Test of the portable MiniDisc recorders from Sharp and Sony
One for Everything?
German Stereo Magazine 8/97

Someone who wants to switch from compact cassette to MiniDisc needs 3 new units: a recorder at home, a player for the car, and a porti player to replace his walkman. All three together cost at best nearly 2000DM. If you choose a porti recorder instead you can cover all three needs with one unit - for only 600 DM. BUT: Does a porti recorder achieve the quality of a home deck?

The MiniDisc is the ideal media for portable use: small, robust, and enclosed in a dust protecting cartridge. In this respect the MD is ahead of the CD and is recordable as well. It's a small wonder that you can build complex data reduction electronics, A/D and D/A converters, and control chips into a case of the size of a walkman. But does the compact method of construction force the developers to compromise?

The Sony has the flattest case: The MD is slid into the guide slot of the opened lid and is placed directly onto the drive shaft when you close the lid. This principle was taken from the cassette Walkmans and allows the lowest case height. The Sharp porti uses a slot-in mechanism like the ones we know in home decks - this method requires more height to lower the MD onto the drive shaft. The slot-in mechanism is more practical and robust, but it makes the Sharp look more bulky. The width is determined by the width of an MD and the rechargeable cell that is placed beside it. Sharp and Sony have chosen a special lithium cell that is charged with the supplied power adapter and doesn't suffer from memory effects. You can also connect a supplied battery case for two drycells to the Sony portable.

Comparing features, the tiny MDs don't have to hide behind the home decks any more. They even have a microphone input and an optical digital input which can handle all three common sample rates. However, you need a special optical adapter-cable [TOS-link <-> optical miniplug? -eaw] that is unfortunately not supplied. Neither recorder has a digital output. When you record from the analog input you can adjust the recording level manually - with the Sony you also have the option of automatic gain control. The nine segment recording level meter is reasonable, but the Sony doesn't have an overload tag. However the MZ-R30 has a spacious display with a position indicator and simultaneous display of time and title information.

If you record digitally from a CD the track marks are copied correctly, but not the CD-text. Even if you copy from MD to MD the title and track information is lost - the music industry doesn't allow it. But Sharp has thought of a trick: After copying the music data, whoever wants to copy the text of the original MD must put the original disc into the recorder, this reads the information and stores it. Then the daughter disc is put into the recorder and the stored text is written onto it.

Both portis also have a memory for audio data: Its purpose is to maintain the data stream when the laser loses disc tracking due to heavy shocks. The Sharp stores 10, or in power save mode, 5 seconds of music. Both portis master even continuous vibrations astonishingly well, without perceptable dropouts. Only with regular jarring, which you get when you jog, do they give up after some time. Even if you are recording there is no "blur" as long as you don't overdo it with movements - important when you make interviews with your portable in your hand. The porties are suitable for journalists, especially the Sony with its automatic control of the recording level. But microphone recordings from both units aren't particularly noise free.

If you record from CD and play back over a Hi-Fi system, both tiny MDs achieve excellent sound quality - the Sharp recorder sounding better than the Sony. The Sharp already uses Sharp's ATRAC version 5.0 [This is in error, the MS200 is known to be Sharp ATRAC 4.0. -eaw] which transmits frequencies up to 20 kHz, the Sony uses the Sony ATRAC 4.0 chip. The Sharp also has an advantage over the Sony concerning noise and the clear playback of small music levels. It can nearly match the full-size MDS-JE500 deck. The fact that the Sharp can't reach the converter quality level of the full-size decks has its cause in the lower supply voltage and cheaper voltage stabilization. Nevertheless: an excellent result for a porti.
Sharp MD-MS 200
DM 600

An adequate MD recorder with a solid case that does its job at home and on the road. Its sound quality nearly reaches the sound quality of similarly priced full sized decks and it handles up to 20 kHz. It's only a pity that it has no digital output.

Sony MZ-R 30
DM 600

Thanks to ATRAC 4.0 now with a sampling rate converter. Good sound quality in recordings from CD - the converters don't reach the quality of the MDS-JE500 which has the same price. Very practical: automatic control of record level for microphone recordings. Dropouts from vibrations only in hard jogging.

Excellent: * * *
Very good: * *

Lab Report

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

20 khz

18 khz
Recording over digital input (D/A converter)        
Frequency characteristics        
Maximum gain drift without pre-emphasis 0.5dB 1.2dB 1dB 0.2dB
Maximum gain drift with pre-emphasis 0.4dB 1.0dB 1dB 0.2dB
Square wave behavior Very Good Very Good    
Distortion factor 400Hz at -60dB 0.3% 0.4% 5% 0.2%
Alias distortion at -30dB <0.03% <0.03% 1% 0.03%
Converter linearity, maximum drift 0.9dB 0.3dB 5dB 0.5dB
Converter monotonicity Poor Bad    
Noise floor ``digital null'' 90.5dBA 86dBA 88dBA 106dBA
Quantization noise floor at 400Hz / 0dB 89dB 82.5dB 77dB 95dB
Recording over analog input (A/D converter)        
Frequency characteristics        
Maximum gain drift 0.6dB 1.9dB 1dB 0.2dB
Square wave behavior Very Good Poor    
Distortion factor 400Hz at -60dB 0.5% 0.6% 5% 0.2%
Alias distortion at -30dB <0.15% <0.06% 1% 0.03%
Noise floor 90.5dBA 84.5dBA 86dBA 95dBA
Quantization noise floor 89dB 82.5dB 77dB 95dB
Practical Issues
Input/Output Values        
Input sensitivity 410mV 180mV 500mV 200mV
Input impedance 14kOhm 55kOhm 10kOhm 50kOhm
Output voltage left/right at 0dB 1.47V / 1.48V 0.76V / 0.76V    
Maximum channel drift 0.13dB 0.2dB 0dB
Output impedance at 20kHz 0.02kOhm 0.44kOhm 3.0kOhm 0.2kOhm
Input sensitivity 0.6mV 0.1mV 2.5mV 0.5mV
Input impedance 5.0kOhm 5.0kOhm 1kOhm 10kOhm
Resistance to Overmodulation 49dB 55dB 20dB 40dB
Noise Floor 65dB 65dB 65dB 80dB

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