I own several vintage Sylvania fat bottle 6CA7 and a pair of new production EH 6CA7. I run them in a self-biasing single-ended amp.
In my setup I much prefer the vintage tubes, I should add that this is not always the case as I like several new production tubes. The Sylvania produce a very rich sound, with great vocals, good (not great) high frequency details and a bit of warmth on the bass with good detail. Overall detail & definition is okay but not great, same for how big of a soundstage they create. Those slight shortcomings aside, they produce very enjoyable music. Natural sounding vocals, smooth highs, and warmish bass.
The EH were a bit less in almost every regard in my system. The bass was even warmer, too much so to my ears. Vocals and highs were smooth and listenable but the overall sound didn't draw me into the music. I can put in the EH and listen to my system casually for hours but never get drawn into the music. I consider them good for playing music as I go about my chores or when I'm online. Saving my better tubes for more critical listening.
I have read opinions from people who love the EH and have not found them overly tubby. People who have selected them as their "tube of choice" for all listening. Different rooms, different equipment, different preferences.
