Conrad-Johnson ET3 Preamplifier Owner’s Manual
9
Vacuum Tube Replacement
The line-stage audio circuit of the
ET3 Preamplifier
uses one type
6922 miniature twin-triode vacuum tube (V1) – note, (V2) is not
used in this model. Units with the optional high-gain phono stage
have three additional tubes – all type 12AX7 (V3, V4 and V5).
Units with the optional low-gain phono stage have two type 12AX7
(V3 and V4) and one type 12AU7 (V5). The brand of tubes we
supply has been chosen by first selecting those brands which are
known to be most reliable, then by extensive auditioning of these
acceptable brands with the final choices being made solely on the
basis of sonic performance. We know of no vacuum tubes
available which will improve the sonic performance of your
ET3
Preamplifier
. The tube in your preamplifier has been tempered by a
controlled burn-in procedure that permits them to perform for a
greatly extended period without sonic degradation, then selected
for minimum residual noise. Replacement tubes are prepared and
selected in the same way. Therefore, we highly recommend that
you purchase replacement tube sets from conrad-johnson design.
We anticipate tube life to accommodate two to three years of
operation without degradation in normal use - if the preamplifier is
switched off when not in use. If the preamplifier is left on at all
times, tube life can be exhausted in a matter of a few months.
