Accuphase T-108

Commentary

This is a synthesizer FM stereo tuner that has been developed technology to realize the ultimate grade as a tuner.

Tuning for channel selection is achieved by using a crystal oscillator, with less deviation due to time or temperature change, and with electronic tuning, almost no modulation distortion or noise due to external vibration occurs.

Memory for up to 16 stations is available for multi-station operation.
If you need to turn on a filter or change the selectivity depending on the station where the signal is weak, you can set a function corresponding to the signal condition of the station in advance.

In addition to memory tuning, a manual tuner using a rotary knob of pulse tuning type is mounted.
It was developed especially as the main electronic tuning method, and pulses are generated by a radial slit attached to the shaft of a rotary knob, and the tuning frequency is controlled by counting these pulses.

The front-end input and amplifier stages are each composed of a double-tuned configuration, and the frequency-conversion mixer is a differential-FET balanced modulator using a balloon transformer to prevent interference due to Dainyu interference.
In addition, since a PIN diode attenuator is mounted and the transmission tower operates as a variable attenuator for a large excess input near the transmission tower, no interference or distortion occurs in any region.

By combining Acuphase's original DGL detector with specially selected group-delay flat IF filter, stable and low distortion characteristics are obtained.
The DGL detection method focuses on the delay time of the output of a high-speed logic IC. Nineteen of these circuits are connected in series to minimize distortion and optimize S/N by delaying the phase angle by 114 degrees. The group delay signal and the input signal are added to an exclusive OR circuit. The potential between the two signals is selected to open and close the circuit. The differential gain is digitally detected and an audio signal is extracted. Since the linear region of the delay circuit is extremely wide at ± 2.5 MHz and moreover it is a non-adjustable circuit, stable and excellent linear differential gain characteristics can be obtained.
Two sets of IF filters, Normal and Narrow, are used. When adjacent interference is intense, switching to Narrow enables sharp reception with an emphasis on selectivity.

The stereo demodulation section uses the pilot signal for synchronization included in the input signal to lock the internal oscillation circuit with the PLL circuit to obtain an accurate 38 kHz switching signal.
The T-108 employs a combination of a ceramic resonator and a variable positive and negative reactance circuit that can be controlled by the control voltage for the internal oscillation circuit of this PLL, and it can obtain accurate switching signals in a narrower lock frequency range than conventional ones.
For this reason, this circuit realizes the non-adjustment of the stereo demodulation circuit and can maintain the characteristics over a long period of time. Moreover, there is almost no change in the degree of separation due to temperature change or line voltage fluctuation.
In addition, since the lock frequency range is narrower than before, beat distortion at high frequencies is reduced.

The output terminal is equipped with the first balanced output circuit of the tuner.

The meter can be used to check the input signal meter and multi-path with a switch.
Multipath indicates that you can receive high-quality signals with minimum multipath if the meter indicator is within the clear mark range.

It is equipped with a noise filter to reduce noise in stereo stations with weak radio waves, a muting switch to remove inter-station noise, a mono switch to force monaural, and an output level control to adjust the volume to other program sources.

It comes with a remote control so that it can be operated from a distance.

The exterior is finished with a traditional champagne gold scratch hairline finish supported by natural Persimmon boards on both sides.

Model Rating

Type	Synthesizer FM tuner
MonAural Characteristics
Receiving frequency	76.1 mhz to 89.9 mhz
Practical sensitivity	11dBf(IHF)
S/N 50 dB sensitivity	17dBf(IHF)
Standing-wave ratio	1.5
S/N (80 dBf input, A-correction)	90dB
Total harmonic distortion factor (80 dBf input ± 75 kHz shift, Normal)	20Hz:0.02% 1kHz:0.02% 10kHz:0.02%
IM distortion factor	0.01% (80 dBf input, ± 75 kHz shift)
Frequency characteristic	10 Hz ~ 16000 Hz + 0 -1.0 dB
Two signal selectivity (IHF)	Disturbance wave Normal Narrow 400kHz 70dB 100 dB or more 300kHz 30dB 100dB 200kHz 10dB 40dB
Capture ratio	1.5dB
RF intermodulation	80dB
Spurious interference ratio	120dB
Image ratio	100dB
AM suppression ratio (65 dBf input)	80dB
Subcarrier suppression ratio	70dB
SCA interference ratio	80dB
Output voltage (± 75 kHz deviation)	1.0V
Stereo Characteristics
Sensitivity	S/N 40 dB sensitivity : 29 dBf (IHF) S/N 50 dB sensitivity : 37 dBf (IHF)
S/N (80 dBf input, A-correction)	85dB
Total harmonic distortion factor (80 dBf input ± 75 kHz shift, Normal)	20Hz:0.04% 1kHz:0.04% 10kHz:0.04%
IM distortion factor	0.03% (80 dBf input, ± 75 kHz shift)
Frequency characteristic	10 Hz ~ 16000 Hz + 0 -1.0 dB
Stereo separation factor	100Hz:50dB 1kHz:50dB 10kHz:40dB
Stereo switching input voltage	20dBf
<General>
Antenna	75 Ω unbalanced (with 300 Ω balanced converter)
Tuning system	Quartz synthesizer system 16-station random memory tuning
Detection system	DGL method
Output impedance	Balanced (Balanced XLR type) : 200 Ω (100 Ω / 100 Ω) Unbalanced Fixed output : 200 Ω Controlled (variable output) : 1.25k Ω (maximum)
Meter	Signal strength, multi-path switching
Semiconductor used	Transistor : 15 FET : 5 pcs IC : 32 Diode : 36 units
Pwer	AC100V/117V/220V/240V, 50Hz/60Hz
Power consumption	15W
External dimensions	Width 475x Height 115x Depth 351 mm
Weight	9.4kg