2
Introduction _
The Mapletree Audio Design
Phono 3 Phono Preamplifier
is part of the modular series of
components that includes the
Line 2B
line preamp, the
Ultra 4B
phono/line preamp, the
LR 1
line router, and the
PS 2/2a/X
power supplies. The features of the
Phono 3
include:
? ?
Compact chassis layout and separate power
supply for low noise.
The
Phono 3
can
share one
PS 2a
power supply with the
Line 2B
preamp if desired.
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Exclusive use of New Old Stock (NOS) 12SN7 and 12SC7 octal tubes, known for
low distortion and musicality.
? ?
Low output impedance (<2.5K
?
).
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RIAA equalization within 0.5 dB, 50 Hz – 20000 Hz.
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Use of polypropylene film signal coupling capacitors.
? ?
38 dB gain suitable for all MM cartridges when used in conjunction with a line
preamp with at least 10 dB gain.
? ?
Selector switch for two separate phono inputs.
PSX Power Supply Connections_______
For operation with a separate line preamp or integrated amplifier, the
Phono 3
is supplied
with the
PSX
power supply, which provides high voltage (B+) and heater voltage (A+)
for the preamp. The physical separation of amplification and power supply units
eliminates induced hum originating from power supply circuitry and components. The
PSX
provides 12 VDC at 0.6 A for the tube heaters and 200 VDC at 15 mA for the B+
plate voltage. The preamp and power supply are connected by a special interconnect
cable that plugs into the 4-pin sockets on the rear of the two chassis as shown below. The
power supply chassis is connected to the AC line ground but is otherwise isolated from
the preamp chassis, which is connected to the signal ground. This eliminates the
PSX Power Supply
