Tube Heater Voltage Jumper Settings
The MZ3 comes with selected
old-stock 12SN7 tubes as its
standard output tubes. By
changing the jumpers on the
circuit board, the amp can also
use 6SN7 tubes. These are
identical sonically, they simply
use different voltages for the
heater. When switching from
one to the other, be sure to set
the jumpers on the boards to
the correct position. A 6-volt
tube like the 6SN7 will burn out
quickly if given 12 volts.
On the circuit board, there are
two headers next to each other,
for a total of 4 pins. There is a small diagram showing the correct
way to orient the jumpers. When using only a single jumper in 6V
operation, there is a header labeled “park” where you can store
the extra jumper.
To use 6SN7s, set the jumpers to 6V by placing a single jumper
across the center two pins. To use 12SN7s, set the jumpers to 12V
by using two jumpers, covering all 4 pins.
Tube Replacement/Rolling: The amplifier operates the tubes in a
manner that maximize tube life and the tubes are expected to last
over 10 years of regular use. The sockets are tight, so gently rock
the tube pins until you are able to remove the tubes. We use high-
quality ceramic tube sockets with gold pins which are designed in
such a way that the white ceramic part may shift slightly. This is an
intentional design; the tube socket is very secure.
