Smooth treble

the bright, brilliant and super transparent treble many people want when they are making the transition from "mid fi" to "high end" audio

Agreed. However, I would replace "super transparent" with "super prominent".

Smooth does, of course, mean there is no jagged & annoying response in the region of 4-9kHz, usually mistaken for "transparency"... as in, "wow, a veil lifted and my jaw fell through the floorboards". I've heard that said of a sibilant set up. Regards

Smooth means not course or irritating during extended listens.

"How can one get this smooth and refined high frequencies without severe treble roll off? "

For me it was a progression of things , of course the recording is the number one component .

I started by ditching metal tweeters in favor of soft dome or organic tweeters . As mentioned above ribbons will fall into this catagory as well .

I then ditched my SS CDP for a tube unit .

Then I ditched my SS amplification for tubed .

And finally finding a tubed int. amp with good top end extension .

It was a process of changes that taught me things along the way . This is not the only way but it is the way that works for me . And other things were accomplished along the way that increased my listening enjoyment .

While I believe that the smooth treble aspect can be accomplished with metal tweeters and SS components , it may come at a greater cost and may or may not give you the desired overall sound that pleases you .
For me it did not .

Good luck .

It is all to do with waterfall...driver resonance is what messes up treble. Soft domes treated with damping material on the fabric work well.

It is often a fight between on one hand stunning brochure quality frequency response plots versus a not so perfect treble rolled off above 12 Khz. If you let the frequency reponse plot dominate your design choice then you inevitably end up with a metal or very stiff type tweeter and that is how you get a waterfall with resonance.

Most people know as a rule of thumb that soft dome tweeters are smoother than metal ones...now you know why.

I did similar to Saki but for the purpose of changing the sound overall based on what I had heard auditioning various reference systems. I did not find the treble per se on my particular system with SS gear problematic at all though. When it occurred it was usually on certain (soft dome tweeter by chance) speakers with certain recordings in a certain room.

I "ditched" the SS pre-amp only because a) I need a SS power amp to properly drive my speakers and b) I want as few tubes in my system as possible in order to minimize maintenance and c) tubes in power amps are probably the most finicky and expensive.

So you can achieve smooth treble with SS as well of course.

A single tube in a tubed DAC is a good place to start if your issues are mostly with digital sources. Next step would be the pre-amp and finally the power amp if you turn out to be so brave.