Accuphase P-260 (1979)
One chassis, two personalities: 130 watts of Class-AB muscle on demand, or 30 watts of pure Class-A — and the switch between them is electronic.
Overview
The Accuphase P-260 is a stereo power amplifier built in Japan by Kensonic Laboratory, Inc. — the company that would later become Accuphase Laboratory, Inc. — and released in April 1979 at ¥200,000. What makes it worth a second look after all these decades is that it declines to pick a side in the Class-A versus Class-AB argument. In normal operation it is rated at 130 watts per channel into 8 ohms. Engage the pure Class-A setting and that figure drops to 30 watts per channel, but crossover distortion goes with it. Owners get both personalities in one chassis, and the switch between them is handled electronically rather than by re-biasing the output stage.
The rest of the package reads like a design brief rather than a marketing sheet. A MOS FET parallel push-pull output stage, fully symmetrical push-pull topology at every amplification stage, and a circuit that pulls the capacitors out of the negative-feedback loop to keep distortion down. The frequency response is quoted at 20 Hz to 20,000 Hz, +0/−0.2 dB at rated output — a tight, flat window that points at transparency rather than romance. Harmonic distortion is listed at 0.005% or less into 8 ohms, damping factor runs 80 across the 20 Hz–20 kHz band, and the signal-to-noise ratio is a striking 120 dB A-weighted at rated input with the input shorted. Those numbers come from a single Accuphase source page, so treat them as the manufacturer's claims rather than independently bench-verified figures — but they are the manufacturer's claims, and they read like the company meant every one of them.
The chassis measures 445 mm wide, 160 mm tall, and 390 mm deep — a wide, shallow, low-profile box in the Accuphase house style, and one that stacks neatly under a matching preamplifier. The P-260 landed during what the source material calls the "Golden Era" of Japanese high-fidelity audio, and it wears that era's priorities on its face: heavy power supply, discrete output devices, front-panel VU meters, and a faceplate that assumes the listener wants to know what the amplifier is doing.
Key Features
Switchable Pure Class-A Operation via the PAT/PEND Control
The headline trick is the ability to run the amplifier in pure Class-A without touching the bias resistors. Accuphase engages Class-A through a pure electronic switch — the PAT/PEND control — so the transition is smooth rather than a hard relay clunk or a manual re-bias procedure. In Class-A the amplifier is rated at 30 watts per channel into 8 ohms; in normal operation it delivers 130 watts per channel into the same load. That gap is the whole point. Thirty Class-A watts will drive efficient speakers beautifully and will run hot doing it; 130 Class-AB watts will handle the rest of the world. A thermal sensor kicks in at 70°C to regulate bias, which matters when you are asking a 1979 amplifier to sit in Class-A for hours. Collectors note that thirty honest Class-A watts is a very different thing from thirty watts of a switching amp on paper — the output stage is genuinely biased into conduction the whole way through the cycle, and it lets an owner hear what the fuss was about without buying a second amplifier.
MOS FET Parallel Push-Pull Output Stage with Hitachi 2SK134 / 2SJ49 Devices
The output stage uses MOS FETs in a parallel push-pull arrangement, built around the original Hitachi 2SK134 and 2SJ49 devices. Those part numbers matter to anyone who has to keep one of these running, because original-stock replacements are the difference between a restoration and a re-design. Every amplification stage in the P-260 uses Accuphase's own symmetrical push-pull design — the company's long-standing approach to keeping the positive and negative halves of the waveform handled by mirror-image circuitry rather than by a single-ended compromise.
Capacitors Removed from the NFB Loop
The circuit takes the capacitors out of the negative-feedback loop specifically to reduce distortion. It is a small sentence in the spec sheet and a large one in practice — capacitors in the feedback path are a common source of phase shift and low-frequency coloration, and pulling them out is one of those choices that separates a serious amplifier from a competent one. Combined with the 0.005% harmonic distortion figure and the 120 dB signal-to-noise ratio, it points to a design chasing a clean, quiet signal path rather than a house sound.
High-Efficiency CI Core Power Supply with Dual Balanced Windings
The power supply runs a high-efficiency CI core with dual balanced windings, feeding two 40,000μF filter capacitors. That is a serious reservoir for an amplifier of this size and class, and it is the part of the design that lets the P-260 deliver its 130-watt rating without sagging on transients. The dual balanced winding arrangement is the sort of thing Accuphase has always done well, and it is the reason these amplifiers tend to feel more substantial than their wattage suggests.
Front-Panel VU Meters and Input Level Attenuator
Front-panel VU meters are part of the package — the aftermarket lamp-kit trade for the P-260 (shared with the P-300X) is proof enough that the meters are there and that owners care about keeping them lit. There is also an attenuator for setting input level, which gives the P-260 a degree of system-matching flexibility that a lot of power amplifiers of the period simply did not offer. It lets the amplifier sit behind a preamp with a hotter-than-usual output, or be trimmed to match a source directly, without adding another gain stage to the chain.
Historical Context
The P-260 was released in April 1979 and came out during what the source material calls the "Golden Era" of Japanese high-fidelity audio. Accuphase lists it among its "Classic Models Reference," the company's own short list of designs it considers foundational. The company behind it was founded in 1973 with the P-300 amplifier and C-200 preamplifier, and it began life as Kensonic Laboratory, Inc. before later becoming Accuphase Laboratory, Inc. The P-260 sits squarely in that early lineage — a 1979 design from a company that was, at that point, barely six years old and already building amplifiers that would end up on its own reference list decades later.
Collectibility & Value
The P-260 originally sold for ¥200,000, and an optional wood cabinet — the A-8 — was sold separately for ¥15,000. Today the amplifier trades in a range that reflects both its Accuphase badge and its age: recent eBay listings have shown examples at $1,350, $1,396, and $1,825, alongside a $20 replacement relay kit for owners doing their own servicing. A forum estimate cited around $1,000 as a possible discounted figure, a shop price of around $1,400 was reported for a P260 in good order, and Russian-market listings have asked 57,000 RUB, 120,000 ₽, and 264,790 ₽ — so the spread is wide and condition-dependent. As Audio (September 1995, p.101) records, Audio Classics listed an excellent-condition P260 at $759 among its for-sale amplifiers that month.
Buyers should go in knowing the common failure points. LED failures on D3 and D4 are a known issue — component D3 is identified as a TLR120 — and dim meter lamps are a recurring complaint on auction listings, with aftermarket VU-meter lamp kits sold for the P-260 and P-300X. DC offset instability, distorted output in one channel, and damage from water or earlier repairs are the other problems to check for. A schematic is available on hifiengine.com for anyone doing their own work. The P-260 is not a plug-and-play collectible; it is a 1979 Class-A-capable amplifier that rewards a buyer who knows how to test one before handing over the money.
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