Audio Database
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Commentary

Accuphase's pure Class-A monophonic power amplifier was born in pursuit of the ideal of music reproduction.
We use all of the development technology we have accumulated since our establishment and the highest grade materials to complete our products.

In the output stage, an N-channel power MOS FET and a P-channel power MOS FET are each connected in 10-parallel, and the two are bridged together.
Although the rated output of 8 ohms is 100W, a total of 40 power MOS FETs are used in two units, and the total drain loss is 4kW, which is an overwhelming margin.
In order to cope with the large heat generation generated by pure Class A operation, we have made it possible to use the device in a variety of ways. The power amplifier assembly is made up of a thick aluminum block with the output elements, and then the block is attached to an extra-large heat sink made of extruded aluminum.

Two unit amplifiers with push-pull drive in all stages are connected to the bridge, and the balanced configuration suppresses distortions generated inside the amplifiers and noise coming in from outside.
When balanced, signals are added to each of the + and - inputs, and the signals appear in opposite phases to each other at the output to create a fully balanced output.
When unbalanced, the signal is input to the + input terminal and the - input terminal is grounded.
In this way, no extra circuitry, such as a converter, is added at all, enabling homogeneous amplification in both balanced and unbalanced situations.

The input stage has Accuphase's original balanced pure complementary push-pull configuration, and the + (non-inverted) and - (inverted) input circuits use FET buffers with high input impedance and low impedance outputs, respectively.
The important part of this input circuit has been converted into a large hybrid IC of 60 mm x 35 mm.
The target circuit is placed on top of the alumina magnetic base, which improves temperature characteristics and noise characteristics, and achieves high performance, long-term stability and high reliability.
The IC is covered with a thick aluminum material to block out external influences.

The part where the signal passes through is made of copper.
In addition, gold plating is applied on top of this to reduce skin resistance and smooth the flow of current.
Especially for power amplifiers, oxygen-free cylinders are used to handle large currents, and gold plates are applied to these as well.
In addition, high purity wire is used for the shield cold around the attenuator to improve the sound quality.

In order to cope with the heat generated by Class A amplifiers using natural air cooling, a large heat sink is required, with a total encompassing area of 16.4 liters and a total weight of about 20 kg on both sides.
This heat sink is finned for natural air cooling and has a handle in the center for resonance damping to prevent squealing.
The chassis is also made of 9mm-thick aluminum and has a strong structure.

The power supply transformer is a high-efficiency toroidal structure, which is fixed to the die-cast aluminum case using a filler material with good thermal conductivity and high anti-vibration effect to block the influence to the outside.
The electrolytic capacitor for smoothing is similarly enclosed in a die-cast aluminum case with a 4mm thick die-cast aluminum case filled with a special fixing material for the electrolytic capacitor.
This increased rigidity makes it difficult for external influences to be transmitted.

It uses ultra-large speaker terminals that can accommodate thick speaker cables.
The material is machined from solid brass and plated with gold, and then covered with a molded cap for insulation purposes.
Two sets of these are mounted in parallel so that they can be used with bi-wiring speakers.
The electrode is made of a 2 mm thick oxygen-free copper plate pressed into a gold plate.

It is equipped with a large output meter that is convenient for monitoring.
Logarithmic compression allows you to see a wide dynamic range all at once, while capturing peaks so you know exactly what power you're getting.
It also has a switch to turn off the meter operation and proof.

Model rating
Model Monaural Power Amplifier
Continuous average output
(between 20Hz and 20kHz)
2 ohm load:400W
4 ohm load:200W
8 ohm load:100W
16 ohm load:50W
Full harmonic distortion
(Between 0.25W and continuous average output)
2ohm load:0.02%
4 to 16 ohm load: 0.01%
IM skewness 0.003%
Frequency response 20Hz to 20000Hz, +/-0dB(at continuous average output, level control MAX)
0.5Hz to 150000Hz, +0 -3.0dB(at 1W output, level control MAX)
0.5Hz to 80000Hz, +0 -3.0dB(at 1W output, level control -6dB)
Gain (gain) 28dB
Load impedance 2 to 16ohm
Dumping Factor 250(8ohm load, 50Hz)
Input sensitivity (8 ohm load) Continuous average output:1.13V
At 1W output:0.12V
Input impedance Unbalanced:20kohm
Balance:40kohm
S/N(A-correction) 120dB (at short input and continuous average output)
Power Meter Logarithmic compression peak level display
Direct reading of output at the dB scale and 8 ohm load
Semiconductors used 16Tr, 44FET, 10IC, 44Di
Power 100V, 117V, 220V, 240V, 50Hz/60Hz
Power consumption Without input:350W
Electrical Appliance and Material Control Law:480W
At 8 ohm load rated output:350W
Exterior Dimensions W475 x H240 (including legs) x D553mm (including handle)
Weight 57.0kg