Luxman G-120A
Ten bands in a chassis that Luxman's own manual says weighs 5.2 kilograms in metal, 4.9 in wood.
Overview
The G-120A is a stereo ten-band graphic frequency equalizer. Open one up and most of the circuit is discrete transistors, not an off-the-shelf op-amp chip. The parts list confirms it: banks of 2SC1815 and 2SA1015 transistors, a row of 2SC732 TM devices labeled Q601A through Q601J, and a pair of 2SC1626 outputs on their own heat sinks. This was not a budget box with a single IC doing all the work.
Ten center frequencies are spaced at 28 Hz, 55 Hz, 110 Hz, 220 Hz, 440 Hz, 880 Hz, 1.8 kHz, 3.5 kHz, 7 kHz, and 14 kHz. Each has a maximum variable amount of ±12 dB and a Q of roughly 2.3. That is essentially an octave per band across the audible range, so the sliders behave predictably. You can pull down a room mode at 110 Hz without gutting the 55 Hz octave below it. The manual lists a bandwidth figure of better than −80 dB at 1 kHz. That is a channel separation spec, not a bandwidth figure. The manual's table formatting is muddled there, so read that row as separation.
The headline numbers are good for the era. Total harmonic distortion is not more than 0.01% at 1V output across 20 Hz to 20 kHz in the flat position. Intermodulation distortion is no more than 0.01% at the same output with a 60 Hz/7 kHz 4:1 test signal. Frequency response runs 10 Hz to 100,000 Hz within −1.5 dB at flat. Signal-to-noise is better than 110 dB, IHF-A weighted with the input short-circuited, and residual noise is below 0.02 mV. Output voltage is typically 1V, maxing at 5V at flat. Input impedance is a relatively low 65k ohms, reportedly, which matters if you plan to hang this off a tube preamp with a high output impedance.
The front panel has a function switch with normal, bypass, and rec positions, a tape monitor switch, an input attenuator, and an overlevel indicator that lights when the input stage is pushed too hard. The bypass position lets you A/B the equalization against a straight wire without unplugging anything. That is how you find out whether your tuned curve is actually helping.
There are two variants. The metal-cabinet version measures 438 by 270 by 110 mm and weighs 5.2 kg net. The wooden-case version is slightly larger at 465 by 290 by 122 mm and slightly lighter at 4.9 kg net, with gross weights of 6.5 and 6.2 kg respectively. Both share the same front panel, the same shading cloth over the slider area, and the same protective covers on the power and tape monitor knobs. The rear panel differs by market - the J, E, and S versions get one rear panel part number, the U version another. The power transformer is region-specific across four part numbers covering 100V, 120V, 220/240V, and a multi-voltage export version.
Period advertising places the G-120A in Luxman's early-1980s lineup. Luxman marketed it as part of a "DuoBeta" trio alongside the C120 preamp and the M120A power amplifier, which the company billed at 120 watts per channel minimum RMS into both channels driven. The G-120A was the tone-shaping member of that family, the piece you added when you wanted to correct for the room rather than just the recording. Audio (December 1980, p.7) ran the trio together in a DuoBeta feature, positioning the equalizer as the third leg of a system built around the C120 and M120A.
By the mid-1980s the G-120A was still showing up in buyer's guides. HiFI-Stereo (1984, p.127) listed it as a stereo ten-band graphic equalizer with discrete circuitry. Plenty of competitors at the same price had gone integrated. The same guide noted the aluminum anodized case finish on the units it listed, though the G-120A's own manual documents both metal and wood cabinet options. A separate entry in High Fidelity (1981, p.277) covering equalizers in that price class listed range figures of ±12 or ±6 dB per band and output impedance around 100 ohms. Those rows are from a competitor's spec block in the same table and should not be read as G-120A figures.
The case for owning one today is the same as it was then: ten real bands with a bypass switch, discrete gain stages that are still serviceable, and a parts list detailed enough that a competent tech can rebuild the whole signal path. The electrolytics are the usual suspects. The parts list shows 1000 µF 35WV caps at C501 and C502, 100 µF 35WV at C504 and C505, and a scattering of smaller values throughout. None of that is exotic. The mylar and styrol capacitors in the filter sections are the ones you actually care about, and they rarely drift.
The G-120A is not a transparent piece of wire. It's an active equalizer with a real gain stage, and inserting it into a signal chain adds a device's worth of noise and distortion, even in bypass on some units. Owners report that the overlevel indicator earns its keep. It tells you when there is too much input signal before the sliders start clipping, which many equalizers of the period skipped.
Collectors also mention the slider feel. Ten bands means twenty sliders on a panel roughly 17 inches wide, and the spacing is tight but workable. The shading cloth behind the sliders is a wear item. It fades and collects dust, and replacements aren't stocked anywhere. The knobs have protective covers on the power and tape monitor positions, which suggests Luxman expected people to knock into them.
The manual's alignment procedure is simple enough that anyone can verify a unit is working to spec. Feed a 1 kHz sine at 1V RMS into the input, connect an AC voltmeter to the output, and adjust VR101a and VR101b on board PB-1309 for 1V RMS out on each channel. If a G-120A passes that test and the sliders track cleanly, it's doing what it was built to do.
Luxman documented everything, which helps servicing a lot. The manual carries a full replacement parts list with stock numbers for resistors, capacitors, transistors, diodes, variable resistors, switches, and the power transformer by voltage variant. The level controls are 100k ohm dual-gang pots (RV0250), the input attenuator is also 100k dual (RV0251), and the function switch assembly is documented as SS0133 with a remote wire and rotary shaft. That level of documentation is why these units are still repairable forty-odd years on.
Pricing on the used market is modest. These were never flagship pieces and they aren't treated as such now. A working G-120A with clean sliders and a functioning bypass switch is a useful tool. One with scratchy pots and a dead channel is a project.
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