LABORATORY TEST REPORT
Newport Test Labs measured the output voltage of the NA 6005 at just over 2 volts, as shown on the tabulated chart, which is more than sufficient to drive any device it might reasonably be expected to be connected to. Channel balance was excellent, at 0.048dB, and the separation between the channels equally so, with a best result of 140dB at 16Hz. Channel phase was outstandingly good, measuring 0.02° at 16Hz, 0.01° at 1kHz and just 0.31° at 20kHz. Group delay was typical at 180° and 5.27°.
The Marantz NA6005’s frequency response was also excellent, just 0.09dB down at 16Hz, and only 0.32dB down at 8Hz. At 20kHz response was only 0.02dB down. You can see the graphed result in Graph 10. Newport Test Labs’ results show that unlike many manufacturers, Marantz is still including de-emphasis circuitry for those signals that require it, and that the circuit provided is extremely accurate, being only 0.001dB out at 1kHz, 0.011dB out at 4kHz and 0.114dB out at 16kHz.
Overall THD+N at 0dB was very low, at 0.011% as shown in the tabulated results. Distortion at 0dB, as well as at lower recorded levels, is shown in the accompanying graphs. Graph 1 shows the harmonic structure of distortion at 0dB. Other than a single even-order harmonic at –110dB (0.00031%), the harmonics are all odd-order, with a third at –120dB (0.0001%), a fifth at –108dB (0.00039%), and a seventh at –122dB (0.00007%). Higher-order harmonics are visible, but are more than 130dB (0.00003%) down. The signal at 15kHz is at –118dB (0.00012%) appears to be a sampling-related product rather than a harmonic. There’s a very slight rise in the noise floor around 20kHz, but since it’s more than 120dB down and occurs at such a high frequency, it’s of no importance.
At –6dB, almost all the distortion components disappear, with the ones remaining being the second harmonic at –126dB (0.00005%), the third at –112dB (0.00025%), and the fifth at –127dB (0.00004%), showing that the distortion components at 0dB were probably in the analogue output stage, due to the high output voltage, rather than related to the digital-to-analogue conversion.
The Marantz NA 6005’s frequency response was also excellent, being just 0.09dB down at 16Hz, and only 0.32dB down at 8Hz.