ONKYO Integra T-410DG
¥ 88,000 (around 1978)
Commentary
Digital FM stereo tuner using quartz synthesizer system.
It employs a quartz digital synthesizer system, and the local frequency is synthesized electronically by PLL (Phase Locked Loop).
The frequency is digitally determined at 100 kHz intervals, and the reference frequency of the PLL is derived from the crystal oscillator. This eliminates the cause of tuning deviation and accompanying sound quality degradation.
Built-in 6-station preset digital memory allows you to store up to 6 stations of the desired broadcasting station.
Equipped with an auto-scan function, it can scan automatically and easily find a frequency with a station above a certain level.
You can also select the channel manually, in which the frequency changes by 0.1 MHz (100 kHz) for each push.
It has a built-in clock function that keeps ticking time regardless of whether the power switch is ON or OFF. When the power switch is OFF, the frequency display is switched to the time display. When the power switch is ON, the FM reception function and clock function operate in parallel.
It is equipped with 50% modulation, 440 hz air check and calibrator for setting the recording level of the tape deck, dedicated outputs for recording directly to the tape deck, and multipath outputs for good antenna setting.
The multi-path output terminal is capable of detecting up to 80 dB strong input in a linear manner, and can be used in combination with an oscilloscope to determine antenna settings with less distortion.
Even when there is no oscilloscope, by connecting the amplifier to the multi-path V terminal, only the distortion component can be checked directly by ear.
The front end uses a 3-MOS-FET and a 6-row varactor diode, and employs a two stage RF amplification and double-double-single-tuning circuit configuration to achieve excellent interference rejection performance.
We also thoroughly reduce reception interference (intermodulation interference) caused by two stations in close proximity.
The wide IF uses a MOS-FET with a low noise figure and a wide dynamic range instead of conventional bipolar transistors and ICs. The second gate is also equipped with an AGC to ensure a linear response to strong input.
It employs an IF with 2-stage bandwidth switching that realizes the best sound quality according to differences in radio wave conditions. In the wide mode, a new 4-element linear face filter with the center of the flat band at 10.7 MHz is adopted by the county delay direct view device. By selecting and managing the strict special quality, it is possible to add an accurate reverse special phase equalization filter that compensates for slight undulations.
In the narrow mode, a 6-element linear-phase filter is added to the previous stage of the above filter to sharply cut interference waves from strong adjacent stations.
The 19 khz pilot signal included in FM broadcasting is necessary for stereo separation, but after L and R separation, it was removed with a low-pass filter with a cutoff of 15 khz to prevent mixing into the audio signal. This filter had a negative effect on the high-frequency audio signal. However, in the T-410DG, a pilot canceler is incorporated in the MPX and PLLIC. By sufficiently extending the cutoff frequency of the low-pass filter, the frequency characteristics are expanded to the high-frequency range of 18 khz. In addition, sufficient NFB is applied to the amplifier inside the IC to reduce the generation of harmonic distortion.
When the 19 kHz pilot signal required for L / R separation at MPX is modulated by an audio signal, not only a beat occurs in the high range of the L / respiratory sound audio signal that is finally separated, but also distortion increases in the middle range.
Integra clarified that this is the main cause of distortion in MPX and developed a beat canceler. We succeeded in extracting a pure pilot signal by cutting off all signals except 19 kHz. As a result, we achieved significant results in reducing mid-range distortion and high-range beat, and achieved excellent low distortion over a wide range.
In FM broadcasting, the modulation wave deepens as the amplitude of music increases. In music programs with a wide dynamic range, the modulation wave usually reaches 100 to 150%, with a peak value of 200%. Therefore, even if a tuner receiving this signal shows good quality at 100% modulation, if the sound quality deteriorates rapidly beyond that, it is meaningless to use Hi-Fi.
To solve this problem, the T-410DG employs an IF section, a wide-band ratio detector, a low-distortion MPX section, and a ± 2 power audio amplifier with a large dynamic margin to achieve low distortion even at 200% modulation.
Model Rating
Type | Digital Synthesizer FM stereo tuner | ||||||||
FM Tuner Section | |||||||||
Receiving frequency | 76 MHz to 90 MHz | ||||||||
Practical sensitivity | 1.8 μ V (IHF, 300 Ω) 10.3 dBf (new IHF) |
||||||||
S/N50dB sensitivity | 3.0 μ V (IHF) 14.8 dBf (new IHF) |
||||||||
Image interference ratio | 120dB(83MHz) | ||||||||
IF interference ratio | 110dB(83MHz) | ||||||||
Signal-to-noise ratio | mono:83dB stereo:77dB |
||||||||
Spurious interference ratio | 110dB | ||||||||
2-signal selectivity (± 400 kHz detuning) | 50dB(wide) 85dB(narrow) |
||||||||
AM suppression ratio | 60dB(wide) 57dB(narrow) |
||||||||
Capture ratio | 1.0dB(wide) 2.0dB(narrow) |
||||||||
Distortion factor |
|
||||||||
Frequency characteristic | 20 Hz ~ 18000 Hz + 0.2 -0.8 dB | ||||||||
Antenna impedance | 75 Ω, 300 Ω | ||||||||
Stereo separation |
|
||||||||
Carrier leak | -70dB | ||||||||
Output voltage (400 Hz, 100% modulation) | Variable Output : 0 mv ~ 1200 mv Recorded output : 450 mV |
||||||||
Output impedance | Variable output : 1.8k Ω at maximum Recording Output : 2.7k Ω |
||||||||
<General> | |||||||||
Semiconductor used | 20 ic, 52 tr (5 fet), 47 di | ||||||||
Pwer | 100 VAC, 50/60Hz | ||||||||
Power consumption (Electrical Appliance and Material Control Law standard) | 9W | ||||||||
External dimensions | Width 435x Height 108x Depth 366 mm | ||||||||
Weight | 6kg |