Best sounding 6SN7 VT231 for amplifier input

Define "romantic".....

For a VT-231.....

The RCA have a rich harmonic structure;
the Ken-Rad great bass and drive;
the Sylvania a wide bandwidth and excellent air;
the Ratheon are the sweetest;
the National Union have great midrange...

The most "balanced" of all these factors (and others) taken together is probably the Tung-Sol. I agree with DennisTM that this good balance/neutrality makes the Tung-sol a good preamp tube.

For the 6SN7W mentioned.... in addition to the metal base types, there are short and tall bottle 6SN7W tubes. The short bottle have better low level detail and the tall bottle more slam.

After trying out various WWII era Sylvania, RCA, and clear glass Ken-Rad VT-231s, I finally plugged in a newly acquired matched pair of black glass Ken-Rads and they have literally transformed my system.

They don't have the same top end extension as the Sylvanias, but I feel they have a more "correct" and liquid treble, lush mids, and solid bass. Bigger soundstage too.

My preference was the 6SN7W metal base, followed by the Ken-Rad and Tung-Sol black glass. The Mullard CV had a little higher noise floor, but very seductive and enveloping. When I wanted to simply float away on the music, the Mullard was a great choice; but just a little too romantic for serious listening. Enjoy.

The final choice of course comes down to your system and your personal taste. This list should keep you busy for a while! :-)

Sugarbrie, I think I got a set of Raytheons and Mullards around here somewhere...need to try them out too.