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Cambridge Audio CD1 CD player Measurements
Sidebar 2: Measurements
On the filter 1 setting (fig.1), the response was essentially flat, measuring 0.2dB at 20kHz. On 2, the response fell away beyond 3kHz to 2dB, 20kHz. With filter 3, the output shelved just a little, this being the designer's preferred characteristic. On 4 (1 and 3 depressed), the bass rolled off early by 2dB into our low-impedance chart-recorder loading, while the high treble was slightly depressedanti-fuzz, perhaps? On 5, the treble rolloff accelerated, while 6all filter buttons depressedgave a maximum level of cut at both extremes.
Channel balance was excellent at 0.07dB, 1kHz; channel separation was also excellentworst case 105dB at 20kHz!as was the interchannel phase match.
The distortion results were fine at high levels (fig.2 shows the upband products for a full-level 20kHz tone), and were even better still at 60dB modulation (fig.3), as well as at 80dBFS, where the distortion of a 1kHz tone measured 27dB. This correlated well with the minimal level error at 90dBFS, which averaged less than 0.4dB, confirming true 16-bit resolution. The 90dB sinewave form (fig.4) was a bit noisy, but a reasonable shape may be seen underneath the noise.
The output is higher than usual at 4.3V, sourced from a low 110 ohms, which rose to a maximum of 4k ohms from the variable output.
The rejection of ultrasonic spuriae was unexceptional at a typical 53dB, but no problems were encountered with respect to error correction, de-emphasis, or mechanical noise. Electrical signal/noise ratios were excellent at 113dB or so. The impulse response (fig.5) showed a non-inverting, linear phase result.Martin Colloms
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