Accuphase A-45

Commentary

It is a pure A class stereo power amplifier developed by following the design technology as an amplifier located between A-60 and A-30.

The whole amplifier is constructed using the latest Instrumentation Amplifier method.
In this system, the signal path from the input terminal to the power amplifier stage is fully balanced, and not only is it excellent in various characteristics such as CMRR (Common Mode Rejection Ratio) and distortion factor, but it is also resistant to environmental changes such as external noise, and stability and reliability as a power amplifier are improved.

The amplifier is equipped with an MCS + circuit and a current feedback amplifier circuit to further improve electrical performance.
MCS (Multiple Circuit Summing-up) is a circuit method to improve various characteristics by connecting the same circuit in parallel. MCS + circuit is a further evolution of this circuit and realizes further noise reduction by extending the parallel operation part to A-class drive stage of current-voltage conversion part.
The current feedback amplifier circuit feeds back the output signal in the form of a current. Since the impedance of the feedback input part is extremely low, phase rotation hardly occurs, and various characteristics can be greatly improved with a small amount of NFB.
A power MOS-FET, which has a reputation for sound quality and reliability, is used as the output device. Each channel is driven by 6 parallel push-pull operation. The MOS-FET has negative thermal response to temperature rise, so that thermally stable operation can be obtained. This is a pure A-class system that brings out the charm of music.

A large-size high-efficiency toroidal transformer of up to 600 VA is adopted for the power supply section, and a large-capacity capacitor of 47,000 μ Fx2 is used for the smoothing capacitor.

Equipped with 4-stage gain control.
In this function, the gain is switched by the first stage amplifier of the instrumentation amplifier system, and residual noise is reduced.

A fully balanced input circuit is adopted, making it less susceptible to extraneous induction noise.

Main components of printed board copper foil and signal path are made into gold plates.

Equipped with an analog type large power meter.
Meter OFF function and sensitivity switching are also available.

The speaker terminal uses a large terminal that can be used with a Y lug or banana plug.

The A-45 is bridge-connected and can be used as a high-power monaural power amplifier.
Use the mode selector switch to switch between dual mono / stereo / bridge connections.

Model Rating

Type	Stereo power amplifier
Rated continuous average output (20 Hz to 20 kHz)	Stereo type (both channel operation) 360W + 360W (1 ohm load, music signal only) 180W + 180W (2 ohm load) 90W + 90W (4 ohm load) 45W + 45W (8 ohm load) Monaural specification (bridge connection) 720W (2 Ω load, music signal only) 360W (4 Ω load) 180W (8 Ω load)
Total harmonic distortion factor	Stereo type (both channel operation) 0.05% (2 Ω Load) 0.03% (4 Ω ~ 16 Ω Load) Monaural specification (bridge connection) 0.05% (4 Ω ~ 16 Ω Load)
IM distortion factor	0.004%
Frequency characteristic	20 Hz ~ 20 kHz + 0 -0.2 dB (at rated continuous average output) 0.5 Hz ~ 160 kHz + 0 -3.0 dB (at 1W Output)
Gain	28.0 dB (Gain switch at max) Both stereo and monaural specifications
Gain switching	Max, -3dB, -6dB, -12dB
Load impedance	Stereo specification : 2 Ω ~ 16 Ω Monaural specification : 4 Ω ~ 16 Ω * Only for music signals, stereo 1 Ω and monaural 2 Ω can be loaded
Damping factor	200
Input Sensitivity (8 Ω load, Gain switch : max)	Stereo specification 0.76 V (at rated continuous average output) Monaural specification 1.51 V (at rated continuous average output) 0.11 V (at 1W output)
Input impedance	Balance : 40k Ω Unbalanced : 20k Ω
S/N (A correction, input short)	115 dB (Gain Switch Max) 120 dB (gain switch -12dB) Rated continuous average output
Output meter	-50dB ~ ; 3 dB (dB /%) Logarithmic Compression Type, Display / Off Function, Meter Sensitivity Switching Function (-20dB)
Pwer	100 VAC, 50Hz/60Hz
Power consumption	235W (no input) 430W (Electrical Appliances and Materials Safety Act) 290W (at 8 Ω load rated output)
Maximum external dimensions	Width 465x Height 211x Depth 464 mm
Weight	30.9kg