More Information about KENWOOD L-01T FM STEREO TUNER VINTAGE HIGH END RARE SERVICED
Kenwood L-01T FM stereo tuner in full working order with a recent service, inspected inside and out and operates within specifications. The front panel backlighting has been updated to led, the original bulbs are increasing hard to find and likely to fail due to age. The unit is in good condition for age, a couple of scratches to the front bezel and some minor irregularities to the wooden cover. Finally the tuning knob is not the original one, however it is a close match to the original. This is an import unit that has been adjusted to the full 87.5 – 108.0 MHz FM bandwidth, as a result the original tuning scale doesn't corelate to the actual tuned frequency. Comes with a UK mains power adapter and no other accessories or cables. This is a rare high end tuner at a great price that performs at its best with a high gain outdoor antenna.
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FM stereo tuner pursuing non-magnetic material based on excellent circuit technology such as pulse count and sampling hold MPX.
The L-01T is the first tuner to use a non-magnetic housing.
The non-magnetic material used is almost the same as L-01A, the sub panel and back panel are made of new reinforced nylon with excellent impact resistance and durability, the side frame is made of aluminum case, and the bottom plate is made of wood.
In addition, oxygen-free copper with a purity of 99.96% is used for the structural material and the bus earth bar, and smoked acrylic is used for the front panel.
The independent power supply oscillator is carried in order to prevent sound quality deterioration through a power-source part.
The detection circuit and MPX circuit inevitably generate an audio signal in the + B line by the output impedance between the + B power supply and the ground. The signal component generated in + B is fed back to the local oscillator circuit via the power supply section, FM-modulates the frequency of the local oscillator circuit, becomes a noise component, and appears in the output.
The L-01T adopts an independent power supply oscillator that separates the power supply of the local oscillation circuit from the power supply of the detector and MPX circuit, prevents the feedback of the signal via the power supply from the detection circuit and MPX circuit, and is a clear FM signal. Is realized. The direct conversion system which inputs an input signal directly to a mixer stage without passing through an RF amplification part is adopted, and the excellent 2 signal characteristics and a wide dynamic range are obtained.The direct conversion system consists of triple tuning, a mixer, and two stages of IF amplifiers. The mixer is a balanced type using dual J-FETs selected in pairs, and the IF amplifier in the subsequent stage is also a push-pull amplifier using the same FET. This has secured a sufficiently wide dynamic range and has suppressed the occurrence of IM distortion in the IF stage.
Equipped with an RF selector, it can be used in the direct conversion position when there is sufficient input or when there is a station with a large output close to it, and in the high-sensitivity normal position when the input is small. I can do it.
In the normal position, a frequency linear high-precision 7-unit variable capacitor with a wide air gap is composed of a single-single-triple tune, and the RF amplifier has a DD-MOS type FET with a large power gain and a wide dynamic range, and a third cross-modulation. The high Gm J-FET which reduced the distortion greatly is used. And, the output of the third stage of triple tune is connected to the next stage (balanced mixer) with low impedance, and it is designed in consideration of impedance matching.
Moreover, the local oscillation circuit and the variable condenser are integrated, and the scale accuracy is improved according to the rotation angle of a variable condenser. Furthermore, the frequency drift due to the change of temperature and humidity is suppressed by blocking with three-dimensional wiring.
The pulse count system which further improved the waveform shaping part and the drift measures is adopted as a detection part.
Since the entire detection range over a wide band is straight, this method can reproduce the music waveform of a broadcasting station as it is as an output waveform, and is an excellent method that does not cause distortion in principle.
The double conversion system is adopted in order to maximize the feature of the pulse count detection system.
In this method, the intermediate frequency 10.7MHz obtained in the first IF is further converted to the second IF 1.96MHz. As a result, the relative frequency shift can be increased, so the wideband linear width obtained by pulse count detection is fully utilized, the detection efficiency is improved, and the SN ratio is greatly improved.
The sampling hold MPX circuit developed by KT-9900 is adopted, and the separation is improved sharply.
Since only the peak is sampled and held, there is little change in the amplitude of the 38kHz component when modulation is applied, and dynamic carrier leakage due to changes in the audio modulation level hardly occurs. Combined with the pilot canceller, the frequency characteristics of the low-pass filter in the final stage are greatly improved.
The synchro touch tuning method is adopted.
After tuning to the broadcasting station with the tuning knob, release the finger and the signal meter and tuning meter lights will turn off after about 2 seconds. During listening, only the tuning point of the dial scale, the operation indicator, and the stereo indicator are lit. Furthermore, since it has a built-in servo lock, there is no risk of tuning deviation once tuning is performed.
Also, if you always want to look directly at the meter or dial scale, you can switch between them with the switch on the back.
The clean subcarrier system and the pilot canceller are carried in the MPX part.
The clean subcarrier system prevents the audio signal from getting mixed into the switching signal and allows the pilot canceller to operate accurately without causing beat distortion.
The low output impedance design is made by utilizing the know-how gained by the direct drive amplifier system, which is the original form of the separate amplifier completed by the trio.
This has reduced the influence on the sound quality by the connected shielded wire and the input capacity of an amplifier.
The power supply section is 20VA on the local oscillation circuit side and 24VA on the other RF amplification circuit, detection circuit, and MPX circuit side, and the tuner transformer uses an extraordinarily large transformer to configure two power supplies. increase.
In addition, + 14V for the signal system of the front end / IF section, ± 16V for the MPX low frequency amplifier circuit, and + 12V for the local oscillation circuit. After rectification, a constant voltage power supply is installed for each block, and each block is installed. The interference between them is suppressed. Furthermore, a large-capacity electrolytic capacitor of 2,200 μF for + 14 V, 1,000 μF x 2 for ± 16 V, and 220 μF for + 12 V is arranged.