Усилители мощности стерео — Parasound HALO A52+

The Parasound HALO A52+ belongs to the Halo series as a five-channel power amplifier, engineered by John Curl and built into a 3U chassis. Parasound states that it fits both stereo and surround systems thanks to flexible connections and automatic power detection. It is priced at USD 4,000, and Parasound covers parts and labor for three years. Shipping weight is 31.3 kg.

Key specs that matter

Rated across five loaded channels, output is 180 W per channel into 8 ohms and 255 W into 4 ohms. If just two channels are working, it produces 225 W into 8 ohms and 350 W into 4 ohms. Peak current capacity is 45 A per channel. THD is below 0.05% at full power and below 0.03% at typical listening levels. Intermodulation distortion stays under 0.04%, and transient IM cannot be measured. Noise performance is better than 112 dB IHF A-weighted and 102 dB unweighted. Frequency response is 5 Hz to 100 kHz at plus 0 and minus 3 dB, and 20 Hz to 20 kHz within 0.3 dB, with full power rated down to 5 Hz. Damping factor is above 1100 at 20 Hz, slew rate above 130 V per microsecond and dynamic headroom above 1.5 dB. Crosstalk exceeds 78 dB at 1 kHz and 63 dB at 20 kHz.

Engineering and use context

Circuitry is high-bias Class A/AB with a direct-coupled signal path, and the input and driver stage transistors are matched by hand. A custom 1.5 kVA toroidal transformer feeds each channel from its own secondary, and filter capacitance totals 100,000 uF. Protective duties fall to DC servo and relay circuits. Input sensitivity is 1 V for 28.28 V at the output on both balanced and unbalanced inputs, total gain is 29 dB, and input impedance is 47 kilohm unbalanced or 94 kilohm balanced, 47 kilohm per leg. The case is 437 mm wide, 133 mm tall without feet or 149 mm with them, and 508 mm deep, growing to 540 mm with cables attached. Net weight is 25 kg. Power draw is 1 W in standby, 125 W at idle and up to 1,500 W. Rack mounting needs the HRA3 bracket, sold separately.

Pairing

Five XLR and five RCA sockets serve as inputs, one of each per channel, and the unit can switch on through a 12 V trigger or by sensing an audio signal, so it follows a surround processor or a stereo preamplifier without a separate power step. Gold-plated 5-way binding posts take speaker wire, and Parasound notes that the model suits stereo as well as surround setups.

Alternatives

The Parasound HALO A51 offers five channels in a 4U chassis rated at 250 W per channel into 8 ohms with all channels driven.