Luxman D-107u (1990–1993+)
The Luxman D-107u is a CD player with a vacuum tube output stage. Thevintageknob.org called it a "banal player with a twist," the twist being the two 6CG7 tubes glowing through the front panel. It was sold in Japan as an Alpine/Luxman product at ¥129,000 around 1990. It's best understood as a super-tweaked version of Luxman's bestselling D-105u. The D-107u came late in that series and never quite cohered on its own. The tube-and-solid-state idea it explored would flourish later in Luxman's designs, just not here.
The analog section is the reason to care. Luxman removed the conventional analog low-pass filter entirely and ran the signal through a newly developed output line transformer instead, relying on the transformer's natural attenuation to do the filtering. The signal path goes from D/A conversion straight into a pair of 6CG7 bi-triodes wired as cathode followers, then out through the transformer. Luxman's own literature claimed this "succeeded in completely removing the analog filter, which is harmful to sound quality," and that transformer coupling gave stable transmission even into low impedance loads. A relay-contact muting circuit guards against start-up pulses. The tube heaters get a preheating switch, and there's a display adjustment function for the FL tube's brightness.
On the digital side, the D-107u has no digital output at all. Luxman dropped it to keep the analog path pure, even though the earlier D-105u had one. The conversion scheme is where sources disagree. The Japanese spec sheet (audio-database.com) lists 16-bit linear quantization at 44.1 kHz. Thevintageknob.org says "18bit / 8fs at any rate," and guesses the DACs are two Burr-Brown PCM-series devices - a guess its own author flags as belief rather than confirmed fact. A diyAudio post names an AD1860 chip instead. No manufacturer document settles it, so the converter identity is unresolved. The pickup is confirmed: a Sony KSS-152A, a part that is now essentially unavailable.
Measured performance is respectable without being spectacular: frequency response of 20 Hz to 20 kHz ±1 dB, dynamic range 89 dB, signal-to-noise ratio 105 dB, channel separation 86 dB, and harmonic distortion of 0.09% at 1 kHz. Output voltage is 2.0 V, and the player offers two systems of output - fixed and variable, the variable side run by a motorized (electric) volume. Fade-out time is settable up to 99 minutes in one-minute increments, which pairs with the editing and time-fade functions for tape recording. Terminals are gold-plated. The unit draws 28 W and weighs 10.3 kg, measuring 470 × 147 × 342 mm. Some markets got wooden side panels.
The build is where the D-107u takes its hits. Thevintageknob.org described the internals as "obviously on the low end," with dispersed cabling and a lot of plastic, and judged it "sound-wise a fair player but no more." The build quality kept it out of the league it was meant for. Luxman, in that source's view, could have used a well-selling series to build a genuine flagship and didn't. On the plus side, the same source singles out the copper foils laid over the DACs, ICs, capacitors, power transformers, and output transformers as a real virtue. The transport uses a center-mounted, low-center-of-gravity layout with the optical pickup base isolated from the assembly base by a rubber damper and coil spring to block vibration.
On service, the tray loading belt is a known wear item, and belts are still listed for it. The KSS-152A pickup is the long-term headache. A 104-page English service manual exists. No period magazine reviews of the D-107u surfaced in our research, so the reception record rests on enthusiast documentation rather than the contemporary press.
- Type: CD player with vacuum tube output stage
- Production years: 1990 – 1993+
- Original price: ¥129,000 (Japan)
- Tubes: two 6CG7 (bi-triode cathode follower)
- Pickup: Sony KSS-152A (essentially unavailable)
- No digital output
- Frequency response: 20 Hz – 20 kHz ±1 dB
- Dynamic range: 89 dB; S/N: 105 dB; separation: 86 dB
- THD: 0.09% (1 kHz); output: 2.0 V
- Outputs: fixed and variable (motorized volume)
- Power consumption: 28 W
- Dimensions: 470 × 147 × 342 mm (W×H×D)
- Weight: 10.3 kg
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