The Final Countdown

Top MD Recorder, Sony MDS-JA50ES

German Stereo Magazine, April 1997, pp 20-23.
by Reinhard Paprotka

Step by step, Sony has succeeded in making the MiniDisc cool. The last round has started, because for 3100DM the small disc is now able to produce the best sound.

Two years ago Mr. MiniDisc surprised us with the MDS-JA3ES. Thanks to ATRAC 3.5, the MiniDisc achieved the fine resolution of DAT, and only frequencies above 18kHz were a problem. Most Hi-Fi fans didn't notice this, but the MiniDisc's developers couldn't rest.

When Mr. MiniDisc -alias Tadataka Fujiyama- came into our office this time, you could tell by looking at his face that something had happened. The magic word is ATRAC 4.5, an improved version of ATRAC data reduction that, even with broadband music signals, now handles frequencies up to 19kHz, and for Noise Test signals that are not so critical, up to 20kHz. ATRAC 4.5 has been put into Sony's latest top recorder, the MDS-JA50ES, which is the successor to the previous top MD recorder.

Test Profile

Sony MDS-JA50ES, about 3100 DM.

The competition will have to measure their products in the future against the brand new MD recorder from Sony. The reason for that is the new ATRAC 4.5 with wider frequency range and also the excellent A/D and D/A converters. The construction quality is excellent and the external features are overwhelming. So is the 3100 DM price.

Stereo Test Result: Excellent ***

As another improvement concerning the new ATRAC, Fujiyama explained that noise had been reduced by 3dB through higher computational accuracy, which should help further realize the 20 bit resolution of the MiniDisc. Certainly this expectation leads to skepticism, because compared to the DAT, the MiniDisc uses only a fifth of the data. Through intelligent use of mathematical and psychoacoustic features, it is possible to increase the resolution in the ranges important for the ear (as was done previously with DCC), compared to the fixed standards of DAT and CD.

The 20 bit technique can of course only fully be utilized if the music to be recorded is also 20 bits in resolution. For digital copies, this would require the master tapes, which the usual Hi-Fi fan is not likely to have access to. But it is reasonable to believe that regular 16 bit CD copies also get a gain from the improved internal calculation accuracy.

There are also possibilities for improvement in recordings made over the analog inputs, and here Sony put into the new top MD the analog to digital converter of the DTC-2000 ES and DTC-ZA5ES DAT recorders. This 20 bit chip has, among the ones tested by us, unexcelled fine resolution and noise performance.

In the DAT recorders mentioned above, the excellent converter quality is achieved through Super Bit Mapping to the 16 bit storage format, so this is also data reduction, but in this case from 20 to 16 bits. Looking at it this way, the Sony MDS-JA50ES can be understood as a challenge to the 2 top DAT recorders, which is, we think, a very interesting outcome!

To check this, we conducted a hearing comparison between the JA50 and the ZA5, first just through the excellent digital to analog converter of the DAT recorder. This procedure is necessary to remove the influences of different D/A converters, and to be sure to only compare the A/D converters with each other.

Using music with low to medium dynamics, it was very hard to hear a difference between the two unequal candidates -- maybe Sony's high end DAT was a bit better than its MD colleague. In spite of this, a super result for the MiniDisc.

Of course we were eagerly awaiting the results of our hard tests, the recording of extremely dynamic music that only appears in rare pianissimo passages. Played with high volume, the DAT recorder made a better impression that was quite reproducible, although the difference was very small. The slightly more smooth and therefore less annoying DAT background noise had its origin not in the DAT or MD recording itself, but in the electronics built around the A/D converter of the JA50 and/or in an unrepresentative sample of the converter itself.

The DTC-2000ES as well as the DTC-ZA5ES have a preemphasis that can be turned off. (In the CD and DAT standard, preemphasis is a fixed high frequency boost that is automatically undone during playback. The advantage is an improved noise cancellation for the upper frequencies, but because of the reduced dynamic range it can only be used for music without extensive high frequencies, for example classical music). With the preemphasis turned on, the ZA5 was able to improve this advantage even more, which means that the DAT recorders are still preferable for noiseless recordings over the analog inputs.

As with Sony's previous top model, the MDS-JA3ES, we couldn't hear any reproducible differences for digital copies compared to the DAT. Still, we greet the improvement of the ATRAC frequency response to 20kHz, because firstly, you are on the safe side, and secondly, very young and non-disco damaged ears are still able to hear such high frequencies.

Even with extremely low volume music, no difference. Here we would have needed a test with a 20 bit master tape, which unfortunately we didn't have, and -as paradoxical as it might sound- the high resolution of DVD audio could be used as the source data.

Test Protocol


The measurements in the laboratory showed the JA50 to have very good frequency and noise characteristics. Although the 20kHz mark was not reached with our multi-tone test signal, the result has improved considerably compared to the previous ATRAC versions. Not only here, the best MD recorder up until now!

External Features

Also in external features the Sony is setting new standards. The excellent digital gain control which is now possible, the clever digital fader, and the switchable digital output. Professional machines don't offer more.


Top marks in sound were achieved for the A/D converter, the sampling rate converter, and the D/A converter. The digital filter can be switched for various Hi-Fi tastes.

To send a music signal recorded in 20 bit resolution to other digital components, the digital output of the MDS-JA50ES can be switched from 16 to 20 bits. The advantage is that therefore 16 bit devices are not fed with a signal cut by 4 bits, but with a 20 to 16 bit downcalculated signal. Fine, fine!

Now to the playback section of the JA50, which we haven't looked at yet. It is nearly identical to the Sony CD player tested in this issue, the CDP-XA50ES, and it has a switchable digital filter, with the four most important characteristics: standard, spline, plane, and analog type. For the digital to analog conversion, Sony uses the Current-Pulse method. The playback electronics have excellent sound quality in normal and low volume playback ranges. The rumble that was noticed in the test of the MDS-JA3ES has been removed, and the spaciousness of the new MD deck is much better than the ZA-5 DAT.

As the last component that is important for the sound of a digital recorder, we must mention the improved sampling rate converter that makes it possible to record 48 and 32kHz digital sources to 44.1kHz MiniDisc format almost losslessly. This feature can be used to record from DAT, DSR and ADR/DMX. The resolution of the converter was improved from 20 to 21 bits, which makes no difference in practice, because such converters have in principle a better quality than the other components. And of course here it is also true that a chain is as strong as its weakest link.

In addition to the improvements in sound quality, Sony introduced a number of new and interesting features. For example, for the first time in a digital recorder there is the possibility of also adjusting the input gain of digital sources. Starting from 0, which is the default, the gain can be adjusted on the digital level from complete silence up to +12dB over normal, which allows one to adjust music titles from different CDs. Super, because up until now this was only possible over the lossy analog input!

To avoid unexpected clipping, there is also a switchable ``no clip function'' that automatically reduces the gain by the amount the signal exceeds 0dB (the clipping point) and therefore prevents strong distortions. In the spirit of preserving dynamics, there are no additional gain controls after that.

Also, fade in and fade out of digital recordings as well as played back music is possible with the digital gain control, where you can choose different characteristics, namely linear, logarithmic and sine. This is also true for the automatic digital fader, and the fade in and fade out times are separately adjustable for recording and playback -- pure professional technology!

Picture captions

  • First for a MiniDisc recorder, the MDS-JA50ES has two optical and one coax input, of course switchable. But no coax output.
  • ATRAC 4.5 is represented through the new CXD-2537 chip.

For the automatically set track marks made at silent parts of analog recordings, it is possible to set the silence threshold and the required silence duration. And pauseless recordings can be regularly marked at 1 or 5 minute intervals.

Fanatic MD lovers will appreciate the improvement in editing accuracy, which has gone from 60ms to the present 11.6ms. Just to explain this to MD beginners, it is exactly the editing that is responsible for the fascination of the MiniDisc, allowing you to divide, combine, move and -without producing wasted space- delete music titles and passages arbitrarily. And all this within 1 second and up to 50 times per disc. [?? -eaw]

One feature that some recording freaks will really miss is microphone input. The MDS-JA3ES still had it, so such an input would have been good for the subsequent model too.

In spite of that, Sony's brand new top MD is definitely the new milestone in MD recording. Even more than that: through its extensive functions with clever and generally sensible features, it is the furthest developed digital Hi-Fi recorder of all - here the influence of Sony's studio professionals cannot be overlooked.

The sound quality has also been improved, on the playback side, even above the level of Sony's DAT recorder DTC-ZA5ES. Given this background we can recommend DAT only to real tape fans, and for the case where you want to remove even the last little bit of noise on your analog recordings through SBM (Super Bit Mapping) DAT.

During the last two years, Sony's Mr. MiniDisc has really made all honors for his ``name''. Congratulations to Tokyo!

Lab Report

Parameter Measured
Sound Quality
Frequency characteristics of the data reduction system:
Using multi-tone signals, upper cutoff frequency

20 khz
Recording over digital input (D/A converter)      
Frequency characteristics      
Maximum gain drift without pre-emphasis 0.2dB 1dB 0.2dB
Maximum gain drift with pre-emphasis 0.6dB 1dB 0.2dB
Square wave behavior Satisfactory
Distortion factor 400Hz at -60dB 0.23% 5% 0.2%
Alias distortion at -30dB <0.03% 1% 0.03%
Converter linearity, maximum drift 0.9dB 5dB 0.5dB
Converter monotonicity Good
Noise floor ``digital null'' 108dBA 88dBA 106dBA
Quantization noise floor at 400Hz / 0dB 95 dB 77dB 95dB
Recording over analog input (A/D converter)      
Frequency characteristics      
Maximum gain drift 0.2dB 1dB 0.2dB
Square wave behavior Satisfactory
Distortion factor 400Hz at -60dB 0.2% 5% 0.2%
Alias distortion at -30dB <0.03% 1% 0.03%
Noise floor 104dBA 86dBA 95dBA
Quantization noise floor 91dB 77dB 95dB
Practical Issues
Input/Output Values      
Input sensitivity 476mV 500mV 200mV
Input impedance 36kOhm 10kOhm 50kOhm
Output voltage left/right at 0dB 2.48V / 2.53V
Maximum channel drift 0.13dB 0.2dB 0dB
Output impedance at 20kHz 0.19kOhm 3.2kOhm 0.2kOhm
Sensitivity to vibration Very good
Mechanical operating noise Very quiet
Average access time 2.5 seconds
Dimensions 43cm x 13cm x 41cm
Warranty period 24 months

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