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 using vacuum tube technology, manufactured by Sansui as the highest quality model in their Blackface No. 1 lineup. Released in 1965, it was positioned as the last and most refined vacuum tube integrated amplifier from the company before the shift toward solid-state designs. The amplifier features a dual configuration allowing independent use of the preamplifier and main amplifier sections, and was designed 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 AU-111 uses 6L6GC tubes in an AB1 push-pull fixed bias configuration for the output stage and incorporates multiple negative feedback circuits to achieve flat frequency response across the entire band. The control amplifier section uses a 4-stage circuit including a cathode follower, and the preamplifier and main amplifier can be used independently. It features a tone control with selectable turnover and roll-off frequencies (two low and two high settings), each defeatable. Input compatibility with low-output MC cartridges is enabled via optional Sansui input transformers A-603 and A-604. The tape head amplifier uses a new-type silicon transistor (micro-SEP), and the first stage of the intermediate amplifier uses a cathode follower with high input and low output impedance. Noise is minimized through an all-NF amplifier design. Additional 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), and accessories such as tape monitor, phase switching, subvolume, and headphone terminal. The unit uses ultra-wideband output and power transformers with low constant loss and excellent regulation, guaranteed for life.
Context
The AU-111 was released in 1965, at the transition between vacuum tube and transistor technologies, and was marketed as the final and highest-quality vacuum tube pre-main amplifier from Sansui. 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, producing tube amplifiers that competed directly with Western designs.
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