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Luxman L 309 (1973)

A 12.5-kilogram integrated amplifier that taught Luxman's whole line to tilt - and the Linear Equalizer is why.

Overview

Twelve and a half kilograms is a lot of amplifier for 80 watts a side. The Luxman L-309 arrived in September 1973 as a mid-to-high-end integrated, a "pre-main amplifier" in the phrasing of the Japanese catalogs. It sat one rung above the L-308 in the lineup, and it carried the feature that would define Luxman's next several years: the Linear Equalizer.

A conventional tone control boosts or cuts one end of the band. Luxman's Linear Equalizer is a five-step tilt filter that rotates the RIAA playback curve around 1 kHz. Turn it up and you get more bass with less treble. Turn it down and you get the reverse. It is a different tool from a bass knob, and it is the most distinctive thing about this amplifier. The regular tone controls are still there, Luxman's NF-type design with switchable turnover points, but the Linear Equalizer was the new idea.

The circuit is a fully complementary DC power amplifier section with a dual-rail power supply and a three-stage DC equalizer for the phono stage. The drive stage runs in class A, kept completely independent from the class B output stage to hold constant voltage. That was a deliberate topology choice, not an accident of cost. The phono equalizer uses an RC4558 op-amp feeding a push-pull output stage in inverted Darlington configuration, also running class A. Luxman separated the power supply for the preamp, driver, and output stages, with two 15,000 μF capacitors filtering the output stage alone.

Continuous effective output is quoted at 80W + 80W into 8 Ω, both channels driven, 20 Hz - 20 kHz. Other sources list the same amplifier at 75 watts per channel. The figure changes depending on whether the source is Luxman's own literature or the enthusiast databases, and either number is close enough that it doesn't change what the amp does. Total harmonic distortion is 0.03% or less at 8 Ω and 80W. Output bandwidth runs 5 Hz to 40 kHz at -3dB, and the line-level frequency response is quoted at 10 Hz to 50 kHz.

Signal-to-noise is 62 dB or more on phono and 80 dB or more on tuner and aux. Damping factor is 40 into an 8 Ω load. Input sensitivity is 2.5 mV for moving-magnet phono and 100 mV for line. Dimensions are 485 mm wide, 165 mm tall, and 300 mm deep, a wide, low chassis that looks like serious equipment on a shelf. Inside, Luxman fitted 47 transistors, a single IC, 20 diodes, 4 Zener diodes, and 6 varistors.

Key Features

The Linear Equalizer

This is the feature that made the L-309 the L-309. The Linear Equalizer is a five-step tilt filter that rotates the preset RIAA curve up or down around a 1 kHz pivot. One direction gives more bass and less treble, the other gives more treble and less bass. It is not a tone control in the conventional sense. It changes the overall tonal balance of the record playback curve rather than boosting a band. For a shelf of LPs cut with wildly inconsistent house curves, an adjustable tilt was a practical tool, not a gimmick. It was also the start of a Luxman staple that carried forward into later models.

Fully Complementary DC Power Amp with Split Supply

The L-309 uses a fully complementary OCL power amplifier circuit with a split power supply and two-stage differential amplification, directly coupled throughout. The output stage runs class B, preceded by a class A predrive stage with an emitter follower buffer. Luxman kept the class A drive stage completely independent from the class B output stage to achieve constant voltage. That separates the small-signal and high-current halves of the amplifier instead of letting them share a rail.

Three-Stage DC Phono Equalizer

The phono section is a three-stage DC equalizer built around an RC4558 op-amp, with a push-pull output stage in an inverted Darlington configuration operating in class A. It is more involved than the era's typical single-op-amp arrangement. It is also the part of the amplifier most likely to benefit from restoration today, and the RC4558 is the component most commonly swapped out during a rebuild.

LUX System NF Tone Controls

The conventional tone controls on the L-309 are Luxman's NF-type design with selectable turnover frequencies. Bass turnover can be set at 150 Hz, 300 Hz, or 600 Hz. Treble turnover can be set at 1.5 kHz, 3 kHz, or 6 kHz. That gives six combinations of tone shaping before you ever touch the Linear Equalizer, which is a lot of flexibility for a single integrated.

Filters and Low Boost

Luxman fitted a low-cut filter switchable between 20 Hz and 70 Hz at 6 dB per octave, a high-cut filter switchable between 7 kHz and 12 kHz at 6 dB per octave, and a low-boost filter at 100 Hz, 6 dB per octave. The block diagram in the service manual confirms all three, plus a defeat switch with normal and tone-plus-low-boost positions. For vinyl, the 20 Hz low-cut and the low-boost give you a pair of tools for dealing with rumble and thin-sounding pressings.

Inputs, Dubbing, and Monitoring

The rear panel carries two phono inputs, tuner, and two aux inputs, plus microphone jacks with pull-on level pots. The L-308 had tape 1 I/O jacks in that position. The L-309 also added a back-panel pot to attenuate the MAIN-in input level. Dubbing runs 2-to-1, source, and 1-to-2, and monitoring can be set to deck 2/4-channel, source, or deck 1. Mode switching covers left, right, mono L+R, stereo, and stereo-reverse.

Historical Context

The L-309 followed the L-308 and introduced Luxman's Linear Equalizer, which was carried forward into later models. Contemporary coverage in the audio press, such as Audio (October 1975, p.39), placed the L-309 alongside other notable integrated amplifiers of the period. It was released in September 1973 as a mid-to-high-end integrated amplifier, and it was designed to pair with the Luxman T-300U tuner.

The L-309V succeeded it in October 1975 as part of Luxman's 50th-anniversary "V" series. The V model moved the phono 1 impedance selector to the front panel, added a three-position muting switch (0 dB, -10 dB, -20 dB), removed the front tape I/O jacks, and upgraded the speaker terminals. It shares the same transformer, PB642 equalizer filter switch, and PB1024 protection/power board as the L-85V, though its protection circuit differs slightly.

A third variant, the L-309X, appeared around 1978 and replaced the earlier versions. It dropped the front microphone and mix inputs and loop, swapped the regular transformer for a large toroidal, and replaced the volume pot with a six-gang ALPS unit. Luxman's sources describe it as an extra-rare and very brief version. Production end years for the base L-309 are not consistently documented. The page title range of 1973 - 1975 reflects the arrival of the V model, not a confirmed discontinuation date.

Collectibility & Value

The L-309 has a following, but you have to know what you are buying. Recent listings for the L-309V, the later variant, have ranged from $253.50 to $1,426, with the higher prices reflecting restored or fully serviced condition. A base L-309 listed recently at €650. Another unit, described as recently serviced and brought to factory standard, was offered at $750, with the seller noting that the power indicator light had gone out but the amplifier still worked perfectly. That dead pilot light is common enough that it shows up in sale listings.

The failure modes are the ones you would expect from a 1970s Luxman, plus a few specific to this design. The most serious is sudden DC offset on one channel, which trips the protection relay. It usually points to a failing component in the output stage. Blown output transistors can cause extensive collateral damage, so a working unit that has never been serviced is not the bargain it appears to be. The bias sensing transistors are known to detach from the heatsinks because they rely on thermal compound alone to stay put. On the equalizer side, the filter switch can develop up to 20 ohms of contact resistance, and the internal switch contacts are prone to dislodging. On the PB1024 power board, the fuse holders were poorly fitted from the factory, and the germanium diode on that board often fails with age.

Restoration typically involves a full recap, replacing the RC4558 op-amp with a quieter OPA2604, and substituting the output transistors with modern equivalents like the MJ15024 and MJ15025. Cleaning the filter switch is its own job: contact spray, an IPA soak, and lubrication after drying. A service manual is available, ten pages and downloadable, which makes the L-309 easier to work on than some of its contemporaries.

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VINTAGE TECHNOLOGY ARCHIVE / 10-16-2026 / FEEDBACK