Toshiba SB-404 (+ Toshiba HR-40X Stereo Phones) Four Channel PRE/MAIN Stereo Amplifier With Matrix Decoder, 1973-1974​, made in Japan

4-channel Integrated Amplifier which carries a four-channel decoder.

SB-404 in is equipped with a QM system decoder unit (part of the catalog had been described as RM system in place of the QM system)
In addition, SB-404S is equipped with SQ decoder as a top model.

It is equipped with a separate pre-main circuit, it can be used as a 4-channel system as it is a discrete method When you connect a 4-channel deck. It can also correspond to the CD-4 system by connecting di modulator a (SY-504).

Pre-main circuit has become a four-system independent configuration.
The transistor in the circuit I am using the Toshiba ultra-low-noise transistor 2SC1000. It has its own due to the PCT process (Perfect Crystal device of Technology), as compared to the conventional low-noise type excellent that one-third in 1 / 2,10kHz at 100Hz characteristics.
In SB-404S uses the 27 pieces of 2SC1000 in all circuit total.

It has a built-in equalizer circuit of condenser cartridge only.
This you can use the Toshiba record player SR-80C and electret type condenser cartridge C-401S series.

The power amplifier circuit I has adopted the whole page hardwired-connection OCL type of IC power pack.
It is to prevent the deterioration of the characteristics due to the coupling capacitor by all each stage direct connection type, and has improved the frequency characteristics and distortion characteristics.

When 2-channel playback is enabled the BTL connection, you can output up by the use of four of the power amplifier.

Усилитель построен на базе 4 x Toshiba Power Pack TH9015S 

Specifications hifiengine | audio-heritage

Effective output (distortion 0.4%)

  • 26W + 26W (8Ω, BTL)
  • 15W × 4 (8Ω)

Music power (IHF, distortion 0.8%)

  • 30W + 30W (8Ω, BTL)
  • 17W × 4 (8Ω)

Total harmonic distortion rate of 0.4% (8Ω, at the rated output)
Intermodulation distortion rate 0.8% (8Ω, at the rated output)
Frequency characteristic 10Hz ~ 55kHz +0 -3dB
Input sensitivity / impedance Main in: 0.5V / 37kΩ
Residual noise 0.5mV (8Ω)
Damping factor 20 (8Ω)
Speaker impedance 4Ω ~ 16Ω (BTL during 8Ω ~ 16Ω)

Preamplifier section:

Input sensitivity / impedance

  • Phono1 MAG: 2.5mV / 47kΩ
  • Phono1 CC: 30mV / 70kΩ
  • Phono2: 2.5mV / 47kΩ
  • Tuner: 150mV / 47kΩ
  • Aux1 (4ch), Aux2 (4ch): 150mV / 47kΩ
  • 4ch Tape: 500mV / 47kΩ

Output level

  • Tape rec: 150mV
  • Din: 30mV
  • Pre out: 0.5V (maximum 4.2V)

Frequency characteristic 5Hz ~ 100kHz +0 -3dB
Total harmonic distortion rate of 0.04% (at rated output)
The maximum input voltage (1kHz)

  • Phono MAG: 100mV
  • Phono CC: 1.2V
  • Tone Control Bass: ± 10dB (100Hz)
  • Treble: ± 10dB (10kHz)
  • Equalizer deviation ± 0.5dB (to the RIAA)
  • SN ratio Phono: 65dB (2.5mV)
  • CC: 70dB (30mV)
  • Aux: 80dB (150mV)

Use semiconductor IC: 5 pieces
Transistor: 27 pieces
Diode: 10 pieces
Power AC100V / 120V / 220V / 240V, 50Hz / 60Hz
Power consumption 60W (maximum) / 16W (when there is no signal)
Dimensions Width 400 × height 115 × depth 280mm
Weight 7.5kg