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

Onkyo Model 931

Model 931 is an independent power amplifier that is so versatile that it can fit into any system. It was designed so that all distortion is reduced to a minimum. Sone of the factors that assure less distortion are quasi complementary SEPP, direct coupled and differential circuitry. The power amplifier circuitry was analyesd by a computer but this analysis was not restricetd to the audible range alone. Onkyo found that the very low frequencies have a very important bearing on the music even though inaudible. Since these low ffrequencies are not taken into account when ordinary amplifiers are designed they cause very much distortion.  This distortion in the very low frequencies causes IM distortion. This model is rated at 22 watts per channel at 8 ohms. The T.H.D. of model 931 is rated at less than 0,05%. Whether the amplifier is used at full or very low power this distortion rate does not vary. Added stability is gained because a differential amplifier is used.   In stability in an amplifier  will put DC voltage on the loudspeaker terminals and this will lead to distortion.  The differential amplifier also takes care of any distortion that could come from fluctuations in the power supply voltage and temperature.  The OCL  circuitry is an added factor why model 931 has less distortion, a flatter response over the whole frequency range and especially good damping in the lower  frequency range.

Two Step Variable Input Sensitivity
The input sensitivity of model 931 is variable so that it can be matched perfectly to any preamplifier. This makes it so very easy to use model 931 in any 4-channel system.

Integrated Right and Left Channel Attenuator
An integrated attenuator for both channels is installed in model 931. This makes attenuation of both channels very easy. With this added feature incorporated into its design model 931 fits very easily into any 4-channel syetem.

Dynamic Power:  70 W (IHF, 8 ohms);  100 W (IHF, 4 ohms)
RMS Continuous Power (Single Channel Driven):
22 W + 22 W (8 ohms, 1kHz)
27 W + 27 W (4 ohms, 1kHz)
Total Harmonic Distortion:
Rated output 1 kHz : less than 0,1%
0,5 W output : less than 0,05%
10 W output : less than 0,05%
Inter Modulation Distortion (SMPTE 70HZ : 7kHz = 4 : 1):  less than 0,05% at rated output
Frequency Characteristic:  10 Hz - 80 kHz (+0 -1 dB at normal output)
Power Bandwidth:  10 Hz - 100 kHz (IHF -3 dB, THD 0,5%)
Signal-to-Noise Ratio:  better than 100 dB (IHF A network input shunt)
Damping Factor:  60 (DC - 30 kHz)
Load Impedance:  4Ω - 16Ω
Gain:  22 dB ,  28 dB
Rated Input Voltage:  1 V,  0,5 V
Input/Output Characteristics:  in -phase
Output Terminal:  Speaker-1
Power:  AC 220 / 240 V,  50/60 Hz
Power Consumption:  30 W (Electrical Goods Control Standards)
AC Output:  Unswitched 1
Dimensions (W x D x H):  130 x 352 x 135 mm (5,2" x 14,1" x 5,4")
Weight:  3,5 kg (7,7 lb)

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