Manual
8
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356 South Abbott Avenue, Milpitas, CA 95035, USA
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PHONE: +1-408-627-7859
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nuforce.com
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The NuForce P-9 Preamplifier
NuForce’s breakthrough P-9 Preamplifier is a low-noise, high-performance audio component housed in
two discrete boxes. One contains three power supplies and microprocessor control logic; the other, an
analog volume control, input selection relays and ultra-sensitive analog circuits. The boxes are similar in
appearance to our Reference 9 Series power amplifiers.
The P-9 features a
Dual-Drive
control mechanism. Changes in volume is achieved via a full-function,
custom-designed remote control interfacing with a digital volume control, or a manual Alps volume
potentiometer. A microprocessor drives the high-performance Alps motorized pot in the analog chassis. A
communication protocol feeds back the volume level to the microprocessor in order to synchronize level
settings on the digital volume indicator and Alps volume pot. The P-9’s volume control is ultimately
analog. As a convenience feature, the digital volume control acts only as an interface with the remote.
Built-in memory stores the last-used input selection and volume level.
The heart of the P9 features an all-discrete, precision amplifier module employing ultra-low-noise,
monolithic dual JFETs, specially selected VMOS FETs and very flat hFE bipolar transistors in a dual-
cascode design with a driven shield to reduce capacitive loading on the final voltage amp. These features
combine to achieve a 5MHz power bandwidth with a S/N ratio is excess of 100dB, and a better than 120-
dB dynamic range. The P-9’s exceptionally stable gain circuit has no capacitors or DC-servos in its signal
path.
In laying out our design, we paid particular attention to isolation from external influences. To avoid sudden
thermal drift or signal-related heating, the amp modules operate within heavy copper shields with internal
thermal insulation. Each amp module has a self-contained shunt regulator to increase its isolation from the
power supplies. Further, each module is fed from a separate isolated floating current source to further
isolate the amp chain from potential ground-system noise. The control system sends DC only to the relays
and the potentiometer’s motor. No logic circuitry with the attendant noise of clocks and fast edges
contaminates the analog section’s low-level signals. The P-9’s overall isolation achieves a remarkably low
noise floor while providing the convenience and ease of remote-control operation.
For the audiophile who wants to integrate a home theater system into an uncompromising audio system, the
P-9 offers a novel bypass system connecting the main speakers’ power amps to the AV processor or AV
receiver amp’s output, thus allowing for a seamless transition to THX multi-channel surround with bass
management. This feature enables integration without the need for hands-on intervention. All that’s needed
is a processor or receiver’s 12V trigger source.
Feature Summary:
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Two-box design
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Small 8-½” half-rack chassis
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Ultra low noise 1nV/
√
Hz JFETs
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Custom-made Alps motorized high-performance volume control
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Full microprocessor control with memory retention