YAMAHA CT-1000

Commentary

FM/AM tuner equipped with Yamaha's original NFB, PLL, and MPX circuits.

A high-precision wide-gap five series varicon and a low-noise dual-gate MOS FET with excellent frequency characteristics are used in the high-frequency stage and mixer stage for the front-end to improve various disturbance rejection characteristics. In addition, a dedicated IC incorporating a constant-voltage power supply and constant-current power supply is used in the local oscillator circuit for a highly stable design against disturbances.
The high-precision wide-air-gap 5-series variable capacitor adopted in the CT-1000 has double the air gap to reduce the change in capacitance due to changes in temperature and other factors. In addition, the variable capacitor itself has been precisely calibrated in the manufacturing process by increasing the processing accuracy of the variable capacitor itself, thus eliminating the need for external calibration of the trimmer capacitor, which was required in the conventional one.

A newly developed 6-element low-loss and low-spurious ceramic filter is used for the IF filter, and an L/C/R-based impedance-transform-type phase distortion compensation circuit is also mounted.
The IF amplifier uses an IC-type differential amplifier x2 = 6-stage differential amplifier circuit with a current limiter to achieve excellent interference rejection characteristics and low distortion rate characteristics.
A wide-band balanced deformation ratio detector is used for the detection circuit.

The MPX circuit is an NFB-PLL-MPX circuit that applies NFB (negative feedback) like audio amplifiers to a subcarrier generation circuit that uses Yamaha's original demodulation circuit and PLL-IC. This circuit uses the feedback amplifier gain for 100% negative feedback to reduce distortion and noise generated inside the PLL IC.
The CT-1000 does not use a filter to remove the pilot signal. Instead, it uses a pilot cancellation circuit that cancels the pilot signal at the entrance of the decoder with the same 19 kHz reverse sine wave (a sine wave converted from the square wave generated by the PLL). This enables wide-band playback extending to 18 kHz.

In order to cope with the low distortion factor of the high frequency system, the amplifier element through which the signal passes is minimized even in the audio system. Basically, only one stage buffer amplifier for each input and output is provided outside the NF loop of the NFB, PLL and MPX circuit.
The input buffer amplifier is composed of a wide-band DC amplifier, and the output buffer amplifier employs an active load emitter follower combined with an LC active low-pass filter.

It is equipped with an OTS mechanism to firmly maintain the tuning point.
The Oputimum Tuning System (OTS) is a system that combines a detuning point detection amplifier, an electronic touch switch, and an indicator using LED. When the tuning knob is touched during tuning, the AFC is turned off by the action of the electronic touch switch, making tuning easier. When the station is tuned during tuning, the OTS/STATION indicator lights faintly. When the station is tuned accurately and the knob is released, the OTS automatically differentiates and the OTS/STATION indicator lights brightly to maintain the best tuning point.

Equipped with interference detection method signal strength / quality meter.
The meter can indicate a wide input level of 3 μ V to 3 mV by installing a disturbance detection amplifier and an AGC amplifier in two stages. The meter can also indicate disturbance such as multipath and fading as a decrease in indication value or wamble without saturation to a strong input by a unique disturbance detection method.

The AM tuner section uses a single RF stage, a differential mixer and a peak-to-peak detector to reduce distortion.

Equipped with 3 μ V ⇔ 30 μ V switching type muting circuit which prevents pop noise at both tuning and detuning.

Equipped with Rec Cal circuit that is convenient for air check.

Model Rating

Type	FM/AM stereo tuner
FM Tuner Section
FM practical sensitivity (IHF, 300 Ω)	Mono : 1.9 μ V/10.8 dBf
Image interference ratio	110dB
IF interference ratio	110dB
Capture ratio	1.0dB
Effective selectivity (IHF)	85dB
Signal-to-noise ratio	mono:80dB stereo:75dB
Total harmonic distortion rate (1 kHz)	mono:0.07% stereo:0.07%
Stereo Separation (1 kHz)	52dB
Frequency characteristic	30 Hz ~ 15 kHz + 0. 3-0. 5 dB
Subcarrier suppression ratio	70dB
<AM Tuner Section>
Practical sensitivity	300 μ V/m (49dB/m)
Selectivity (IHF)	30dB
<General>
Accessory circuit	FM muting switch OTS High filter Output level volume Rec calibrator Signal Strength/Quality Meter
Power supply voltage	100 VAC, 50Hz/60Hz
Rated power consumption	8W
External dimensions	Width 461x Height 170x Depth 408 mm
Weight	7.6kg