Интегральные усилители — Pathos Acoustics InPoL Legacy

The InPoL Legacy is the reference stereo integrated amplifier of Pathos Acoustics, the Italian company that developed the InPoL output circuit. It was created as a tribute to co-founder Gaetano Zanini and marks more than 25 years of the firm's work, following an earlier tribute model in the InPoL line. Zanini has said the team placed no limits on weight or size for this project, and the result is a hybrid valve and transistor design in pure class A.

Key specs that matter

Output is 100 W per channel into 8 ohm and 170 W into 4 ohm. The response runs from 2 Hz to 100 kHz within 0.5 dB, distortion is 0.02 percent at 1 W and 0.5 percent at 100 W, both at 1 kHz, while noise sits more than 97 dB below signal. Gain is 31 dB through the single-ended inputs and 25 dB through the balanced ones, input sensitivity is 700 mV RMS and the maximum input voltage is 10 V RMS. Three XLR and three RCA line inputs use Neutrik and WBT hardware. The chassis is 500 mm wide, 880 mm deep and 300 mm high.

Engineering and use context

InPoL stands for Inseguitore Pompa Lineare, or linear pump follower, a patented circuit that takes care of current gain without phase shift while a single triode stage does all the voltage amplification. Pathos states that InPoL raises the theoretical efficiency of pure class A from 25 to 50 percent. Here two InPoL stages run in a fully balanced bridged configuration, arranged as a dual-mono layout, and class A bias avoids crossover distortion. The valve section uses four Tung-Sol ECC803 and two Sovtek 6H30 tubes in a totem pole arrangement. Two toroidal mains transformers, the largest Pathos has ever made, feed the output stages, while the valve stage of every channel draws on a separate toroidal unit and a capacitive-inductive filter. Level is set by a 100-step passive attenuator of low-noise precision resistors switched by insulated relays. Capacitors come from Itelcond and ICEL and resistors from Vishay.

Pairing

The amplifier weighs 140 kg, so Pathos ships it in special packaging with wheels and supplies lifting brackets, and a dedicated support cabinet is available for it. Since its output rises into a lower load, the Legacy can drive lower-impedance speakers as well as 8 ohm models, and the six line inputs leave room for balanced and single-ended sources side by side. The separate gain figures for XLR and RCA should be kept in mind when switching between inputs, since a balanced source reaches the same volume at a different attenuator step.

Alternatives

The Pathos InPoL Heritage MkII is the earlier tribute integrated in the same InPoL range, dedicated to Gianni Borinato.