Our ultra-advanced new SD/A-490t includes two vacuum tubes whose classic design has remained unchanged for over 50 years. We and many other critical listeners believe that this anachronistic addition to an already excellent CD player design significantly enhances its sound.
The amplifier that doesn't amplify - Between a CD player's D/A converter and external outputs is circuitry called a buffer amplifier which actually doesn't boost the signal strength at all. Instead, the buffer amp is a unity gain device which increases output current, and acts as a sort of electronic shock absorber, isolating the relatively fragile D/A chip set from the nasty outside world of demanding analog components.
Tubes versus Solid State - More than 98% of all CD players use solid state deivces for buffer amplifiers. A handfull of hard-to-find, esoteric designs in the $1200to2500 range employ one or more tubes instead. In ultra-expensive preamplifiers and power amplifiers, tube sound is subjectively described as "mellower", "warmer", "more open and natural" or simply "less harsh than solid state". Objectively, it's safe to say that tubes; - produce even-order distortion versus transistors odd-order distortion, particularly 3rd harmonics which are especially unpleasant to the ear; - act as a pure Class A device when used in a buffer stage (Class A outputs is considered the optimal amplifier configuration); - "Round off" the waveform when they clip, while over-driven solid state devices cut off sharply, causing audible distortion.
The SD/A-490t's output section - Our new CD player uses two 6DJ8 dual triodes placed between the digital-to-analog converter and a motorized volume control. Operated at less than 30% of their maximum capacity, the tubes achieve a highly linear output voltage with very low static and transient distortion while providing very high dynamic headroom. And because they're "loafing" at ⅓ their rated current capability, the SD/A-490t's tubes are designed to last the life of the CD player without replacement or need for adjustment.
An array of features as rich as its sound - We've designed the SD/A-490t to be both useful and easy to use. 21-key front panel or remote programming. Fixed and variable output. Programming grid display. Random "shuffle" play. Variable length fade. Automatic song selection to fit any length of tape. Even index programming for classical CD's. plus our proprietery Soft EQ circuitry which compensates for variables in special (L-R) information and midrange equalization found in many CD's mastered from analog tapes.
Specifications
Decoding: 1-bit linear, two channels
Frequency Response : 8 Hz - 20 kHz (+0,2 dB -1,0 dB nominal)
De-emphasis Error: +0,5 -1,0 dB Nominal
Output Level at 0 dB : 2,5 volts +_0,5V
Harmonic Distortion: 0,25% Nominal
Signal-to-Noise Ratio 104 dB Nominal
Channel Separation(EQ Off / On): 88 dB / 17 ±1,5 dB Nominal
Channel Balance at 1 kHz , 0 dB: ±0,5 dB Nominal
Wow and Flutter: Unmeasurable (quartz crystal accuracy)
Power Requirements: 120 V or 220 V 50/60 Hz
Power Consumption: 30 W
Dimensions (W x H x D): 483 x 96 x 311 mm (19 " x 3,8" x 12,25")
Net Weight: 4,5 kg (9,941 lbs)
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