Phono preamp tube rolling.

I have yet to hear any bit of kit made by Zesto that did not sound better than good and often great.

No significant sound differences rolling tubes in a clone of the EAR 834 phono preamp.

Tubes used: Bogen/Mullard, a Mullard ECC81 (in V3? The buffer stage, I believe), JJ, Brimar, Electrohome.

The 3 tubes in this preamp do not have to be matched.

KenRad VT231GT is also my favorite 6SN7.
ECC33 is not the same electrically as 6SN7.

Absolutely Correct about the ECC33, hence the advice given to myself to discuss this Tube with the 845 Designer/Builder.

It was Jaw on the Floor when the KenRad's were put into service.  
The KenRads and Sylvanias are both fine for ESL Speakers in my system.
The Sylvanias are a little too rich for my my tastes when used and the  Floor Standing Cabinet Speakers are in use.   

@pindar. I've paired a Kenrad VT231 Black Glass with a Sylvania VT-231 in my amp. Two very different tubes providing dynamic holographic sound.
And a Tung Sol BGRP in my preamp.