Nakamichi SR-2 stereo receiver
The Audiophile receiver :
The Nakamichi SR-2 belongs to the SR and TA models that redefined the word receiver. It offers the same convenience and economy, but each stage is designed like audiophile components - each individually optimized, each individually powered, each isolated for minimum interference. And what a receiver : STASIS power amplification for uniform impedance, inherent stability and tremendous current capability, a moving magnet phono preamp with precise equalization, tone defeat and more : like defeatable conventional tone controls, a 10 preset PLL quartz-lock FM / AM tuner with manual and auto seek tuning
Multi-stage Power Supply :
The SR-2's exceptional performance is due in part to its power supply. Unlike ordinary receivers, the SR-2's transformer has separate windings, and rectifiers for each major section : power amplifier, preamplifier, tuner and display. The tuner is even buffered from other inputs to prevent interference. This unusually exotic power supply permits each section to operate independently of the others - the major advantage of separate components
STASIS amplification :
Audiophiles who hear the SR-2 are amazed at its effortlessly transparent sound. Music has more detail, more impact, more realism - especially played through difficult high-end speakers. The reason is Nakamichi's STASIS amplifiers - a radically different and superior design in which two amplifiers drive the speakers : a high quality low power and a current mirror bootstrap to supply the muscle. The low-power amplifier has lower output impedance than the bootstrap and so establishes the output voltage. Thus it determines the sound quality, but supplies only enough power to correct distortion in the current amplifier. Since a low power amplifier can be designed for virtually perfect performance, global feedback isn't needed as in ordinary amplifiers.
Removing overall feedback ensures uniform output impedance and inherent stability, and, since the amplifier is stable, there is no need to isolate it from the speaker with a coil as is the usual method. This permits the amplifier to control the speaker more precisely and realize its full potential. The current bootstrap can provide tremendous peak current reserves up to 25 amps for low impedance loads
An Audiophile preamp :
Special care was lavished on the phono preamp. The input circuit is a direct coupled discrete design using ultra high gm FETs in a balanced differential configuration. These drive a differential gain stage with RIAA equalization obtained via a direct-coupled precision feedback network. The preamp accommodates MM cartridges only. Thanks to a simulated inductor [gyrator] design, it has maximum rejection in the warp region, minimum loss in bass response and is free of noise pickup
Copper-styrene capacitors and metal film resistors are used in the signal path ensure minimum noise and distortion
An exceptional tuner :
The SR-2's Quartz-PLL-synthesized FM tuner is far from ordinary. Of course the quartz-locked design ensures accurate tuning and eliminates drift, but typical tuners of this type have high residual noise due to reference-frequency jitter. The SR-2 tuner uses a reference frequency twice that of ordinary tuners to improve signal to noise S/N ratio. A dual gate MOSFET front end with high-Q twin varicap diodes provides selectivity equivalent to a four-gang capacitor while a special auto-seek circuit that detects both signal and noise level prevents false stops between or near strong stations
Specifications :
-:®:- Power : 30W RMS at rated THD distortion 0.1%
-:®:- Dynamic power : 45W at 8ohms, 55W at 4ohms
-:®:- Peak output current : 14A per channel
-:®:- 1986 to 1987 vintage
-:®:- Frequency response : 20Hz - 22kHz [+0dB / -0.5dB], 5Hz to 75KHz [+0dB / -3dB]
-:®:- Signal to noise : > 105dB at rated power, Phono signal / noise : 74dB A-weighted
-:®:- tuner FM : mono 14.7dBf [3μV] for 50dB quieting, stereo 37.5dBf [41.1μV]
-:®:- Headphone output : 70mW
-:®:- Dimensions [W x D x H]: 430 x 370 x 100mm
-:®:- Weight : 7.5kg
Display is fully functional, but dim, except for rarely used LEDs
Remote control capable, but no remote with this unit
Tuner does not auto tune correctly, but does function OK,
Just a limited range of tuning frequencies and difficulty tuning [not economic to repair] - we are likely to include a free tuner with this 2nd SR-2
SOLD May 2012 now on trademe to Auckland
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