What is stereo?




There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.




H.H. Scott '59





Hitachi SR 2004

 Hitachi SR 2004 with its exclusive Class G amplifier delivers 200 watts per channel RMS into 8 ohms with only 0,08% THD. But during demanding musical peaks, that unique amplifier does an amazing thing. It actually doubles its power to 400 watts per channel RMS to prevent any possibility of clipping or distortion. There is no known speaker system or musical recording that the SR 2004 cannot handle effortlessly and magnificently.
 Its host of advanced features include FM auto-lock, FM muting, phase lock loop circuitry, power protection circuit,mic mixing, hi/low filters, dual power meters, detent control, 3 pairs of speaker connections, switches and indicator lights.
For those who want the power and performance of the finest separate components in a compact receiver there is one incomparable answer.  The Hitachi SR 2004
 Features Tuner Section
Dual Gate MOS FET for High Quality FM Tuner
Auto-Lock Circuit
IF BAN D Selector Switch for Flexible Selectivity and SAW FI LTER for Low Distortion
High-Selectivity and Low-Distortion IF Amplifier using IC's and 3 Ceramic Filters
Quadrature Detection
Phase-Locked Loop IC for FM/MPX Circuit
Reed Relays for Cutting out Detuning Noise
MPX NOISE FILTER
FM MULTIPATH Switch with Meter for Best FM Reception
3-gang Variable Capacitor for High Selectivity AM Reception
Ceramic Filter, ICs in AM Tuner
Two Large Easy-to-Read Meters and a Large-sized Flywheel Tuning Knob
 Audio Section Features
Newly Developed High-Efficiency High-Power Audio Amplifier (Series E ..... Class G or Dynaharmony Amplifier)
Twin Power Meters (L and R channels)
Midrange Tone Control
Turnover and Tone Defeat Switches
Calibrated Attenuator (Volume Control)
Audio Muting Switch
Mic Mixing
Tape Dubbing
Low Filter and High Filter
Three Speaker Systems Connection
Electronic Protection Circuit
Adaptor Switch

 DESCRIPTION OF THE NEW CIRCUIT

SAW filter
FM-IF section of this model is so designed that 2 types of the frequency band characteristics (WIDE, NARROW) can be selected.
Namely, when the IF band switch is set to WIDE, the SAW fIlter and 4-pole linear phase filter are used to suppress distortion to a minimum to improve the group delay characteristics. When the IF band switch is set to NARROW, 2 ceramic filters are used in addition to the above SAW filter and the 4-pole linear phase filter to improve selectivity characteristics. In addition, amplification is performed by IF Amp to compensate for losses caused by insertion of the two ceramic fIlters.  Accordingly, positioning at NARROW is convenient when there is interference from a station close by when receiving a long distant station.

Dynaharmony (Class G Amplifier) output circuit
The level of the music source changes momentarily, the percentage of high level (over 1/2 of peak value) is very small, it is only less than 2% of the total music signals.
Large output amplifiers have been used conventionally to playback at high levels without distortion; however, in this case, high voltage is impressed to the output transistor, so the power consumption is large.
Studies have been made, how to obtain high output powers without the increase of the output transistors' consumption in order to improve the efficiency. Thus, the new dynaharmony output circuit (Class G Amplifier) was developed.

Current mirror circuit
This set contains a current mirror circuit which drives the output stage in push-pull operation to keep distortion low.

Constant current circuit
This constant current circuit stabilizes the bias of the main amplifier circuit.

Idle current compensation circuit against power supply voltage fluctuations

Protection circuits
(1) Muting circuit
(2) ASO (Area of Safety Operation) detection circuit (output transistor protection)
(3) DC voltage detection circuit (speaker protection)
Specifications
FM Section
Frequency Range:  88 - 108 MHZ
Usable Sensitivity [Mono/Stereo]:  8,7 dBf (1,5µV) / 24 dBf (8,9µV)
50 dB Quieting Sensitivity [Mono/Stereo]:  12,5 dBf (2,3 µV) / 36 dBf (34,5 µV)
Signal-to-Noise Ratio (at 65 dBf)[Mono/Stereo]:  75 dB / 70 dB
Harmonic Distortion (at 65 dBf)
Narrow [Mono/Stereo]:
100 Hz :  0,15% / 0,25%
1 kHz :  0,1% / 0,2%
6 kHz :  0,25% / 0,3%
Wide [Mono/Stereo]:
100 Hz :  0,15% / 0,25%
1 kHz :  0,07% / 0,1%
6 kHz :  0,2% / 0,3%
Frequency Response:  30 Hz - 15 kHz  +0,5 -1,0 dB
Image Response Ratio:  115 dB
Spurious Response Ratio:  120 dB
IF Response ratio:  115 dB
Alternate Channel Selectivity [Narrow/Wide]:  85 dB / 45 dB
Capture ratio:  1 dB
AM Suppression:  60 dB
Stereo Separation:  50 dB (1 kHz)
Sub Carrier Suppression:  70 dB
SCA Rejection:  70 dB
Muting Threshold:  28 dBf (14 µV)
Antenna Input:  300 Ω balanced, 75 Ω unbalanced
AM Section
Frequency Range:  530 - 1605 kHz
Sensitivity:  370 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
Audio Section
Output RMS Power (both channel driven):  200 watts per channel, min. RMS at 8 Ω from 20 -20,000 Hz, with no more than 0,08% THD
Music Power (IHF):
230 W + 230 W per channel at 8 Ω, 1 kHz, THD 0,08%
230 W +230 W per channel at 4 Ω, 1 kHz, THD 0,1%
400 W + 400 W per channel at 8 ohms
Power Bandwidth:  10 Hz - 40,000 Hz
Frequency Characteristics:
Phono : 30 Hz - 15 kHz  ±0,2 dB
AUX :  10 Hz - 40 kHz  ±1,5 dB
Harmonic Distortion
Less than 0,08% at rated output
Less than 0,03% at ½ rated output
Intermodulation Distortion
0,08% at rated output
0,03% at ½ rated output
Input Sensitivity/Impedance (at 200 W output, 1 kHz):
Phono 1, 2 :  2,5 mV /47 k Ω
Aux :  150 mV / 50 k Ω
Tape 1, 2 :  150 mV / 35 k Ω
Adaptor :  150 mV / 35 k Ω
DIN :  450 mV/ 95 k Ω
MIC :  3 mV / 50 k Ω
Max. Input Level (Phono):  500 mV
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: 5 mV/m)
Output level DIN Out:  40 mV (Phono at rated  input)
Signal-to-Noise Ratio (IHF, Input shorted, A-network, rated power):
Phono 1, 2 :  75 dB
Aux : 90 dB
Tape 1, 2 :  90 dB
Damping Factor:  75 (1 kHz, 8 Ω)
Equalizer:  RIAA ±0,2 dB
Bass Control
±10 dB at 50 Hz turnover frequency 150 Hz
±10 dB at 100 Hz turnover frequency 300 Hz
Midrange Control
±6 dB at 1 kHz
Treble Control
±10 dB at 10 kHz turnover frequency 3 kHz
±10 dB at 20 kHz turnover frequency 6 kHz
Loudness Control (Volume control set at -33 dB position):  +9 dB (100 Hz);  =4 dB (10 kHz)
High Filter:  -10 dB at 10 kHz  (12 dB/oct)
Low Filter:  -10 dB at 50 Hz  (12 dB/oct)
Audio Muting Effect:  -20 dB;  0 dB;  -40 dB
Tape Monitor:  1,2
Speaker Switch:  A, B, C, A+B, B+C, C+A, OFF
Tuning Meter:  2
Power Meter:  2
AC Outlet:  3 (one switched 50 W &2 unswitched total 150 W)
Speaker Terminal:  One touch terminal
FM Muting / Auto Lock:  provided
MPX Noise Filter:  provided
IF Band Filter:  Narroe and Wide
Multipath Filter:  provided
Pre/Main Amplifier:  separable
Adaptor Switch:  provided
Power Supply:  AC 120 - 220 V 50/60 Hz
Power Consumption:  850 W
Dimensions (W x H x D):  580 x 186 x 447 mm (22 ¾" x 7 ½" x 17 ½")

Weight:  25,5 kg (56,2 lbs)

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