NuForce P-20

The  P-20 Preamplifier’s elegantly sculpted aluminum case encloses a number of  significant advances over the preamp’s award-winning P-9 predecessor in several  key areas, especially with respect to volume control. A preamp’s volume-control  capabilities are among its most critical features. In practical terms, we saw  room for improvement over the already excellent P-9’s volume control within the  areas of transparency and noise.
The  P-20’s numerically controlled, switched-resistor ladder network features the  last word in thin-film technology. In order to improve precision and lower the  noise floor to the vanishing point, we’ve implemented a single thin-film,  ultra-low-noise resistor in the signal path for each of the volume control’s  0.5dB gain settings, thus permitting the listener to achieve the desired volume  level in precise 0.5dB steps. As a further benefit, the listener is able to adjust  any input’s level to exactly correspond with any other, thereby simplifying the  matching of source-component volume levels.
The  heart of the P-20 boasts an all-discrete, fastidiously precise amplifier  module. Because speed is of paramount significance, we’ve reduced capacitive  loading on the final voltage amp with the implementation of ultra-low-noise,  monolithic dual JFETs, specially selected VMOS FETs, and extremely flat hFE  bipolar transistors in a dual cascode configuration, all of which are combined  within a driven-shield arrangement. The P-20 offers a 5MHz power bandwidth, an  S/N ratio exceeding 100dB, and a dynamic range in excess of 120 dB. There are  no capacitors or DC-servos in the inherently stable P-20’s gain circuit.
And,  in keeping with these advances, we’ve paid a great deal of attention to  isolation. We’ve covered the amplifier modules with thermal insulation along  with heavy copper shields in order to avoid thermal drift or signal-degrading  heating effects. Each amp module’s self-contained shunt regulator further  assists in isolation from power supplies. A similarly isolated floating-current  source supply feeds each module to insure separation from ground-system noise.
Since  all control functions are powered by discrete power supplies, the P-20’s design  prevents any logic circuitry clock-signal noise from ever contaminating the  analog section’s low-level signals. In keeping with the P-20’s state-of-the-art  features, we include a delightfully convenient, custom-designed remote control. In sum, the P-20’s  near-to-molecular clarity offers the last word in utterly transparent, organic  sound – in effect, a stress-free listening experience as close to live as audio  permits. Better still, these features can be activated by a 12V trigger signal  enabling system integration without the need for manual intervention. All  that’s required is a processor or receiver with a common 12V trigger  connection.

P-20 Measurement Results (Click to Enlarge)

Specifications

• Inputs: 1 XLR, 5 RCA
• Outputs: 1 RCA, 1 XLR
• THD+N at 1kHz = 0.0006% 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 : 17″W x 15″D x 1.97″H (2.56″H include feet)
• Weight: 17 lbs
• Power 120V 60Hz (100V and 240V models available)

Features