NuForce Reference 18 Monoblock Power Amp
All NuForce power amps are based on a design the company calls Analog Switching Amplifier technology. In this technique, a power oscillator is modulated by an audio signal to produce an amplified signal using a reconstruction filter without the bandwidth limitation of a conventional, fixed-frequency, carrier-based PWM (pulse-width modulation) control. The result is a nearly ruler-flat frequency response from 20Hz to 20kHz with a 1dB peak at 60kHz and a rapid fall off reaching -3dB at 120kHz as shown in the Audio Precision graph above.
Another innovation unique to the Reference 18 is NuForce's Cross Matrix Array (CMA) capacitor board, which arranges many capacitors of various capacitance values in a quasi-random pattern to spread the inevitable resonances across a wide range of frequencies. Also, the capacitors are positioned so that their polarities are reversed with respect to each other to minimize stray magnetic fields and thus parasitic inductance. This reduces the amplitude and Q (steepness) of the resonances and allows more of the capacitors' stored current to be used in the output, though it also requires a larger chassis.
The Reference 18 provides one RCA unbalanced and one XLR balanced input along with one speaker output. The available RMS (continuous) power is spec'd at 175 watts into 8Ω and 335W into 4Ω or 2Ω, while peak power (20msec hold time) is spec'd at 325W into 8Ω, 650W into 4Ω, and 1300W into 2Ω. THD+N is 0.01% at 1kHz, 1 to 10W, A weighted.
At $3800 each, the Reference 18 is not cheap by any means, but it's far less expensive than many other flagship monoblocks I've covered in this blog. I hope to hear it somedayit meets two of NuForce's three mission goals, so I have high hopes that it will thrill the ear as well.