Nakamichi PA-70CE (1988)
The Nakamichi PA-70CE is a stereo power amplifier released in 1988. It's a Custom Edition of the PA-70, and the front panel says so. It was priced at ¥420,000 at launch. The record on this model is almost entirely technical. No period reviews or owner listening impressions have surfaced in the available research. What is documented comes from Japanese spec databases, and it goes deep on design.
The circuit is based on the STASIS method, a design approach associated with Nelson Pass, who reportedly had a hand in the PA-70CE's development. STASIS pairs a pure class A circuit, which keeps the amplifying elements in their most linear state, with a current-mirror bootstrap section (class AB) that supplies current to the speakers. The two drive the speakers in parallel. That gives high stability and drive capability and gets rid of overall negative feedback. There are 36 power transistors (rated 130W each) - 2 in parallel for the STASIS section, 7 in parallel for the bootstrap section. Output terminals are connected directly by gold-plated copper bus bars to equalize impedance. The power supply is substantial: a 700 VA toroidal transformer, 33,000 µF × 4 custom film capacitors, a high-speed diode bridge, and an inrush current limiter.
The chassis is a "skeleton" design. The transformer and capacitors sit on a thick chassis plate running front to back, with a steel angle frame assembled around it. All parts got a thick electrodeposition coating to reduce resonance. The heat sink is a single ultra-large unit, the top cover is 3mm aluminum, and the AC cable, power switch, and inrush limiter are isolated from the audio section. Internal wiring is Nakamichi's oxygen-free copper single-wire cable (3.4mm core), the PCB uses oxygen-free copper foils, and the AC cord is OFC as well. Output terminals come in two gold-plated types, standard binding posts and large brass machined vise-type, and both are bi-wirable. A high-speed multi-sensing protector monitors the transistors in real time, and a ceramic-powder-filled damping fuse is used. A dedicated tester checked each unit at the factory for sound quality against B&W 801 monitor speakers.
Rated output is 225W + 225W into 8Ω (20Hz - 20kHz, 0.05% THD), with frequency response of 20Hz - 20kHz +0/-0.2dB at 1W. Signal-to-noise is rated at 120dB or more (IHF, A-weighted, input shorted, rated output). Maximum output current is 90A per channel, and power consumption reaches up to 900W. The unit measures 435 × 200 × 421mm and weighs approximately 28.5kg.
- Rated output: 225W + 225W (8Ω, 20Hz–20kHz, 0.05% THD)
- Frequency response: 20Hz–20kHz +0/-0.2dB (1W)
- S/N ratio: 120dB or more
- Maximum output current: 90A per channel
- Power consumption: up to 900W
- Dimensions: 435 × 200 × 421mm (W×H×D)
- Weight: approx. 28.5kg
A single 2022 eBay listing shows a used PA-70CE selling for $3,699 with operation confirmed. A Russian owner noted their unit arrived from Japan already serviced, with only a missing rubber ring on an output terminal as a flaw. Beyond that, no market data, common-failure information, or spare-parts availability is documented. No available source states how the PA-70CE relates to Nakamichi's other STASIS-era amplifiers (the PA-5 II, PA-50CE, or the better-known PA-7).
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