NuForce AVP-18 Surround Processor Test Bench

Test Bench

48 kHz PCM frequency response:
–0.26 dB at 10 Hz
–0.06 dB at 20 Hz
+0.20 dB at 20 kHz
+0.19 dB at 24 kHz.

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The above chart shows the frequency response for the AVP-18 at the preamp outputs of the Dolby Digital decoder. Left (aqua), center (green), left surround (red), and LFE (purple) channels at the preamp outputs of the Dolby Digital decoder. Left (aqua): –0.06 dB @ 20 Hz, +0.20 dB @ 20 kHz. Center (green): –0.06 dB @ 20 Hz; +0.14 dB @ 20 kHz. Left Surround (red): –0.07 dB @ 20 Hz, –0.15 dB @ 20 kHz. LFE: channel, normalized to the level at 40 Hz, is –0.04 dB at 20 Hz, reaches the upper –3dB point at 118 Hz, and reaches the upper –6dB point at 121 Hz.

There was no multichannel or other analog input to measure. The THD+N was less than 0.008% at 1 kHz with a 48 kHz/ 24 bit PCM input and the volume control set to “70”. Crosstalk with a PCM input was –102.93 dB left to right and –103.07 dB right to left. The signal-to-noise ratio with “A” weighting was –103.95 dBrA. —MJP

VIDEO

The NuForce initially passed our standard video tests with the exception that our original sample clipped all video information that was below-black (video levels 0-15) or above-white (video levels 236-255). Although this technically meets broadcast specs, elimination of headroom above 235, in particular, can cause a loss of detail in bright highlights on occassional scenes that nonetheless contain above-white information. (The inability to pass below-black information can make it more trickly to use test patterns to set display black level, i.e., the brightness control, but is otherwise benign).

By our print deadline for this review for Sound & Vision magazine, Nuforce had sent a new sample that partially corrected the clipping issue for RGB video signals and had another sample on the way said to fully resolve the problem for the more common YCbCr signal type. Our 5-star Video Performance rating in print was based on our confidence that this would be resolved, and we have confirmed that the subsequent firmware update did fully resolve any video clipping of either signal type. Owners of AVP-18s should visit the "Downloads" tab at the AVP-18 product page at Nuforce.com and insure they have downloaded firmware version "AVP-18_Firmware_02172014" or later. -Rob Sabin

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