Panasonic CYPA4003U 1000W 4-Channel Power Amplifier ( Refurbished )

The amplifier also offers an "intelligent" bass servo circuit that adjusts to the limitations of traditional woofers. Compared to most midrange and tweeter drivers, woofers have a larger mass, heavier voice coils, and more inductance, thus they need more current to start moving. The increased current often causes the bass to lag behind the mid and high frequencies, resulting in unnatural tonal coloration. Furthermore, because of their longer throws, the woofers' voice coils have a tendency to deviate from pistonic motion, resulting in nonlinear dynamic distortion. The CY-PA4003's bass servo circuitry overcomes these shortcomings by feeding high current to the woofers at the moment of startup and instantaneously detecting and correcting the voice coil movements. This maintains the pistonic motion and linearity while helping the bass synch up with the rest of the frequency spectrum to produce a more authentic overall sound.

Though the CY-PA4003 is designed to drive four speakers, listeners can also bridge it for three-channel (two speakers and a subwoofer) or two-channel output (stereo), depending on their needs. To make the sub option more optimal, the amp also includes a low-pass filter that adjusts the cutoff frequency continuously from 50 Hz to 250 Hz. As a result, it's easy to upgrade to a subwoofer system that matches your speakers' low-end frequency limits.

Finally, the amp includes line-out jacks for easy expansion. The jacks let you connect multiple amplifiers--a must for power-obsessed listeners--while still keeping the wiring neat and tidy. Other features include gold-plated speaker terminals, a thermal shutdown protection circuit, and blue illumination. The amp measures 13.12 by 2.44 by 11 inches (W x H x D)

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