Sansui AU 111 (1965)

A high-end tube integrated amplifier from Sansui's Blackface No. 1 series, released at the transition between vacuum tube and transistor eras

Overview

The Sansui AU-111 is a stereo pre-main amplifier built around vacuum tubes. It was the highest quality model in Sansui's Blackface No. 1 lineup. Released in 1965, it was the last and most refined tube integrated amplifier the company made before it moved to solid-state designs. The preamplifier and main amplifier sections can be used independently. Sansui designed it for high fidelity, with extensive noise suppression and wide frequency response.

Specifications

Year of Production	1965
Product type	stereo pre-main amplifier (tube integrated amplifier)
Rated output Music Power (IHFM)	96W
Effective output	40W + 40W
Total harmonic distortion factor	0.8%
Intermodulation distortion factor (50 Hz to 5.5 kHz)	0.8%
Power Band Width (IHFM)	20 Hz to 20 kHz (at 0.8%)
Frequency characteristic AUX	20 Hz to 50 kHz ± 1 dB
Hum and Noise (IHFM) AUX	-80dB
Hum and Noise (IHFM) Phono	-70dB
Channel separation Phono	45dB
Channel separation AUX	50dB
Residual noise	2 mV (8 Ω)
Load impedance	8 Ω, 16 Ω
Damping factor	15
Input Sensitivity / Impedance Phono1	0.06mV/3.5 Ω (Using A-604)
Input Sensitivity / Impedance Phono2	0.2mV/30 Ω ~ 100 Ω (Using A-603)
Input Sensitivity / Impedance Tape Head	1.8mV/100k Ω
Input Sensitivity / Impedance Tuner, AUX, Tape Monitor	220mV/500k Ω
Recording output	100 times the Phono2 input, 115 times the Tape Head input
Center channel output	1.5V/48k Ω (Effective Output)
Equalizer characteristics Phono	RIAA
Equalizer characteristics Tape Head	NAB (19cm/s, 9.5cm/s)
Preamplifier output	2.1V/710 Ω (Effective Output)
Tone control	Low: Defeat, 250 Hz, 500 Hz; High: Defeat, 5 kHz, 2.5 kHz
Bass (50Hz)	+11.5 dB to -10dB at 250 Hz, +16 dB to -14.5 dB at 500 Hz
Treble (10kHz)	5 kHz: +12.5 dB ~ -11dB, 2.5 kHz: +7.5 dB to -6dB
Loudness control (at Volume -30dB)	50 Hz: +9.5 dB, 10 kHz: +5 dB
High filter	20 kHz, -25dB, fo = 6 kHz
Low filter	20 Hz, -26dB, fo = 125 Hz
Semiconductors used	Vacuum Tubes (12 pcs): 6L6GC : 4, 12AX7 : 5, 12BH7A : 2, 6AQ8 : 1. Transistor: 2SC-402 : 2. Diode (3 pcs): SW-0.5a : 1, SW-0.5d : 2.
Power supply voltage	AC100V/117V/240V, 50Hz/60Hz
Power consumption	280 VA (max)
External dimensions	Width 460 x Height 170 (Excluding Rubber Feet) x Depth 345 mm
Weight	24.5kg
Original price	¥65,000

Design

The output stage uses 6L6GC tubes in an AB1 push-pull fixed bias configuration. Multiple negative feedback circuits keep the frequency response flat across the entire band. The control amplifier is a 4-stage circuit that includes a cathode follower, and the preamp and main amp can be used independently. The tone control has selectable turnover and roll-off frequencies (two low and two high settings), and each can be defeated. Low-output MC cartridges work with optional Sansui input transformers A-603 and A-604. The tape head amplifier uses a new-type silicon transistor (micro-SEP). The first stage of the intermediate amplifier is a cathode follower with high input and low output impedance. The all-NF amplifier design keeps noise down. Other features include CR feedback low/high filters, loudness control, presence control for improved low-frequency articulation, dual center output terminals (full band and 3D system), tape monitor, phase switching, subvolume and a headphone terminal. The output and power transformers are ultra-wideband types with low constant loss and excellent regulation, guaranteed for life.

Context

The AU-111 came out in 1965, at the transition between vacuum tube and transistor technologies. Sansui marketed it as its final and highest-quality tube pre-main amplifier. It stands alongside the AU-70 as one of Sansui's legendary tube integrated amplifiers. During the 1960s, Sansui established itself as a leading hi-fi brand, and its tube amplifiers competed directly with Western designs.

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