is no problem. I have tube equipment myself and enjoy the colouration that such equipment brings.
Ok, then we are brothers-in-tubes, so I hope you'll take my disagreement kindly
I do take issue with this sentence from the website though:
"With a particular interest in high efficiency speakers and low powered tube amplifiers, Ojas audio equipment aims to bring realistic, natural sound to the listener."
Ignoring the undefinable term of "natural" sound, if he wants his system to be realistic, i.e. faithfully reproduce the source signal, he should not be using tube-based amplification. Sounds great? Probably (mostly due to the speakers I would guess). Natural? WTFK. Realistic? No.
"if he wants his system to be realistic, i.e. faithfully reproduce the source signal,"
As I've pointed out many times when these subjects come up, accuracy ("faithfully reproduce the source signal") does not entail "realism." They are entirely separable. Most recordings are not realistic. If you play them on an accurate system, you will not get realistic.
As for "natural" as a sonic description, I don't see why that concept would be mysterious or hard to understand. It means, in the case of audio, "sounding more like X sounds in nature, in real life" vs "sounding artificial."
For instance, if you take a balanced recording of a human voice played back on an accurate system, you can play with EQ in all sorts of ways to make it sound "less natural." You can emphasize the sibilant region so they sound utterly electronic and colored, you can scoop out the warmth region to make them sound too thin and lacking body, etc. "Natural" is of course a reference to how the human voice tends to sound "naturally" rather than after having been altered mechanically/electrically/acoustically in a recording and playback scenario. Dialogue editors and movie sound mixers are working all the time to ensure dialogue "sounds natural" - restoring 'natural sounding' warmth when needed, dialing back exaggerated sibiliance, etc.
And of course each time you have to "fix" a sound like that, you are deviating from the original signal, which is just another example for how "accurate" does not equate to "natural" or "realistic" and in fact manipulating the sound can actually enhance natural/realistic factors.
So there's nothing odd at all about the idea that a deviation from accuracy can, in principle, enhance the sense of "natural" or "realistic" sound.
When it happens, does it always happen is certainly up for debate. And since very, very few recordings and playback systems would sound truly "realistic," and most references to real life will show compromises, it's reasonable people will differ on which compromises they find to sound "more natural."
I find, in my system, that my tube amplification tends to make recordings sound more "natural" and "realistic," especially the human voice. Someone else may disagree. But though I haven't heard the Oja system,
in principle I would not dismiss that certain tube amps with those speakers may sound more "natural/realistic" to my, and other people's ears.