Audio Database


Accuphase P-450
380,000 yen(April, 1997 release)


The element of the highest grade which concentrated the technology of the power amplifier which the Accuphase has accumulated and examined part each, and the stereo power amplifier which adopted the current feedback magnification circuit.

The newly developed high power transistor of the collector loss 150W and collector current 15A is adopted as an output stage.
This element has the feature excellent in many characteristics, such as a frequency response, a current gain linearity, and switching, constituted this from a 4-parallel push pull, is attaching to the large-sized heat sink made from aluminum die-casting, performed efficient heat dissipation processing, was stabilized and has realized Oide power.

The current feedback (current feedback type) magnification circuit which returns an output signal in the form of current is adopted.
The principle of operation of this circuit lowers the impedance of the input terminal by the side of a return first, and detects current. I-V (current-voltage) conversion of the current is carried out with a transformer impedance amplifier, and the output signal is made.
In this circuit, since the impedance of a return input portion is very low, it is hard to generate phase rotation and there is almost no necessity for phase compensation. For this reason, since many characteristics are sharply improvable by a little NFB, it excelled in dynamic characteristics, such as a standup, and sound quality has been improved by natural energy response.

The changeover switch is carried and it can be used as monophonic power amplifier by bridge connection.
Bridge connection is the method of inputting the signal of an inversion phase mutually on the same voltage as the amplifier of two channels, and connecting a speaker to the output end of both amplifier. It is possible for this to acquire a sound quality improvement and the Oide power.

In order to eliminate the disturbance noise mixed from the signal cable between apparatus, the balance input terminal is prepared in the input terminal.

The large-sized toroidal transformer of about 660 VA is adopted as a power-source part.
The toroidal transformer has the features, like impedance is very low, it is small, and conversion efficiency is high in order to coil thick copper wire around a doughnut-like core. The transformer of a super ring type is adopted, the section of an iron core is close to a circle, a coil can also be rolled closely circularly, especially in P-450, since adhesion nature is good, there are few losses, weight is made lightly, the leakage flux at the time of load is small, and a roar and vibration are also small. Moreover, the feature that iron loss and in rushes current are small also has the cross-sectional area of an iron core by enlarging the rate of a bulk density of copper wire small.
Two large scale types of 47,000 micro F / 80WV are carried in the aluminum electrolytic capacitor.

Copper with high purity is used for the parts which a signal passes, and plate-ization with gold is performed from on the in P-450. Improvement in sound qualities, such as a grounded plate, a capacitor terminal, an input terminal, a speaker terminal, etc. in which big ripple current flows by this, is aimed at.
On the usual golden plate, since the input terminal especially with high frequency in use is thin, it performs processing for industrial apparatus in which one about 10 times the thickness of this was given, and is aiming at improvement in reliability.

The large-sized analog-type power meter which can carry out the Direct reading of the large power range by logarithm compression is carried.
The switch which turns on and off operation and lighting of meter is also equipped.

The large-sized speaker terminal also corresponding to a very-thick speaker cable is adopted.
Brass Naked material is used for a material, it begins to delete, a golden plate is formed, and the mould cap of the insulated purpose is put on it.

Rear Golden Power
Protection Use Power Block

Rating of a mode
Form Stereo power amplifier
Rated continuation average output
(20Hz - 20kHz)
At the time of stereo specification : 400 W/ch (it restricts to 2 ohms and a music signal)
300 W/ch (4ohms)
200 W/ch (8ohms)
At the time of monophonic specification :
(Bridge connection)
800W (it restricts to 4 ohms and a music signal)
600W (8ohms)
At the time of stereo specification : 0.05% (2-ohm load)
0.02% (4ohms - 16-ohm load)
At the time of monophonic specification : 0.02% (4ohms - 16-ohm load)
IM distortion 0.003%
Frequency response 20Hz-20kHz+0 -0.2 dB (at the time of a rated continuation average output)
0.5Hz-160kHz+0 -3.0dB (at the time of 1W output)
Gain 28.0dB (at the time of a stereo / monophonic specification)
Load impedance At the time of stereo specification: 2ohms - 16ohms
At the time of monophonic specification (bridge connection): 4ohms - 16ohms
Dumping factor At the time of stereo specification: 400
At the time of monophonic specification: 200
Input sensitivity (at the time of 8-ohm load)
At the time of stereo specification : 1.59V (at the time of a rated continuation average output)
0.11V (at the time of 1W output)
At the time of monophonic specification :
(Bridge connection)
2.76V (at the time of a rated continuation average output)
0.11V (at the time of 1W output)
Input impedance Imbalanced Input: 20kohm
Balance input: 40kohm
S/N (A compensation, input short-circuit) 120dB (at the time of a rated continuation average output)
Power output meter Logarithm compression type peak level display
dB scale and the output Direct reading at the time of 8-ohm load
Power source AC100V, 50Hz/60Hz
Power consumption 125W (at the time of no inputting)
450W (Electrical Appliance and Material Control Law)
630W (at the time of an 8-ohm load Output power)
The maximum Dimensions Width 475x height 211x depth of 465mm
Weight 30.6kg