Luxman SQ-202 (1970–1973)
Seventy watts of early solid-state power in a 12.5 kg chassis - the Japanese-market flagship Luxman built to show what transistors could do.
Overview
The SQ-202 weighs 12.5 kg and is 480 mm wide. It was the top-of-the-line Luxman pre-main amplifier at its July 1970 release, and the weight tells you that. Under the crackle-paint steel top panel and silver faceplate sit a massive transformer and a fully compartmentalized layout. Luxman's service documentation breaks it down board by board, from the PB 931 equalizer to the PB 937A power supply. According to the service manual, the SQ202 is constituted by equalizer, microphone amplifier, intermediate amplifier, tone control, filter, meter, power source and main amplifier circuits, with almost all of them mounted on separate PCBs.
Luxman rated the main amplifier at 70 watts RMS into 8 ohms with both channels driven. On a single channel it gives 80 watts RMS into 8 ohms and 100 watts RMS into 4 ohms. The company's documentation describes the output section as a DC SEPP full complementary system with a two-stage differential driving circuit and dual power supply. It is not Class A, despite claims that occasionally circulate. It is a push-pull design, and the service manual's parts lists confirm it. Owners and technicians who have lived with the SQ-202 describe it as gorgeous, powerful, and detailed, with a clean, dynamic presentation rather than tube-like color.
The French collector community has long treated the SQ-202 as the tout haut de gamme - the absolute top of the line - for Luxman's early transistor integrateds. One source calls it simply the very top of the range of Luxman in transistor integrated amplifiers. It is also rare. The SQ-202 is not a common sight on the secondhand market, and when one appears it is usually in need of restoration.
Key Features
Independent Phono 1 and Phono 2 Equalizer Boards
Most integrated amplifiers of the era routed two phono inputs through a single equalizer stage and switched between them at the input. Luxman did it differently. The service manual is explicit: on this model independent amplifiers are provided separately for phono 1 and phono 2 in order to evade the various inconveniences that take place at the time of selection - inductance noise, shock noise, and adverse effects on tonal quality caused by shield wire. The equalizer circuit is a three-stage direct-coupled NF type built around the 2SC1000 NPN transistor, with four complete circuits for the right and left channels. Phono 1 presents a fixed 50 kΩ load. Phono 2 offers selectable 30 kΩ, 50 kΩ, or 100 kΩ impedance, which helps if you are running anything other than a standard moving-magnet cartridge. Sensitivity is 2 mV on both inputs, with a permissible input voltage of 180 mV before overload.
DC-Coupled Signal Path with Dual Power Supplies
Luxman's own documentation states that all stages are directly connected by using two power supply circuits and eliminating the coupling capacitors at the output stage. In 1970, DC coupling was still relatively rare in consumer gear. Most designs used capacitors to block DC offset, and those capacitors colored the sound as they aged. The main amplifier section runs an emitter-follower circuit at the first stage to make input sensitivity variable, and the overall configuration is a semi-differential SEPP system using a complementary service amplifier circuit. High-voltage transistors were specified to raise the maximum allowable input voltage to approximately 30 V, which is why the main-in input can accept a 700 mV signal for 50W of output without strain.
Selectable Center-Frequency Tone Controls with Defeat
The tone control circuit uses Luxman's exclusive NF-type design with switchable bending points - 150 Hz, 300 Hz, or 600 Hz on the bass side, and 1.5 kHz, 3 kHz, or 6 kHz on the treble side. The service manual describes the implementation: the variation of tonal quality is made at bass range by VR3 and treble by VR4, with the turn-over and roll-off frequencies selected by switches S12 and S13. When both switches sit at the defeat position, the signals are shut out at the tone control circuit entirely and fed direct to the following stages.
Four-Pole Filter Circuit, 12 dB per Octave
The filter section is NF type with a sharp 12 dB/octave response. The service manual notes that individual amplifiers are arranged for the low-cut 30 Hz and 80 Hz positions and the high-cut 5 kHz and 9 kHz positions - eight amplifiers in total across both channels. Rather than switching CR elements in and out of a single filter, Luxman switched the entire circuit, sending a signal to each circuit only as required. The manual puts the benefit this way: high sound quality is achieved by switching the entire circuit instead of switching the CR element. Like the tone controls, the filters do not function at the flat position. They simply step out of the signal path.
Separable Pre and Main Sections
The preamplifier section and the main amplifier section can be used independently. With Pre-Out at 700 mV into approximately 100 Ω and Tape Out at 110 mV into the same impedance, the unit can run as a standalone preamp feeding a modern power amplifier. The main-in input also accepts 700 mV at about 100 kΩ impedance, so the power section can be driven directly from an outboard preamp, bypassing the Luxman front end entirely. The preamp offers a maximum output voltage of approximately 5 V, frequency response from 20 Hz to 70 kHz within -1 dB, and THD below 0.05% at 1 kHz on the aux inputs.
Three-Position VU Metering
The SQ-202 carries a VU meter with a rear-panel switch that selects among three indication modes. The service manual describes them: indication on PRE OUT level, on full power (0 dB) at the power amplifier section, and on the same under attenuation (-14 dB). With the selector at PRE, the meter reads the preamplifier output, with 0 VU corresponding to 1 V. Switch it to Main 0 dB or Main -14 dB and the meter tracks the power amplifier instead.
Microphone Mixing and Front-Panel Inputs
The microphone head amplifier is independent, built on its own board (PB 933) with four 2SC1000 transistors - two per channel - and it can be mixed with any of the other input signals. The mic level setters are mounted directly to the board alongside the input jacks. The front panel carries tape-out and tape-in terminals for recording and monitoring without reaching around the back. The input selector covers phono 1, phono 2, aux 1, aux 2, and aux 3, plus two tape loops. There is also a stereo/reverse/mono L/mono R/mono L+R mode selector, an input level setter for aux 2, and a three-position impedance selector for phono 2. The control layout, with its wide center row of switches, would resurface later in the 1970s with the L-5 series and again in export-only receivers through 1979-1981.
Protection Circuit and Modular Construction
The protection circuit uses a current-limiting method and operates while performance continues — meaning it does not shut the amplifier down but limits current to protect the output stage. The service manual also documents the modular architecture: amplifier modules are removable and designed to be serviced independently, the phono stage sits on its own board, and the entire layout is compartmentalized. That serviceability was a big deal in 1970, and it remains the reason so many SQ-202s are still running today. Amplifier modules may exist in different revisions — PB-930 versus PB-930A — so matching or upgrading them requires careful attention.
Historical Context
The SQ-202 arrived in July 1970, when Japanese manufacturers were pushing solid-state design hard. Sansui, Yamaha, and Pioneer were all in the thick of it, and Luxman, a smaller, more specialized house, answered with a flagship that prioritized engineering rigor over feature count. The company would later become best known for its vacuum tube amplifiers in the mid-to-late 1970s and 1980s. Luxman units were not all that common in the US market at the time.
Production ran through March 1973. The SQ-202 also spawned a Bic/Lux receiver variant called the 71/4R - essentially a 202 with an AM/FM section grafted on - which is ultra-rare. The model sits at the top of a family that shares design similarities with the SQ-507X, though the SQ-202 is the flagship of that group. As one source puts it, the SQ-202 is part of the first-period Lux design masterpieces - very rare, and very much worth seeking out.
Collectibility & Value
There is no standardized price guide for the SQ-202, and recent listings do not provide clear data. A single unit was listed for sale at the time of research, marked sold or expired, with no price shown. The SQ-202 is not a common sight, and when one appears it is usually in need of restoration. A fully serviced unit could command a premium among vintage Japanese audio enthusiasts, but buyers should expect to invest in the amplifier before they can enjoy it.
The common failures are well documented. Volume and balance control potentiometers fail and are difficult to source today. Hum, blown amplifier channels, and leaking electrolytic capacitors are frequent after fifty years, especially if the unit was left powered on or stored in humid conditions. Those leaking capacitors can damage transistors and resistors over time, so a full recap is often the first step in any restoration. Beyond capacitors, owners should plan on replacing aging tantalum capacitors, updating the main power supply diodes and capacitors, swapping signal path capacitors for polypropylene types, and upgrading phono stage resistors to metal film with modern low-noise transistors. The carbon resistors in the power amp can also be replaced with metal film for improved stability and lower noise. Schematics and service manuals with full-size PCB layouts are available, and the modular design means a faulty amplifier module can be rebuilt without desoldering half the chassis.
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