Pioneer SA 9500 II (1977-1979)

Eighty watts per channel into 8 ohms, a hundred into 4, and a twin-tone control stack that lets you shape the bottom end twice over - Pioneer's flagship integrated from the tail of the '70s.

Overview

The SA 9500 II is an integrated stereo amplifier Pioneer built between 1975 and 1979. The company's own literature calls it the crown jewel of the elite "Series 20" lineup, the flagship integrated of its day. The spec sheet backs that up: 80 watts per channel into 8 ohms and 100 watts per channel into 4, stereo, from a chassis that combined cutting-edge solid-state design with no-compromise construction. Pioneer's period advertising made the distortion claim explicit. Audio (March 1978, p.2) ran copy describing a new parallel push-pull output stage that reduced total harmonic distortion to less than 0.1%, a figure the company framed as well below anything a listener could hear. The same advertisement paired the amplifier with the TX-9500II tuner, so Pioneer clearly meant it as the anchor of a matching flagship system and not a standalone box.

The headline wattage isn't what makes this amplifier interesting today. Plenty of late-'70s integrateds made similar claims. The feature set is the draw: a dual power supply, a DC amplifier design, a non-switching output stage, direct-coupled OCL circuitry, and a phono stage that handles both moving-magnet and moving-coil cartridges. That last item separates the SA 9500 II from most of its contemporaries, which typically left MC capability to outboard step-up transformers or dedicated preamps. Add dual power meters, a full tone control section with loudness contour, and filter switches, and you get an amplifier designed for the enthusiast who wanted everything in one chassis.

The tone control section is more elaborate than the typical bass-and-treble arrangement. The SA 9500 II uses what Pioneer called Twin Tone Controls — two separate control circuits with different turnover frequencies on both the bass and treble sides, each usable independently. The manual describes the incoming signal being amplified by a two-stage differential amplifier, with two C-B feedback NFB-type tone circuits connected in series: a main stage and a secondary "sub" stage at a different turnover frequency. On the treble side the sub turnover is higher than the main; on the bass side it's lower. In practice this gives the user far more granular control over frequency shaping than a single-knob-per-band design, and the disengageable tone switch lets you bypass the whole network for a flat response when checking a cartridge or a room.

Key Features

Dual Power Supply and DC Amplifier Design

The SA 9500 II runs separate power supplies, a choice that shows up in the channel separation and in its ability to deliver current into low-impedance loads. Pioneer rates it at 80 watts per channel into 8 ohms and 100 watts per channel into 4 ohms. That's modest on paper by flagship standards, but the conditions attached to those numbers matter. The amplifier section uses a DC design with direct-coupled OCL (output capacitor-less) circuitry, so there's no coupling capacitor between the amplifier and the speakers. No capacitor in the signal path means no capacitor coloration, and the low-frequency response extends further than a capacitor-coupled design typically manages. The tradeoff is that DC-coupled amplifiers are less forgiving of a fault condition, which is where the protection circuit comes in.

Non-Switching Output Stage

The output stage uses a non-switching topology, and Pioneer's period advertising pointed to the parallel push-pull configuration as the key to keeping distortion below 0.1%. A non-switching design avoids the crossover distortion that plagues conventional Class-AB output stages at low signal levels, at the point where the output devices hand off to each other. According to the company's own copy, THD dropped to a level no listener could detect. The manual's circuit description walks through the topology in detail: a two-stage Darlington connection with the final stage forming two complementary symmetrical parallel circuits, and the output midpoint held at 0V by a balanced plus-and-minus power supply and a 100% DC negative feedback loop. The bias voltage for the power stage comes from a variable resistor and a varistor that compensates for thermal drift. The manual's adjustment procedure calls for setting the idler current to 30mV across specific test points, then rechecking after thirty minutes of warm-up.

Phono Stage with MC/MM Capability

The equalizer amplifier is one of the SA 9500 II's strongest arguments for collectors today. It handles both moving-magnet and moving-coil cartridges. The cartridge load is adjustable across four resistance settings (10k, 25k, 50k, and 100k ohms) and four capacitance settings (100pF, 200pF, 300pF, and 400pF), selected by the CARTRIDGE LOAD control knobs on the front panel. The manual says this lets the user optimize the load for different phono cartridges and modify the cartridge's high-frequency response to taste. The equalizer circuit uses polypropylene film capacitors with ±2% tolerance and metal film resistors with ±1% tolerance. Pioneer specifies RIAA deviation at less than ±0.2 dB from 20 Hz to 20 kHz. The input stage is a differential amplifier using PNP transistors, followed by a bootstrap circuit and a complementary-symmetrical SEPP output stage. The manual claims an overload input level of 300mV RMS at 1 kHz with no more than 0.05% distortion. That's a high figure, and it means the phono stage won't clip on hot recordings.

Twin Tone Controls

The bass and treble sections each have two controls. On the bass side, a 100 Hz control adjusts frequencies below 400 Hz with a range of ±8 dB, and a 50 Hz control adds adjustment for the band below 200 Hz with a range of ±6 dB. The treble side mirrors this: a 10 kHz control adjusts frequencies above 2.5 kHz at ±8 dB, and a 20 kHz control adds adjustment for the band above 5 kHz at ±6 dB. The tone switch disengages the entire network in the upper position, giving a flat frequency response. That's useful for checking phono cartridge and speaker tone quality or evaluating room acoustics. The loudness contour, engaged with the volume control set at the -40 dB position, adds +6 dB at 100 Hz and +3 dB at 10 kHz.

Dual Power Meters, Filters, and Front-Panel Facilities

The front panel carries dual power meters. They rely on small bulbs that often burn out, which is a known maintenance item. The amplifier also has a low filter with a 15 Hz turnover at 6 dB per octave and a high filter at 8 kHz, also 6 dB per octave. The speaker selector offers A, B, and A+B positions, plus an OFF setting for headphone-only listening. A muting switch works with the volume control to give finer adjustment at low levels. The volume control scale is marked in dB of attenuation, with maximum volume assigned an arbitrary 0 dB reference. A headphone jack sits on the front panel, and the power switch controls the rear-panel switched convenience outlets as well as the amplifier itself.

Multi-Voltage Versions

The SA 9500 II was sold in four versions, distinguished by their power requirements. The KU type runs on 120V only and carries UL approval for the U.S. market. The KC type is also 120V only but CSA-approved for Canada. The HG type is switchable between 220V and 240V and carries SEMKO, NEMKO, DEMKO, and EI approvals for Scandinavian markets. The S type is the general export model, switchable across 110V, 120V, 220V, and 240V. The manual is written for the KU type, with separate documentation for the other variants.

Historical Context

The SA 9500 II sits at the end of the 1970s, built between 1975 and 1979, and Pioneer positioned it as the crown jewel of the Series 20 lineup — the flagship integrated amplifier of its range. The company's own language describes it as a bold statement of engineering ambition during the golden age of high-fidelity audio, and as the peak of late-'70s Japanese audio craftsmanship where power, precision, and presence converged in one imposing chassis. That's marketing copy, but the feature set backs up the positioning: the dual power supply, the DC amplifier design, the MC/MM phono stage, and the twin tone controls were not features you'd find on a mid-tier integrated. The period advertising paired it with the TX-9500II tuner as a matched flagship system, and a contemporary dealer listing in *HiFI-Stereo* (November 1978, p.164) placed the SA-9500 II at $302.00 — well above the SA-8500 at $230.00 and the SA-7500 II at $165.00 in the same advertisement, confirming its position at the top of Pioneer's integrated lineup for that year. A second period ad, this one in *Audio* (November 1977, p.2), made the same distortion claim as the March 1978 placement, describing the parallel push-pull output stage and the sub-0.1% THD figure.

Collectibility & Value

The SA 9500 II carries a collectibility rating of 8/10, with market values in the $800 to $1,500 range depending on condition and restoration status. That's a wide spread, and it reflects the gap between a tired unit and one that's been properly serviced. Serviced examples with receipts do appear on the secondary market.

The maintenance picture is typical for a late-'70s solid-state amplifier, but a few items are specific to this model. Aging capacitors in the power supply are the most common failure point and should be replaced proactively. The dual power supply design means more capacitors to replace than in a single-supply amplifier. The potentiometers need thorough cleaning to eliminate channel imbalances or scratchy controls, and the twin tone control arrangement means more pots to clean than a conventional design has. The dual power meters rely on small bulbs that often burn out, and spares should be kept on hand. The thermal protection circuit should be checked, and the relays inspected for pitting or hesitation.

The phono stage is the feature that keeps the SA 9500 II relevant for modern collectors. With MC/MM capability and adjustable cartridge loading on the front panel, it can accommodate a wider range of cartridges than most integrated amplifiers of its era, without an outboard step-up transformer.

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