Uncompromised power supply
In any pre-amplifier, the power supply is a
sensitive and significant component. This is especially true when dealing
with phono levels. That’s
why the PL-P power supply uses a set of rechargeable "D" cell
batteries, operating through an external current charging AC
supply. This design eliminates all disruptive effects of AC powering from
wall outlets and may solve persistent hum problems. The internal power
supply regulation circuitry of the PL-P uses proprietary, dual DC-to-DC
converters to eliminate power supply ripples and assures a clean power
source for all active electronic stages and components.
Unique design phono stage
The phono stage is built around the
best tubes out of our selection and especially designed Nagra transformers
for impressive noise figures, dynamic and high-resolution performance
with both moving magnet and moving-coil cartridges.
Variable capacitive (from 47 pF to 837 pF) and resistive
(30 Ω to 330 Ω) loading is provided to allow
ideal matching with most available cartridges. Switches for
selecting the appropriate loading options are internally
mounted on the circuit board to protect sensitive low-level
signals from undesirable interferences.
A class tube
Two triode sections, biased for pure class-A operation, are
implemented in each channel for additional amplification. The PL-P has
two stages, the first one for level input management and the
second for output level management and record loop.
As in all vacuum tube circuits
within the PL-P, precise DC filament voltage regulation from
the power supply ensures low-noise, high-resolution performance
and a long lifetime. The output stage vacuum tubes, operating
in pure class-A, are directly coupled to the output connectors; they can
accommodate loads as low as 600 Ω. To facilitate tape transcriptions
and external signal processing, a full tape loop facility is also provided.
Input selection is made on the left side of the front panel
using a precision rotary switch. One phono and three line level inputs
are provided. Input levels for all sources can be adjusted via left and
right potentiometers on the front panel. A clever geared clutch mechanism,
allows these channel adjustments to be made either independently or
Attention to detail
To reduce unwanted interference, the main
circuit board is mounted on elastomer dampers to eliminate
the effect of external vibrations.
conserve component life and battery reserve, only those vacuum
tubes required for the selected input are turned on. The audio output is
automatically muted when switching between input sources.
Level matching through the Nagra modulometer
A highly precise,
Nagra-made modulometer, identical to the legendary NAGRA IV-S,
provides a multitude of functions through two coaxial, internal pointers
representing the left and right channels. The Nagra modulometer is a true
measurement device that allows precision over a large scale. The modulometer
can be used to adjust the volume and balance potentiometers for:
- Reaching a proper balance between left and right channels ;
- Compensating the level differences between various recordings
- Controlling the power supply DC input level ;
- Controlling the output level of the amplifier (if correctly