Nakamichi PA-7II (1989–1993)

The PA-7II is the second-generation version of Nakamichi's big stereo power amplifier, and its story is better documented than most of the company's separates. The first PA-7 was, per forum accounts, essentially a direct copy of a Threshold design, and a lawsuit followed. Nakamichi's revised PA-7II addressed the earlier amp's issues, cleaned up the power supply wiring, and added roughly 25 watts per channel. A service manual for the PA-7II and its siblings survives. It confirms the design is built around Threshold's STASIS topology, used under license.

The manual is the most reliable source for the numbers, and they're better than the spec sheets floating around online. Continuous average power is 225W × 2 into 8Ω, both channels driven, 20Hz - 20kHz at 0.05% THD. Dynamic power is 340W into 8Ω, and rated power bandwidth is 5Hz - 50kHz. Frequency response is quoted as 20Hz - 20kHz +0/−0.2dB at 1W, extending to 7Hz - 150kHz +0/−3dB. Signal-to-noise is better than 120dB (IHF A-weighted). The output stage uses 18 transistors per channel, with 20A continuous / 90A peak current capability. Weight is about 28.5kg. The "Other" version has a rear-panel voltage selector for 110/120/220/240V, and the amp was made in Japan. Production ran from 1989 to 1993, with a list price of $1,635.

Owners tend to be devoted to it. One long-time admirer described finally buying one after nearly 25 years of wanting it. He called it "still one of the best amps I've ever owned" and a clear step up from the Carver that preceded it. He also noted it runs warm rather than hot, and that an overhaul should be considered part of ownership at this age. The known weak point is the thermofuse buried in the potted transformer. A documented failure on a PA-7AII (the closely related variant) involved shorted speaker outputs taking the fuse out and leaving the amp dead until repaired. Spare parts are reportedly hard to find, and the usual advice is to have a used example checked over before buying.

• Power output: 225W × 2 into 8Ω, 20Hz–20kHz, 0.05% THD (per service manual); 325W into 4Ω per owner reports
• Dynamic power: 340W into 8Ω; dynamic headroom 1.7dB
• Frequency response: 20Hz–20kHz +0/−0.2dB (1W); 7Hz–150kHz +0/−3dB
• S/N: better than 120dB (IHF A-weighted)
• Output complement: 18 transistors per channel; 20A continuous / 90A peak
• Weight: approx. 28.5kg (62 lb 13 oz)
• Dimensions: 17-1/8 × 7-7/8 × 16-9/16 in (W×H×D)
• STASIS circuit under license from Threshold Corporation
• List price: $1,635; production 1989–1993; made in Japan

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