Also available are the SPAX7 Premium Grade Preamp Tube upgrade
for an additional $20.00
MESA SPAX7 preamp tubes are a low noise super-premium grade substitute
for any 12AX7 positions - They are a "Special Requirement Preamp Tube"
that possess an even higher standard of overall performance, due to
their incredibly low sensitivity to microphonic noise - This is the
ultimate preamp tube to use in all critical gain stage positions - It
is the absolute best of the best!