Hitachi SR 903

Well… I like Hitachi, I think they made great stuff, and this, is one excellent receiver.

When you ear Hitachi you don’t think that this company had created audio stuff that could compete with big names in vintage audio like Sansui, Pioneer, Kenwood or Marantz.

You have to check Hitachi receivers, specially the TOTL twin brothers SR 903/904 to understand why.
This is the 1977 Hitachi SR-903, the 904 was a small cosmetically update to the 903 and addition of VU meters.
VU meters are cool, but I like more the 70s look of the 903 and the aluminum knobs…

They are big, well-built, crispy in details, clean and dynamic, well controlled bass, a sound beast.
All the parts inside of them where manufactured by Hitachi except the filter caps. Massive transformer and an outstanding number of transistors.

This receiver uses the Hitachi Class-G topology, it has a 3 rail which allows additional voltage swings and increase peak power output at certain frequencies, other brands at the time try to use it, but Hitachi know how to do it right and this receiver is one stable beast that sounds great. And that is why there is a “Dyanharmony” badge!
The power output stage of the SR-903 is rated at 75 watts per channel RMS. However, during musical peaks, the high output stage automatically produces 160 watts per channel RMS to prevent clipping and distortion. Nice!

StereoMagazine sayd:
“It can produce a little more than 3 dB above rated power – that is, twice its continuous wattage rating on transient peaks without clipping, rivaling in this case the performance on many a superamp. … performance far exceeds what can be rightfully expected of a conventional 75 watts amplifier. The generous headroom contributes to a sense of ease, clarity and crispness.”


Audio Section
Min. RMS Continuous Power Output (both channel driven):
75 W +75 W (8 Ω, 20-20,000 Hz, THD 0,1%)
95 W + 95W (8 Ω, 1 kHz, THD 0,1%)
105 W + 105 W (4 Ω, 1khz, THD 0,1%)
Music Power (IHF): 160 W + 160 W per channel into 8 ohms
Power bandwidth: 10 Hz – 50 kHz
Frequency Characteristics: 10 Hz – 30 kHz ±1 db
Total Harmonic Distortion:
At rated output : less than 0,1%
At ½ rated output: Less than 0,03%
Intermodulation Distortion:
At rated output : 0,1%
At ½ rated output: 0,03%
Input Sensitivity/Impedance:
Phono : 1,9 mV/47 k Ω
Aux : 150 mV/50 k Ω
Tape 1, 2 : 150 mV/50 k Ω
Adaptor : 150 mV/50 k Ω
DIN : 400 mV/120 k Ω
Output level
Tape Out :
150 mV : phono, Aux at rated input;
200 mV : FM 400 Hz, 30% dev. Input; 1 mV;
150 mV : AM 400 Hz, 30% mod. Input ; 1mV
DIN Out : 40 mV (phono at rated input)
Signal-to-Noise Ratio (IHF, Input shorted, A-network, rated power):
Phono : 75 dB
Aux : 87 dB
Tape : 87 dB
Damping Factor: 45 (1 kHz, 8 Ω)
Equalizer: RIAA ±0,5 dB
Bass Control: ±10 dB at 100 Hz
Midrange Control: ±6 dB at 1 kHz
Treble Control: ±10 dB at 10 kHz
Loudness Control: +9 dB at 100 Hz ; +4 dB at 10 kHz
High Filter: -8 dB at 10 kHz
Low Filter: -8 dB at 50 Hz
Semiconductors: 5 Ics; 1 FET; 57 Transistors; 62 Diodes; 1 Thyristor
FM Section
Frequency Range: 88 – 108 MHz
Usable Sensitivity (IHF): 9,3 dBf (1,6 µV)
Signal-to-Noise Ratio [Mono/Stereo]: 74 dB / 68 dB
Total Harmonic Distortion [Mono/Stereo]:
At 100 Hz : 0,2% / 0,3%
At 1 kHz : 0,15% / 0,25%
At 6 kHz : 0,25% / 0,3%
Frequency Response: 30 Hz – 15 kHz ±1 dB
Image Response Ratio: 85 dB
Spurious Response Ratio: 100 dB
IF Response Ratio: 100 db
Altenate Channel Selectivity: 80 dB
Capture Ratio: 1 dB
AM Suppression: 55 dB
Stereo Separation: 45 dB
Sub-Carrier Suppression: 65 dB
SCA Rejection: 65 dB
Muting Threshold: 14 µV
Antenna Input:
Balanced : 300 ohms
Unbalanced : 75 ohms
AM Section
Frequency Range: 530 – 1,605 kHz
Sensitivity: 300 µV/m (S/N 20 dB); 20 µV (IHF, ext. Antenna)
Image Rejection: 70 dB
IF Rejection: 90 dB
Selectivity (IHF): 40 dB
Signal-to-Noise Ratio: 50 dB
Antenna: Ferrite and separate terminal
Tape Monitor: 1,2
Speaker Switch: A, B, A + B
Speaker terminal: One-touch terminal
Power Supply: 100/120/220/240 V 50/60 Hz
Power Consumption: 615 W at 4 Ω; 430 W at 8 Ω
Dimensions (W x H x D): 490 x 144 x 400 mm
Weight: 13,5 kg (29,8 lbs)

2 thoughts on “Hitachi SR 903”

  1. I own one and yes this receiver has commanding power clean throaty bass clean sound ive got a hitachi made rca dientia power amp with it and wow what an amazing pairing , the pairing put her right up onto as far as im concerned and I may add a Japan made hitachi eq only to clean up the amp a little but amazing surprise to any ear . To me for all makes of its time have no competitor to put up against this powerhouse unit

    1. Hello Brian.
      Thanks for sharing your opinion.
      I ended up selling my Hitachi, but I miss it, so if I get the chance to buy one I will…
      From what I remember it didn’t natively have a preamp output and main input, correct me if I’m wrong.

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