It simply may be that your vt-231's and the new wgta's have a relatively similar sound signature. Now if you had tried a tung sol 6sn7gt round plate or a Sylvania 6sn7w I believe you might hear a difference. Also however, one has to consider that some preamps are not so responsive to tube rolling as others. I have a deHavilland Ultraverve which relies on the 6sn7 tube. Each tube I try sounds unique and different and it is very apparnent each time I roll in a new type. I have tried about every NOS 6sn7 tube out there. I like the RCA vt-231 grey glass, the Sylvania 6sn7w, sylvania 6sn7gt, Raytheon 6sn7wgt...but for overall performance across the spectrum the Tung Sol round plates are hard to beat...at least for my pre...but they are expensive and disappearing quickly.
Tube Rolling - No Change in Sound
In my Wyetech Opal pre, I substituted NOS Ken Rad VT231's for JAN Philips WGTA's in the input stage, expecting more body and warmth to sound based on Ken Rad reputation. But nothing has happened; I perceive no audible difference from the switch in tubes! What's up with this? This was my first foray into tube rolling.
Neal
Neal