Audio Database


Accuphase P-550
580,000 yen(April, 1994 release)


Stereo power amplifier which planned exact energy supply by the reduction in the impedance of an output circuit, and a powerful power-source part.

It excelled in many characteristics, such as a frequency response, a current gain linearity, switching, and the power transistor for audios of the Oide power multi-emitter structure of the collector loss 130W and collector current 15A is adopted as an output element.
It is this element 10 - High power is realized by carrying out parallel connection.
Moreover, operation to heat had adopted the power MOS FET of the negative characteristic as the drive stage, the power transistor and heat inclination of the right characteristic were offset, and stable operation is realized.

The current feedback type magnification circuit which returns an output signal in the form of current is developed and carried in the magnification circuit.
The basic principle of this circuit lowered the impedance of the input terminal by the side of a return first, has detected current, carries out I-V conversion (current-voltage conversion) of that current with a transformer impedance amplifier, and makes an output signal.
Since the impedance of a return input portion is very low in this circuit, it is hard to generate phase rotation and, as a result, there is almost no necessity for a phase guarantee. For this reason, it excelled in dynamic characteristics, such as a standup, and the improvement of sound quality is achieved.
Moreover, in this circuit, even if it changes a profit, a frequency response hardly changes.

carry the changeover switch -- it can be used also as monophonic power amplifier by bridge connection.
The signal of an inversion phase is mutually inputted as bridge connection on the same voltage as the amplifier of two channels, it is the method of connecting a speaker to the output end of both amplifier, and the Oide power and a sound quality improvement can be aimed at by this.

The balance input terminal which cannot receive visitor guidance noise other than the usual imbalanced input easily is carried in the input terminal. In P-550, the system which carries out a signal input as it is to the non invert (+) of an input circuit and an invert (-) input is adopted.

Copper with high purity is used for the portion which a signal passes, and plate-ization with gold is performed on this.
It is given to a printed board Copper-foil side, a grounded plate, the wiring board for a ground of the input unit, the bus bar that supplies current to a power transistor, the input terminal, the speaker terminal, etc. in P-550. In particular, one about 10 times [ usual ] the thickness of this is given to a frequently-used input terminal, and improvement in reliability is aimed at.

The large-sized Troy Dahl type transformer of 1200VA is adopted as a power-source part.
Moreover, two large scale types of 47,000 micro F / 100WV (the amount of electric charges of 4.7C) are carried in the electrolytic condenser.

The large-sized analog-type power meter is carried.

The large-sized speaker terminal also corresponding to a very-thick cable or a banana plug is adopted as an output terminal.
The speaker terminal also supports those with two line, and bi-wiring connection.

Internal Power
Power Block Golden Speaker

Rating of a mode
Form Stereo power amplifier
Continuation average output
(20Hz - 20kHz)
At the time of stereo specification : 550 W/ch (2ohms)
420 W/ch (4ohms)
270 W/ch (8ohms)
At the time of monophonic specification :
(Bridge connection)
1100W (4ohms)
840W (8ohms)
At the time of stereo specification : 0.05% (2ohms)
0.02% (4ohm-16ohm)
At the time of monophonic specification : 0.02% (4ohm-16ohm)
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: 4ohms - 16ohms
Dumping factor At the time of stereo specification: 500
At the time of monophonic specification: 250
Input sensitivity (8-ohm load)
At the time of stereo specification : 1.85V (at the time of a rated continuation average output)
0.12V (at the time of 1W output)
At the time of monophonic specification : 3.26V (at the time of a rated continuation average output)
0.12V (at the time of 1W output)
Input impedance Imbalanced Input: 20kohm
Balance input: 40kohm
S/N (A compensation) 123dB (at the time of input short-circuit and a continuation average output)
Power output meter Logarithm compression type
- 50dB - +3dB, and an output Direct-reading scale
Power source AC100V, 50Hz/60Hz
Power consumption 200W (at the time of no inputting)
980W (Electrical Appliance and Material Control Law)
920W (at the time of an 8-ohm load Output power)
The maximum Dimensions Width 475x height 211x depth of 444mm
Weight 33.0kg