Acoustic Research A-03
The Acoustic Research A-03 is a high-fidelity stereo amplifier designed for clean and detailed sound reproduction. It features a dual-mono power supply with two transformers and eight 2200µF filter capacitors. The output stage uses 2SD1047 and 2SB817 transistors and does not include a speaker protection relay. Only one pair of speakers is supported.
The front panel is minimalistic, with most controls hidden behind a flip-down door. There are no tone controls, and a CD Direct option is included for a shorter signal path.
Built with Acoustic Research's focus on a simple signal path, the A-03 offers a warm sonic character, making it suitable for both vintage and modern speaker setups.
Manufacturer: Acoustic Research
Status: Defunct company
Source: Wikipedia (Acoustic Research)
General Specifications
Maximum power (8Ω): 30WMaximum power (4Ω): 40W
Frequency response (15Hz-20kHz): 0,-0.3dB
THD+N: 0.07%
IMD: 0.005%
Signal to noise ratio (Line): 96dB
Signal to noise ratio (MM): 80dB
Crosstalk: 75dB
Damping factor: 120
Speaker load impedance: 4Ω-16Ω
Dimensions (WHD): 430×93×354mm
Weight: 6.6kg
Produced: 1991
Initial price: 140GBP
Measured Values
Maximum power (8Ω): 40WFrequency response (20Hz-20kHz): <0.2dB
Channel imbalance: <1.0dB
THD (1kHz, 1W): 0.02%
THD+N (1kHz, 1W): 0.03%
THD (1kHz, 20W): 0.028%
THD+N (1kHz, 20W): 0.028%
IMD (70Hz, 5kHz, 1W): 0.064%
Noise: -67.9dB
Amplification (Line): 96.7
DC offset L: 27mV
DC offset R: 60mV
Factory Specification Sheet
Factory specification images are sourced directly from the device's original service manual or user manual. These documents are produced by the manufacturer and provide authoritative information on the product's specifications.
Maximum Power
Maximum power is measured using 8Ω resistors on both channels. A 1kHz sine wave input signal is applied and gradually increased until higher harmonics rise significantly. Typically, this is the point at which output clipping occurs.
Frequency Response
Frequency response is measured using several equilizer settings. 'Flat' indicates the tone controls are either turned off or set to their neutral position. 'Max' and 'Min' refer to the maximum and minimum tone control positions, respectively. In the phono section, the expected response follows the RIAA equalization curve.
Residual Noise
These graphs display the noise levels at various volume positions. To eliminate any interference from the input signal, the input lines are shorted during the measurement. Generally, the noise is highest at the mid-point of the volume range (50%)
Distorsion
Total harmonic distortion (THD) is measured using a 1kHz sine wave input, with the output level adjusted to meet different conditions. Intermodulation distortion (IMD) is measured using 'two sine' input signal. THD versus voltage is measured with a 1kHz sine wave input, while THD versus frequency is measured at various output levels.
Known Problems
In this particular unit, the right channel performs slightly worse than the left, which may be due to a failed component or a dirty contact in the selector switch.