Nakamichi PA-70CE

Commentary

A stereo power amplifier introduced as a custom edition of the PA-70.

The circuit configuration is based on the STASIS method.
The STASIS system consists of a STASIS circuit (pure class A operation) that maintains the steady state (STASIS) state so that the amplifying element always operates in the most linear state, and a current mirror bootstrap section (class AB operation) that only supplies current to the speakers. These circuits drive the speakers in parallel, achieving high stability and excellent drive capability while eliminating overall NFB.

A total of 36 Pc130W class power transistors (STASIS section : 2 parallel, current mirror bootstrap section : 7 parallel) are used to realize high current supply capability.
The output terminals of all power transistors are directly connected by gold-plated copper bus bars to equalize the impedance between each transistor and the speaker terminal.

The power supply unit has a large capacity that can be easily extracted with a rated output of more than 500W/ch under normal design. By using the power supply unit half-way, the current supply capability is improved and the drive power of the speaker is increased.
The power transformer uses a special toroidal power transformer exclusively for the 700 va Custom Edition with significantly improved regulation characteristics in actual operation. The electrolytic capacitor is equipped with 33,000 μ Fx4 special film capacitor exclusively for the Custom Edition with original tuning.
It is also equipped with a high-speed diode bridge and inrush current limiter that boast excellent response.

The chassis structure adopts a system called skeleton chassis.
In this system, the transformer and condenser are mounted on a thick chassis that passes through the front and back, and a solid frame is assembled with steel angles around it.

Resonance is reduced by applying a thick electrodeposition coating to all steel parts that make up the chassis.
The heat sink uses a fully integrated ultra-large heat sink. The seamless structure ensures uniform temperature conditions between power transistors and increases the rigidity of the housing.
In addition, a 3 mm thick aluminum top cover is used for the top cover.

The AC cable, power switch and inrush current limiter are isolated from the audio section to eliminate any influence on sound quality.

There are two types of output terminals : the normal binding post type and the brass machined large vise type. Both terminals are gold-plated and can be connected by bi-wiring.

Gold plated input terminal is used for the input terminal.

Nakamichi's original oxygen-free copper single-wire cable (core wire diameter 3.4 mm) is used for speaker and power supply wiring.

Printed circuit board with oxygen-free copper foils is used.

Uses a oxygen-free copper AC power cord.

It is equipped with a high-speed multi-sensing protector that draws out the power transistor capability by real-time multi-point observation.

Uses a damping type power fuse filled with ceramic powder.

The Custom Edition is stamped on the front panel.

At the time of shipment from the factory, each unit was checked for sound quality by a B & W 801 monitor speaker and a dedicated tester.

Model Rating

Type	Stereo power amplifier
Rated output	225W + 225W (8 Ω, double-channel drive, 20 hz to 20 khz, THD0.05%)
Frequency characteristic	20 Hz to 20 kHz + 0 -0.2 dB (1W, new IHF)
Signal-to-noise ratio	120 dB or More (IHF, A-WTD, Input Short Circuit, Rated Output)
Total harmonic distortion factor	0.05% (Rated Output, 20 Hz to 20 kHz)
Maximum output current	90A (per channel)
Power consumption	Up to 900W
External dimensions	Width 435x Height 200x Depth 421 mm
Weight	Approx. 28.5 kg