Усилители мощности моно — Alexandria Audio Legatus

The Legatus is a hybrid monoblock power amplifier from Alexandria Audio of Bali, Indonesia, sold as a pair at USD 8,500. Alexandria Audio was founded in Bali in 2019 by Kenneth Lin and Henry Kristanto, who come from Bali and Jakarta, and the Legatus is the company's first amplifier and the result of two years of circuit development and about a year of preparation for production. It combines a valve buffer stage with a Hypex NCOREx Class D output module, and Alexandria has shown it with its Purva valve streamer and The Monitor loudspeakers.

Key specs that matter

Continuous output is 100 W into 8 ohm and 200 W into 4 and 2 ohm, with peak figures of 380 W into 8 ohm and 700 W into 4 and 2 ohm. The output module is a Hypex NcX500, rated at -130 dB distortion. The valve buffer uses 5687 double triodes. Inputs are balanced XLR and RCA, both presenting 100 kOhm and accepting up to 8 V. Frequency response is 2 Hz to 200 kHz. Output taps are labelled 4, 8 and 16. Each amplifier measures 480 x 165 x 380 mm and weighs 30.0 kg. Mains voltage is 115 or 230 V with a T5A slow-blow fuse, and consumption ranges from 40 W to 800 W.

Engineering and use context

The valve stage acts as a buffer in front of the Class D module, presenting a high input impedance to the preamplifier and driving the NcX500 input. A DIP switch lets the owner select a zero-feedback mode. Each monoblock has two independent power supplies, one for the valve stage and one for the output stage, so the high-voltage valve supply and the high-current Class D supply do not share components. The mono chassis gives each channel full separation of signal and ground. Capacitors and resistors are matched to tolerances between 0.1% and 0.001%. The chassis is compartmentalised steel with an aluminium faceplate, keeping the valve section, output module and supplies in separate spaces, and each unit is fine-tuned individually before shipping. Much of the weight comes from this steel construction and the two power supplies.

Pairing

Because its continuous rating holds steady into the lowest impedances, the Legatus copes with difficult loads, and the 16 ohm tap suits high-impedance speakers. Alexandria's Purva valve streamer can feed it directly, and the XLR input suits balanced preamplifiers.

Alternatives

Alexandria Audio makes no other power amplifier, its other electronics being the Nero preamplifier and the Purva valve streamer.