Vacuum Tube Replacement - Conrad-Johnson PV11 Owner's Manual

BALANCE: This control is an eleven position stepped attenuator, ad-
justing the channel balance in approximately .75 dB steps. The maxi-
mum attenuation is under 4 dB, so both channels will be present even
in the extreme positions. In normal use the control will be centered.
LEVEL: The PV11 volume control is an extremely precise control, main
taining channel to channel accuracy to within 1/2 dB throughout its
rotation.

VACUUM TUBE REPLACEMENT

The audio circuit of the PV11 uses six vacuum tubes of three different
types: two 12AX7 (V1 and V2), one 5751 (V3) and three 12AU7 (V4, V5
and V6). The PV11L uses two type 12AU7 (V5 and V6). 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 we supply based on extensive audi-
tioning of available brands. The choice of brands has been made solely
on the basis of sonic performance without regard for either cost or
prestige. We know of no vacuum tubes available which will improve the
sonic performance of your PV11. 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 with out sonic degrada-
tion. We anticipate two or 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.
Consult the tube location diagram on the next page when replacing
tubes.
Please note: The indiscriminate substitution of type 12AX7 tubes for the
5751 will seriously degrade the sonic performance of the unit.
PV11 and PV11L Owner's Manual 7