TUBE REPLACEMENTS
The Premier Four uses twelve vacuum tubes of three different types: two 5751 (V1
and V2), two 6FQ7 (V3 and V4) and eight EL34s (V5 through V12). Each type has
been carefully chosen for its circuit application. It is well known that tubes of a given
type vary sonically depending on the manufacturer. We have chosen the brands of
tubes that we supply based on extensive auditioning of available brands. The choice
of brand has been made solely on the basis of sonic performance and reliability
without regard to either cost or prestige. We know of no vacuum tubes available
which will improve the sonic performance of your Premier Four. Also, the tubes in
your amplifier have been tempered by a controlled burn-in procedure that permits
them to perform for a greatly extended period without sonic degradation. We
anticipate one to two years of operation without degradation in normal use. We
highly recommend that, when the time comes to replace the vacuum tubes, you
purchase replacement tube sets from conrad-johnson design.
The Premier Four has been designed to make tube replacement as simple as possible.
Because the output tubes are individually biased, replacement tubes need not be
matched pairs. No a-c balance adjustment is necessary. It is necessary to re-bias the
amplifier when the output tubes are replaced. The Premier Four has built in bias
indicators so that no instruments are required to make this adjustment.
