Hello, yesterday I called Keith Herron to talk to him regarding my VTSP 3A/360 preamp.
We talked about whether an upgrade would be useful, and Keith said no, the unit I have is one of the very early ones using six 6922's, and is built in a way that it would not benefit from an upgrade.
My thanks goes out to Oswaldo Martinez, who sold it to me. It's all he said it was, and I appreciate his honesty..
Regards,
Dan