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Preamplifiers
Demian Martin is a widely experienced industry consultant specializing in systems design covering electronic, electrical and acoustical products for consumer electronics manufacturers.
Martin has a long, distinguished history in the audio industry. He was Co-founder and Director of Engineering of Spectral Audio where he designed an impressive number of high quality and durable electronics products. He was responsible for the design and engineering of Spectral's very low noise preamplifiers including the DMC-10. He also designed Spectral's wide band power amplifier the DMA-100 Instrumentation Amplifier. The DMA-100 was six years in development and brought about a new performance benchmark in amplifier design. Many of the products that he designed while at Spectral have had a market life of over ten years. |
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NuForce P-9
THD+N = 0.0004% @ 1kHz and a power bandwidth of 5MHz. Near perfect reproduction of 125kHz square wave.
Housed in two chassis, the low-noise, high-performance Nuforce P-9 premaplifier is a breakthrough product. One chassis contains three power supplies and microprocessor control logic; the second chassis contains an analog volume control, input selection relays, and sensitive analog circuit components. Externally, the dual P-9 chassis are a stylistically consonant match to the NuForce Ref 9 Series power amplifiers.
The P-9's 'Dual Drive' volume mechanism can be controlled either by a custom-designed, full-function remote interfacing with a digital volume control or by the manual Alps volume pot. A microprocessor control drives the high-performance Alps motorized pot in the analog chassis. A communication protocol constantly senses and feeds back the volume level to the microprocessor to sync-up the level settings on the digital volume indicator and Alps volume pot. Primarily for convenience, the digital volume control acts as an interface to the remote control. The volume control is ultimately analog based. As an additional convenience, memory stores the last-used input selection and volume level.
The heart of the P-9 boasts an all-discrete, precision-operational amplifier
module. To reduce capacitive loading on the final voltage amp, the design incorporates ultra-low-noise, monolithic dual JFETs, specially selected VMOS FETs and extremely flat hFE bipolar transistors in a dual cascode configuration with a driven shield. All this is necessary to achieve a 5MHz power bandwidth, a S/N ratio exceeding 100dB, with better than 120 dB of dynamic range. The inherently stable P-9 gain circuit has no capacitors or DC-servos in the signal path.
Much attention has been paid to isolation. The amp modules are seated within heavy copper shields with internal thermal insulation to prevent thermal drift or signal-related heating capable of interfering with the preamp's operation. Each amp module has a self-contained shunt regulator to increase its isolation from the power supplies. A separate, isolated, floating-current source supply feeds each module to insure further isolation from noise in the ground system. The control system sends DC to the relays and the potentiometer's motor only. No logic circuitry with its clocks and fast edges introduces noise into the analog section's sensitive, low-level signals. While providing the custom-designed remote control's exemplary convenience, the preamp's overall isolation results in an extremely low noise floor.
For audiophiles who want to integrate a home theater system into an uncompromising audio system, the P-9 incorporates a unique bypass system that connects the power amps for the main speakers directly to the AV processor or AV receiver amp, thus allowing for a seamless transition from the most demanding audiophile performance to THX multi-channel surround with bass management. Better still, this feature can be activated by a 12V trigger enabling integration without the need for manual intervention. All that's needed is a processor or receiver's 12V trigger receptor.
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Feature Summary:
- 2-Box design
- Small 8 ½" half-rack chassis
- Ultra low noise 1nV/v Hz JFETs
- Custom-made Alps motorized high-performance volume control
- Full microprocessor control with memory retention
- "Dual-drive" volume control mechanism
- No capacitor and no DC-servo in the signal path
- 3 separate power supplies
- High-performance HT bypass integration
- Individual audio channels are shielded with heavy copper shield with thermal barrier.
- Solid stainless steel back connector panel forms a solid signal ground reference
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Specifications:
- Inputs: 5 RCA (including Home Theater bypass input
- Outputs: 1 RCA, 1 XLR (XLR output is unbalanced)
- THD+N at 1kHz = 0.0004% at 20-20kHz = 0.003% at DC to 1MHz: < 0.05 %
- S/N = 100dB at 20-20kHz S/N > 90dB at DC to 1MHz
- Frequency Response at 20-20kHz = +0.02dB/-0dB at DC to 1Mhz = +0.5dB/-0dB at DC-2.5 MHz +0/-3dB
- Maximum output: 7V RMS
- Phase shift = 0
- Input impedance = 10K ohm
- Output impedance = 100 ohm
- Dimensions: 1.75"H x 8.5"W x 16"D
- Weight:
- Power 120V 60Hz (100V and 240V models available)
Chassis available in black, silver or rose copper color anodized aluminum. |
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