3
possibility of ground loops forming between the two chassis, through the signal
interconnect shield and the ac line ground circuit, which can produce hum.
PS 2a Power Supply Connections______
If you purchased your
Phono 3
with the
Line 2B SE
line preamp and are sharing a
common power supply, you will be provided with the
PS 2a
power supply. The
PS 2a
power supply provides high voltage (B+) and heater voltage (A) for both the
Line 2B
and
Phono 3
preamps. It differs from the
PS 2
only in providing two power output jacks. The
physical separation of amplification and power supply units eliminates induced hum
originating from power supply circuitry and components. The
PS 2a
provides 12 VDC
(regulated) at 1.2 A for the tube heaters and 200 VDC at 20 mA for the B+ plate voltage.
Separate 4-pin jacks are provided for the
Line 2B
and
Phono 3
power connections via
special 4-conductor cables. Pin assignments are as follows: Pin 1: B–, Pin 2: B+, Pin 3:
A–, Pin 4: A+. In order to prevent a ground loop
from forming through the common B–
connections (signal ground), the B– feed for the
Phono 3
is isolated from that for the
Line
2
by a series 12 Ohm resistor in the power supply. In practice, either power output jack
can be used with either preamp.
Ch 1-2/LF Level
Out Gnd Ph2 Ph1
ON
OFF
Power In
12SC7
(L)
12SC7
(R)
12SN7
Power interconnect cable
AC Line cord
PSX Power Supply
