Australian Hi-Fi

Laboratory Test Report

- Steve Holding

Newport Test Labs first tested the Cambridge Audio Alva ST’s speed accuracy and measured the platter as running just slightly fast, recording around 33.51rpm, rather than exactly 33.33rpm. While this is a dierence, it will have very little eect on playback pitch, because it means a recorded 1,000Hz signal would play back at 1,004Hz. The measured result of the Cambridge Audio Alva ST’s speed accuracy test is shown in the histogram of Graph 1.

This is such a small dierence that even a person blessed (cursed?) with perfect pitch would not be able to detect it. By way of example, the closest music note to this frequency is C6 which has a frequency of 1046.50Hz. C#6, which is the semitone above C6, has a frequency of 1108.73Hz, so you can see that since it takes a 62Hz dierence to adjust pitch by one semitone, a 4Hz dierence is not going to be audible. The measured result of the Cambridge Audio Alva ST’s frequency accuracy is shown in Graph 2.

Speed variation (wow and flutter) was measured at ±0.04% according to DIN IEC 386 2-Sigma, and ± 0.03% according to DIN IEC 386 dynamic. When Newport Test Labs measured for wow and flutter at 33.33rpm using the Australian standard, the result was 0.04% RMS unweighted, with the result at 45rpm increasing to 0.07% RMS unweighted. This means that the result at 33.33rpm was better than I’d expect for a turntable at the Alva ST’s price point, while the one at 45rpm was about what I would expect at this speed for this level. The actual variations in real time for the two IEC standards are shown in Graph 3.

Graph 4 shows the harmonic distortion of the Audio-Technica AT-VM95E. You can see that the second harmonic is at –33dB (2.23%), the third is at around –48dB (0.39%), and the fourth and fifth harmonics are both down at around –57dB (0.14%). This puts overall THD at around 3.5%, which is fairly typical for a moving-magnet cartridge.

The frequency response and channel separation of the Audio-Technica AT-VM95E cartridge fitted to the Cambridge Audio Alva ST turntable are shown in Graph 5. Newport Test Labs measured response and separation using a pink noise test signal, which stresses the cartridge to its fullest extent, as it’s required to deliver all the frequencie­s across the audio band simultaneo­usly. Most other test authoritie­s use swept sine testing for these two measuremen­ts, which requires the cartridge to deliver only a single frequency at a time.

You can see that despite the severity of the test method, the AudioTechn­ica AT-VM95E cartridge performed very well indeed. The frequency response

(black trace) between 25Hz and 14kHz is ±2dB, while between 30Hz and 1.5kHz, it’s an even-better ±1dB. The response does roll off a little at low and high frequencie­s, but the overall normalized response is 20Hz to 20kHz ±3.5dB.

Newport Test Labs measured channel separation at 1kHz as 17.1dB, which is a lower result than I expected, since the Audio-Technica AT-VM95E usually returns results of around 22dB at this frequency. Since this was a review turntable, extensivel­y used by dierent reviewers, perhaps the cartridge had had a hard life. Channel separation was, however, maintained at around this same level almost right across the frequency band, diminishin­g only above 10kHz, which is an excellent result. Overall, the Cambridge Audio Alva ST turntable delivered excellent performanc­e in all of the tests conducted by Newport Test Labs.

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 ?? ?? THD at 1kHz (Audio-Technica AT-95E MM Cart).
THD at 1kHz (Audio-Technica AT-95E MM Cart).

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