Luxman LV-105 (1984–87)
The first Brid amplifier: a vacuum tube in the voltage gain stage and MOSFETs at the output, built to sound warm and drive hard at the same time.
Overview
The LV-105 is a hybrid pre-main amplifier that Luxman built around 1985, developed jointly with Alpine. It was the first product of what the company called the "Bridge series" - an attempt to marry the musical character of a tube stage to the grunt of solid-state output devices. Rated output is 105W + 105W into 6 Ω across 20 Hz to 20 kHz, though period sources also cite 80 watts per channel into 8-ohm loads, with total harmonic distortion quoted at 0.008% or less at 1 kHz into the same load (other sources state no more than 0.3 percent). Those are respectable numbers for a hybrid of the period.
The signal path is unusual in a documented way. A FET handles the first stage, a 3-pole vacuum tube sits in the pre-driver stage where high voltage resistance and linearity matter most, and a MOS FET does the work in the final stage. Luxman states that a voltage-controlled amplifier circuit is used in all stages to prevent the interference distortion that current amplification tends to introduce. The chassis combines solid-state and vacuum tube technologies in a single box. The design brief was signal purity, which is the company's own framing, not a measured verdict.
In practice that means a 10.6 kg amplifier, 438 mm wide and only 148 mm tall, that behaves like a tube preamp feeding a MOSFET power stage. The frequency characteristic is quoted as 1 Hz to 200 kHz at −3 dB or less, which is far wider than any source of the era could use and reflects the wideband philosophy of the AV-oriented Brid line. The rear panel carries a 100 VAC, 50/60 Hz power supply. This is a Japanese domestic-market unit, so buyers outside Japan will need a step-down transformer.
Key Features
FET Input, 3-Pole Tube Pre-Driver, MOSFET Output
Three devices make up the topology. A FET at the input gives the stage high impedance and low noise. The 3-pole tube in the pre-driver provides the voltage swing and the linearity that Luxman wanted in the critical gain stage. The MOS FET output delivers the current. The company's literature frames this as combining the "musical characteristics" of a tube with the "power and characteristics" of an FET. The tube complement is documented as 6CG7A. Two tubes sit at the front of the amplifier, and they are visible, so this is not a hidden-tube design.
Voltage-Controlled Amplification Throughout
Instead of amplifying current and converting it later, the LV-105 uses voltage-controlled amplifier circuits in every stage. Luxman's stated purpose is to eliminate current distortion and the interference distortion that current amplification can cause. Every gain block does the same kind of work, and the signal is never asked to switch modes mid-path.
S.T.A.R. Circuit Topology
The S.T.A.R. circuits are the grounding scheme. Luxman explicitly abandoned the conventional approach of sharing ground and power-supply lines between circuit blocks. Instead, every line is drawn directly from a single reference point to each block and signal path. The result, per the manufacturer, is smoother signal flow and reduced interference between stages. It shows up in the noise floor rather than in the spec sheet, and it is the reason the line-level signal-to-noise ratio is quoted at 110 dB.
Phono Stage for MM and MC
Both moving-magnet and moving-coil cartridges are supported natively. The MM input is specified at 2.5 mV / 47 kΩ with a 90 dB S/N ratio. The MC input is 125 μV / 100 Ω with 70 dB. That MC figure is on the low side for a built-in stage. 70 dB is workable but not silent, and owners running low-output MC cartridges should expect a bit of hiss at high volume. The MM stage is quiet at 90 dB.
AV Inputs and Dubbing
The LV-105 carries three AV input routes and an AV dubbing function that copies AV2 to AV1. Line-level inputs (CD, Tuner, AV/AUX) are specified at 150 mV / 40 kΩ with 110 dB S/N. That makes them the quietest inputs on the amplifier and the ones to use for a CD player. Luxman built this as the center of an audiovisual stack, and the AV routing shows it.
Historical Context
The LV-105 was introduced as the first product of Luxman's "Bridge series," a new concept component line built around the tube/FET hybrid idea. Production ran from roughly 1984 to 1987. Original Japanese domestic price was ¥119,000 around 1985, reported elsewhere as over $1,200 at the time. Alpine and Luxman were collaborating then, and the Brid amplifiers carried both names in some markets.
Advertising from the period leaned hard on the tube-rediscovery angle. Audio (July 1986, p.8) described the LV-105 as delivering 80 watts per channel with dual power supplies and Duo-Beta circuitry, framing the design as an answer to distortion caused by devices that amplify both current and voltage. That is a paraphrase of Luxman's own marketing language, not an independent measurement. The same campaign text ran across multiple titles, including HiFi-Stereo (September 1986, p.43), where the copy described the hybrid circuit as delivering sound "virtually indistinguishable from an original live performance." That is advertising, not a review verdict.
Collectibility & Value
Market prices for the LV-105 currently run from roughly $349 for an untested or as-is example up to $738 for a serviced unit. A serviced European listing has appeared around €600. The spread tracks condition and whether the tubes and output stage have been gone through. Units advertised as "Pro Serviced" or "after full quality preventive maintenance" command the top of the range. This is a 40-year-old hybrid with a tube stage that ages, so the premium makes sense.
Owner reports point to two recurring failure patterns. One is a dead channel that prevents the protection circuit from engaging at all. A diyAudio owner traced an open 430 Ω resistor and expected to replace the output devices as well. The other is a no-click, no-sound condition on power-up where the tubes still light, which points to a protection-relay or supply problem rather than a tube failure. Neither is unusual for the era, but both argue for buying a serviced example or budgeting for a technician. Restoration documentation exists covering the power supplies and replacement of missing parts. The 6CG7A tubes are the consumable to watch. The MOSFET output stage is tough but not indestructible, and a shorted output can take the protection circuit with it.
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