LUXMAN T-12

Commentary

FM stereo tuner using quartz lock system.

Equipped with an accu-touch mechanism.
This mechanism uses the control voltage of the quartz lock circuit to detect an accurate center point, which is then mechanically locked. When you turn the tuning knob slowly to look for a broadcasting station, the knob is temporarily locked (approximately 2 seconds) with a sense of response, and it stops at the exact same point including the RF stage.
Generally, FM tuners that use the quartz lock system have the advantage of being able to ensure extremely stable reception even under changes in external conditions such as temperature. However, this system operates to keep only the intermediate frequency constant, and the RF stage does not benefit from this system. In addition, depending on the tuning operation, a tuning error of up to 100 kHz occurs.
By adopting the Accu-touch mechanism, this problem is solved and the advantage of the quartz lock system is utilized.

It uses a loop gain equalizer that maintains a constant lock range across the receiving scale from 76 mhz to 90 mhz.
This detects whether the receiving frequency is high or low and controls the control ability of the frequency control element to keep the optimum lock range at all times over the receiving scale.
In the conventional quartz lock system, since the capacitance of the control element connected to the local oscillation circuit is constant, the influence on the local oscillator circuit is greater when the local oscillation frequency is higher than when it is low. Therefore, when the lock range is adjusted to be appropriate at a point with low reception frequency, the lock range becomes too wide at a point with high reception frequency. One station occupies a considerable width on the dial scale, and the pointer can be received anywhere within this width. This resulted in the tracking error of the RF stage.
To keep the locking controlling force at the highest level, a loop gain equalizer is used.

It uses a Dynamic Kick System, and even if the power is turned off with the quartz lock engaged, it will automatically return to the locked state when the power is turned on.
In the conventional quartz lock method, when the power is turned off, the loop of the PLL circuit is cut off. Therefore, when the power is turned on again, it was necessary to reset the tuning to the locked state. This problem has been fixed.

For the front end, a 5-row varicon dedicated for FM is adopted to take advantage of the excellent characteristics after the IF stage. In addition, by increasing the selectivity of each high-frequency amplifier circuit, sufficient interference removal capability is ensured.
To further reduce the distortion factor, we have adopted a quad Racea detector circuit and a multiplex circuit with a pilot signal canceller to improve the phase characteristics of the low-pass filter.

DC amplifier configuration is used for the audio stage.

The IF stage has a 2-stage bandwidth switching function.
At the wide position, ultra-low-frequency distortion characteristics are achieved by two sets of LC-type block filters with excellent phase characteristics, and at the narrow position, high selectivity characteristics are achieved by combining a block filter with a ceramic filter.

Model Rating

Type	FM tuner
Practical sensitivity of IHF	1.7 μ V/9.8 dBf
50 dB quieting sensitivity	3.2 μ V/15.2 dBf
Two signal selectivity	90 dB (narrow, ± 400 kHz) 60 db (narrow, 300 khz, * listed in separate catalog)
Signal-to-noise ratio	80dB
Frequency characteristic	20 hz to 17 khz -0.5 db (mono & stereo)
Distortion factor	Wide 0.05% (1 kHz, mono) 0.06% (1 kHz, stereo) 0.05% (100 Hz, mono) 0.07% (100 Hz, stereo) 0.07% (6 kHz, mono) 0.1% (6 kHz, stereo)
Capture ratio	wide:0.8dB narrow:2dB
Spurious characteristic	100dB
IF interference rejection ratio	100dB
Image ratio	100dB
Amplitude modulation suppression	62dB
Stereo separation	50 dB (wide, 1 kHz) 45 dB (wide, 100 Hz) 45 dB (wide, 6 kHz)
Output	1V(fix.)
Output impedance	100 Ω
Attachment	Tuning lock mechanism IF bandwidth switching Multipath check circuit Test tone circuit for recording Center indicator Signal strength indicator
External dimensions	Width 438x Height 78x Depth 322 mm
Weight	7.0kg