Article Index
Dual MTR-75
p4 sound quality
p5 conclusion
p6 measured performance
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Rohde&Schwarz UPV spectrum analyse – phono stage measurement.



The needle of our Kenwood FL-180A Wow & Flutter meter swung cyclically and strongly around 0.25% wow (DIN, unweighted), exceeding 0.3% at times – close to unacceptable for a hi-fi product. No amount of run-in changed things. So this amount of speed variation was related to invariables such as mechanical eccentricity in main bearing or the platter’s belt rim. Our spectrum analysis shows the high variation lay at basic rotational frequency 0.55Hz (33rpm), eliminating the motor as the problem.  

   With DIN weighting, total Wow and Flutter measured 0.15% – a much better result because the DIN filtering suppresses variation at 0.55Hz. Speed was fast at +1.6%.

Subjectively, low rate variation like this makes for ‘watery’ pitch, softening time domain grip. Occasional slur, on sustained piano notes for example, may be apparent.

   The internal phono stage that provides Line output had a useful gain of x80 (38dB), giving a high 0.8V output from just 10mV input from a cartridge. This is more than enough to drive amplifiers to full output. Overload margin was adequate at 27mV in; few cartridges can deliver this. RIAA equalisation was very accurate and an excellent warp filter has been included, our analysis of equalisation accuracy shows here. Noise measured a low -70dB IEC A weighted, a respectable figure. 

   The USB digital output reached digital maximum (0dB) at exactly the limit of the fitted Audio Technica cartridge’s tracking ability, +15dB on CBS STR-112 tracking test disc (63µm peak amplitude). This was equivalent to 14mV in. USB has been well matched in.

   The ADC is 16bit resolution offering sampling rates of 44.1kHz and 48kHz. Noise measured a low -77dB IEC A weighted, the effective dynamic range of the ADC and a respectable figure for budget 16bit.

  The MTR-75 had poor speed accuracy and stability. The internal phono stage and USB digital convertor by way of contrast were very good, accepting they are budget items. The cartridge tracked well at 2.5gms and doesn’t need to be run at 3-3.5gms quoted in the handbook. NK



Speed error                   +1.6%

Wow                              0.25% 

Flutter                            0.08%

Total W&F weighted      0.15%



Hewlett Packard HP3561A – wow and flutter spectrum analysis.












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