TRIO L-07TII

Commentary

FM stereo tuner using pulse counting method.

It uses the pulse counting method, which is characterized by low distortion due to linear detection and high stability due to no adjustment position.
A frequency-modulated wave is converted into a square wave through a limiter. The pulse obtained through a differentiation circuit is used to trigger a monostable multi-circuit to obtain an output with the same pulse width. The output is applied to an integrator circuit to extract a demodulated signal.
The L-07TII is capable of 3.92 MHz linear detection and maintains a low distortion rate even with slight detuning due to linear detection.

In order to take full advantage of the low distortion rate obtained with the pulse count detection stage, we have adopted SAF, which can design the amplitude and phase characteristics independently and each to an arbitrary best point.
This SAF has a constant delay characteristic (linear phase characteristic) and achieves a low distortion factor over a wide band by designing the best point for amplitude characteristic.
In addition, unlike the conventional normal electrode type SAF, the driving electrode is "weighted" and the spurious, which was a defect of this type of filter, is greatly improved.
In addition, lead titanate (PZT), which is extremely resistant to aging and environmental changes, is used as the material, and it is carefully shielded by a metal case. Thus, deterioration of characteristics such as distortion rate and noise caused by external noise and interference with external circuits is suppressed, and characteristics are fully exhibited.

In order to make the best use of the pulse counting method, we have adopted a double conversion method that converts from the first IF 10.7 MHz to the second IF 1.96 MHz.
By increasing the relative frequency shift, the detection efficiency has been improved and a sufficient SN ratio has been achieved.

It is designed not only to increase the selectivity at the front end, but also to improve the filter characteristics, improve the phase characteristics, and prevent distortion and phase rotation at the RF stage.
The varicon is composed of a single-triple-double type of frequency number line 7 series varicon with built-in oscillation circuit. In addition, a DD-MOS type FET (SD 306) with a wide range of linearity and low noise factor (NF) is used in the RF section.
By improving the accuracy of the varicon and reducing the tracking error, the RF band characteristic is improved and the change of the characteristic by changing the frequency is suppressed.
By using three dimensional wiring for the local oscillator circuit, installing a buffer amplifier, and shielding with a case, the stability of the local oscillator part, which is a major element of stable reception, is improved and frequency drift due to changes in temperature and humidity is suppressed.

Two stage switching of the IF band is installed in order to demonstrate the best reception characteristics according to all reception conditions.
Sound quality oriented listening is used in the WIDE position. With the SAF2-stage configuration, a low distortion rate of 0.045% (1 kHz ・ STEREO) has been obtained with the adoption of the pulse count method.
Use the NARROW position to listen in areas with poor reception conditions. county High selectivity characteristics of 100 dB (400 kHz) and 60 dB (300 kHz) have been obtained with a three stage 12-element phase linear 4-element filter with excellent delay characteristics.

The MPX section has a two stage PLL loop filter and uses a clean subcarrier system that prevents the high-frequency components of the main and sub signals from entering the PLL pilot signal detection circuit, thereby preventing the tuner's unique high-frequency distortion (beat distortion) that occurs when receiving FM stereo broadcast transmission.
In addition, since a pilot canceler circuit is built in to cancel out the pilot signal, frequency characteristics are greatly improved up to the high frequency range, and at the same time, subcarrier suppression ratio is also obtained.

Equipped with a linear scale electrolytic strength indication type signal meter that can accurately read the strength of input radio wave from 0 db to 80 db (10 mv) large input.
This circuit also performs multipath detection simultaneously, resulting in a design with a wide multipath detection range.

A high-slew rate operational amplifier is used in the audio amplifier section.

Uses a large cut core transformer with good regulation, two capacitors of 3300 μ F, and one capacitor of 2200 μ F.
For constant voltage control, a full-operation amplifier is used to improve sound quality.

Model Rating

Type	Pulse counting FM stereo tuner
FM Tuner Section
Receiving frequency range	76 MHz to 90 MHz
Antenna impedance	300 Ω equilibrium 75 Ω unbalance
Sensitivity	1.7 μ V (IHF), 9.8 dBf (new IHF)
SN ratio 50 dB sensitivity	Mono : 3.0 μ V (IHF), 14.7 dBf (new IHF) Stereo : 35 μ V (IHF), 36 dBf (new IHF)
Distortion factor (100% modulation)	mono 100Hz: 0.04% (WIDE), 0.04% (NARROW) 1kHz: 0.04% (WIDE), 0.13% (NARROW) 6kHz: 0.06% (WIDE), 0.27% (NARROW) 15kHz: 0.05% (WIDE), 0.05% (NARROW) 50 Hz to 15 kHz : 0.06% (WIDE), 0.27% (NARROW) stereo 100Hz: 0.05% (WIDE), 0.2% (NARROW) 1kHz: 0.045% (WIDE), 0.15% (NARROW) 6kHz: 0.06% (WIDE), 0.25% (NARROW) 15kHz: 0.35% (WIDE), 0.9% (NARROW) 50 Hz to 15 kHz : 0.1% (WIDE), 0.4% (NARROW)
SN ratio (100% modulation 1 mV input)	mono:85dB stereo:80dB
Image interference ratio	120dB
Selectivity	WIDE:35dB NARROW : 100 dB (400 kHz), 60 dB (300 kHz)
IF interference ratio	120dB
Spurious interference ratio	120dB
AM suppression ratio	65dB
Capture ratio	WIDE:0.8dB NARROW:1.4dB
Subcarrier suppression ratio	73dB
Stereo separation	1kHz: 55 dB (WIDE), 50 dB (NARROW) 50 Hz to 10 kHz : 45 dB (WIDE), 38 dB (NARROW) 15kHz: 40 dB (WIDE), 32 dB (NARROW)
Frequency characteristic	20 Hz to 16 kHz + 0.2 dB -0.5 dB
Output and Impedance
FM (1 kHz, 100% modulation)	1V/1k Ω
Multipath	Vertical : 0.02V/1k Ω (1 kHz, 30% modulation) Horizontal : 0.4V/10k Ω (1 kHz, 100% modulation)
<General>
Rated power consumption	28W (Display based on Electrical Appliance and Material Control Law)
Pwer	100 VAC, 50/60Hz
External dimensions	Width 480x Height 100x Depth 336 mm
Weight	6.9kg