Sony MDS-JE640
A mid-line MiniDisc deck with a quiet spec sheet: 98 dB of signal-to-noise, and a headphone jack the cheaper sibling never got.
Overview
The number that jumps off the page is the signal-to-noise figure: over 98 dB during playback, measured by Sony's own manual. That is two decibels better than the MDS-JE440, which shares a chassis and a manual with it. The frequency response is quoted at 5 to 20,000 Hz, ±0.3 dB. Wow and flutter is listed as below measurable limit, which is what you'd expect from a laser reading a disc and not a capstan dragging tape across a head.
The MDS-JE640 is a MiniDisc deck built around the ATRAC codec. The manual names ATRAC and ATRAC 3, with 44.1 kHz sampling and ACIRC error correction. It reads and writes the standard MiniDisc, using a 780 nm semiconductor laser with continuous emission and a maximum output of 44.6 µW measured 200 mm from the objective lens. The disc spins between 400 and 900 rpm under CLV control. None of that is unusual for the format. It is a full-width component, 430 × 95 × 285 mm including projecting parts and controls, and it weighs roughly 3.1 kg, a touch heavier than the JE440, which the manual puts at 3.0 kg. The extra weight comes from hardware the 640 carries and the 440 doesn't.
That hardware is where the JE640 differs. It has a stereo phone jack rated at 28 mW into 32 ohms, and the JE440 does not. It has a setup menu that trims the analog output level anywhere from - 20.2 to 0.0 dB. The level resets to the factory 0.0 dB setting whenever you eject the disc or power the deck down, so an evening spent dialing in a level is lost the moment you swap a disc. It has a sleep timer with 30, 60, 90 and 120 minute settings, defaulting to 60. It has keyboard support, with a menu item to select US or JP keyboard type and another to assign characters. And it has CONTROL A1II, Sony's system bus for chaining separate components. The manual describes it as providing a path for control signals that enable automatic function selection and synchronized recording between an MD deck, CD player, amplifier and cassette deck. The manual also admits that older components won't be compatible with functions added in later revisions of the bus.
European models get a further set of connections the rest of the world didn't: a second digital optical input and a digital coaxial input, the latter a phono jack at 75 ohms impedance rated for 0.5 Vp-p ±20%. Every version has the square optical digital input at 660 nm, analog inputs on phono jacks at 47 kilohms impedance with a 500 mVrms rated input and 125 mVrms minimum, analog outputs rated 2 Vrms into 50 kilohms with a load impedance over 10 kilohms, and a digital optical output at - 18 dBm.
Editing is where MiniDisc decks pulled ahead of tape, and the JE640 has the full set. The single-function edit menu on the 640 is reached by pressing S.F EDIT directly, rather than the multi-step menu the JE440 requires. It gives you track-level recording adjustment in 2 dB increments between - 12 and +12 dB, and fade-in/fade-out recording with times settable from 1 second to 15 seconds in 0.1 second increments. The manual is blunt about the caveats. You can't change the recorded level of a track recorded in LP2 or LP4 stereo mode, repeatedly changing levels degrades sound quality, and the level will not return to its exact original value even if you dial it back. Fade-in and fade-out play affect the analog outputs and the headphone jack but explicitly do not change the signal at the digital output.
The display uses a music calendar grid that shows track numbers, and a symbol appears beside the fifteenth track once a disc exceeds fifteen. Separate indicators cover repeat modes (whole disc, single track, A-B), shuffle, program, and the LP2, LP4 and MONO recording modes. The TOC indicator lights when table-of-contents data hasn't been written and flashes while it's being written.
Audio-Express (October 2001, p.65) reviewed the deck and noted the tradeoff at the heart of the format — that data reduction increases in proportion to recording time, with a corresponding loss of fidelity — while confirming the track erase, partial-track erase and track divide functions. That's the honest framing: the JE640 is a well-built, quiet, flexible machine operating inside a codec whose compromises grow with the length of the recording.
Power consumption is 15 W. The deck was sold in versions for the US and Canada at 120 V/60 Hz, Europe at 220-230 V/50/60 Hz, Australia at 240 V/60 Hz, Hong Kong at 220-240 V/50/60 Hz, and other markets with a selectable 110-120 or 220-240 V supply.
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