Audio Database

Image of A-150D
Commentary

A pre-main amplifier developed as a tri-angle drive system with the aim of improving the total balance of the amplifier.

In order to strengthen the power supply section, independent large power transformers are adopted for each of Lch and Rch of the power amplifier, and power is supplied from two transformers to each output stage and voltage amplification stage.
In addition, the power supply section of the equalizer amplifier is also equipped with a special transformer to supply current to the Lch and Rch channels.

Not only the power transformer is separated, but the construction itself also pursues the ideal of a separate amplifier. Not only the power transformer is used for the power amplifier section, but also the rectifier circuit and power capacitor are completely used exclusively for Lch and Rch. Furthermore, the layout of each component, wiring, radiator, etc. is completely separated to prevent signals from crossing each other. Thus, there is no interference between the left and right sides, and generation of intermodulation distortion is suppressed, and high separation is achieved.

By using tone control and line-straight circuit to jump mode, excellent resolution and transparency are obtained, and the ability of source like CD is demonstrated.

To cope with sudden impedance changes in digital sources with sharp peak components, the Lch and Rch power supplies are equipped with a 20,000 μ F single-channel large-capacity power supply capacitor.
In addition, three power transistors are connected in parallel for each channel in a triple push-pull configuration, achieving a current supply capacity of 32A, two to three times that of a normal amplifier.

It is equipped with non-switching circuit TypeII which is an improvement of non-switching circuit in which switching distortion does not occur in principle. The range of 0 switching distortion is further expanded and the bandwidth is further widened.
It also stabilizes the idle current, which is constantly drifting due to changes in the outside air temperature, or immediately after the power switch is turned on or when a large signal is input, and suppresses thermal distortion caused by this idle current.
Furthermore, by detecting and correcting the difference between the input and output signals, the nonlinear distortion of the output stage has been reduced to approximately 1/30.

Each part is carefully selected. Copper lead wires are used for major components such as capacitors and resistors. oxygen-free copper wires are also used for major wiring materials and extra-thick power cords. Non-magnetic tinning is also used for input / output terminals.
In addition, the speaker terminal uses a vise type to securely crimp the cable to supply current without loss, and the earth point is separated into a power supply system and a signal system. We repeatedly pursue technical details and conduct thorough trial listening.

A hybrid MC transformer has been adopted to greatly improve the high-frequency characteristics by reducing the step-up ratio by half.
As a result, -frequency playback with excellent phase characteristics, low DCR (direct current resistance), and effective warping.
Two impedance values are also provided to enable matching with various types of cartridges.

The input terminals have a Line 5. Especially in the CD-position, the shortest wiring is used in terms of circuit, and high-quality parts are used. Specifications give priority to digital.
It is also equipped with two tape monitors for a total of seven inputs and outputs.

The side wood in the picture was sold separately.

Model Rating
Type Non-switching premain amplifier
Effective power
20 Hz to 20 kHz : 150W + 150W (6 Ω, both channel drive)
120W + 120W (8 Ω, both channel drive)
1kHz: 200W + 200W (4 Ω, both channel drive)
160W + 160W (6 Ω, both channel drive)
130W + 130W (8 Ω, both channel drive)
Harmonic distortion factor (20 Hz to 20 kHz) 0.003% (at effective output)
Intermodulation distortion factor (50 hz : 7 khz = 4 : 1) 0.003% (20 Hz to 20 kHz, 120W, 8 Ω)
Output bandwidth 5 Hz ~ 60 kHz (IHF, both channel drive, THD0.01%)
Output terminal Speaker (4 Ω ~ 16 Ω) : A, B, A + B
Tape Rec:150mV
Damping factor 100 (20 Hz ~ 20 kHz, 8 Ω)
Input Sensitivity / Impedance Phono MM : 2.5mV/50k Ω
Phono MC : 0.15mV/3 Ω, 0.25mV/40 Ω
CD, Tuner, AUX, Tape Play1, 2 : 150mV/30k Ω
Phono maximum allowable input (1 kHz, THD0.003%) MM:250mV
MC:18mV
Frequency characteristic Phono MM : 20 Hz to 20 kHz ± 0.2 dB
CD, Tuner, AUX, Tape Play : 2 Hz to 100 kHz + 0 -3dB
Signal-to-noise ratio
(IHF, A-network, short circuit)
Phono MM:90dB
Phono MC:76dB
CD, Tuner, AUX, Tape Play : 110 dB
Stereo separation 90dB(1kHz)
Tone control Bass : ± 8 dB (100 Hz)
Treble : ± 8 dB (10 kHz)
Filter Low : 15 Hz, 6dB/oct.
Power supply voltage 100 VAC, 50Hz/60Hz
Power consumption (Electrical Appliance and Material Control Law) 350W
External dimensions Width 420x Height 151x Depth 427 mm
Weight 16.6kg
Sold Separately Sidewood JA-A120 (¥ 4,000)