Audio Database

Image of Integra A-766mkII/50
Commentary

This pre-main amplifier uses the same circuit configuration as the high-end model of the MKII series except for some power and functions.

In tone amplifiers, various elements, including the NF circuit that controls tone characteristics, change the rise and fall characteristics of middle and low frequencies, which adversely affect sound quality. This part of the MKII series that had been overlooked in the past has been thoroughly clarified by computer simulation and various problems have been solved.
In the tone amplifier, a variable β circuit is inserted in the NF circuit to give tone characteristics, and it has four time constants in the ultra-low frequency range. If this time constant is not carefully selected, a flat amplifier with excellent feedback stability cannot be realized. In the MKII series, a circuit that is advantageous to ensure feedback stability in a sufficiently low frequency range is selected and adopted, and a stable circuit with a large phase margin is realized.
In addition, in order to keep the high-pass cutoff high with a simple circuit while taking into consideration the balance between the high-pass and low-pass, and to ensure sufficient dynamic range even with a simple configuration, we have adopted a unique 2-stage circuit with a differential 1-stage emitter grounding.

In order to improve the signal-to-noise ratio, we have selected a PNP type transistor for the tone amplifier section, which has less 1/f noise due to its structure, and set the impedance level at the best point of the noise characteristic of the transistor.

In order to eliminate adverse effects of power supply voltage fluctuations, a differential circuit is used for the tone circuit, which is less affected by voltage fluctuations. In addition, the voltage is supplied through a ± 2 power supply type low voltage circuit with a voltage fluctuation rate of 1.7%, which prevents intermodulation due to voltage fluctuations in the power amplifier section.

Pure complimentary service with improved transient response characteristics in all stages Technologies developed in the conventional Integra series, such as power amplifiers with all stages connected directly, and operational amplifier type equalizer circuits, have also been introduced.

The wood case was sold separately as an option.

Model Rating
Type Pre-main amplifier
Power Amplifier Unit
Rated Output (1 kHz) 8 Ω : 25W + 25W
4 Ω : 27W + 27W
Dynamic Power (IFF8 Ω) 75W
Total Harmonic Distortion Factor (T. H. D., 1 kHz) 0.1% or Less (at Rated Output)
0.04% or Less (at 10W Output)
0.04% or Less (at 0.5W Output)
Intermodulation Distortion Factor (S. M. P. T. E, 70 hz : 7 khz = 4 : 1) 0.05% or Less (at Rated Output)
Power Band With (IHF-3dB, THD 0.3%) 10 Hz to 60 kHz
Signal-to-noise ratio (IHF A network, input shunt) 110 dB or more
Damping factor (DC ~ 20 kHz) 8 Ω : 60
4 Ω : 30
Load impedance 4 Ω ~ 16 Ω
Gain 23.5dB
Output terminal Speaker : A, B, A + B switching
Headphone jack
Preamplifier Section
Input Sensitivity / Impedance Phono1, 2 : 1.2 mV, 2.4 mV, 4.8mV/50k Ω
Tuner, AUX1, 2, Play : 100mV/50k Ω
Total Harmonic Distortion Factor (1 v, 1 khz) Not more than 0.03%
Intermodulation Distortion Factor (S. M. P. T. E, 70 hz : 7 khz = 4 : 1) 0.05% or Less (1 V)
RIAA deviation (Phono1, 2) 20 Hz to 20 kHz ± 0.5 dB
Phono maximum allowable input
(1kHz/10kHz, THD 0.1% (R. M.S.))
Input sensitivity 4.8 mv : 400mV/1850mV
Input sensitivity 2.4 mv : 200mV/970mV
Input sensitivity : 1.2 mv : 100mV/480mV
S/N (IHF A network, input shunt) Phono1, 2 : 75 dB or more
Tuner, AUX1, 2, Play : 90 dB or higher
Output Voltage / Impedance
Pre Out (at 100k Ω load) Rated output : 1V/2.7k Ω
Maximum output : 4V/2.7k Ω
Rec Out(Phono) Rated output : 100mV/12k Ω
Tone Control (2 db Step Type) Treble : ± 10 dB (10 kHz)
Bass : ± 10 dB (100 Hz)
Turnover frequency Treble:2kHz
Bass:400Hz
Loudness (at volume -30dB) +5dB/70Hz
Filter High-Filter : 5 kHz, 6dB/oct.
Low-Filter : 30 Hz, 6dB/oct.
Muting -20dB
<General>
Semiconductor used Transistor : 33
Diode : 20 pcs
Pwer 100 VAC, 50Hz/60Hz
AC Output Switched : 1 system, 200 VA
Unswitched : 1 line, 200 VA
Power consumption Electrical Appliance and Material Control Law Standard : 75W
Maximum power consumption : 160W
External dimensions Width 440x Height 150x Depth 386 mm
Weight 9.3kg
Sold Separately Wood Case CW-5 (¥ 3,000)