VACUUM TUBES
The audio circuit of the PV7 uses five vacuum tubes of two different types: three
12AX7 (V1, V2 and V4) and two 12AT7 (V3 and V5). 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 without regard to
either cost or prestige. We know of no vacuum tubes available of the specified types
which will improve the sonic performance of your PV7. Also, the tubes in your
preamplifier have been tempered by a controlled burn in procedure that permits them
to perform for a greatly extended period without sonic degradation. We anticipate
two to three 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.
Please note: Substitution of 12AX7 type for the type 12AT7 is likely to damage the
12AX7. Other tube type substitutions may damage the preamp circuitry or
transformer.
