Усилители мощности стерео — Pearl Acoustics 170 SE

The 170 SE is a single-ended valve stereo power amplifier from Pearl Acoustics, the company founded by Harley Lovegrove, a British-born maker living in Belgium, who began with the Model One single-driver loudspeaker, earlier called the Sibelius. The 170 was designed first of all to drive those speakers but also any other make. The SE version brought a revised layout, a simpler architecture, upgraded parts and a modified chassis finished by a UK case builder, with custom colours possible, and manufacturing moved in-house in Belgium. The company also makes the 7040 Class D power amplifier.

Key specs that matter

A single power valve per channel works in single-ended Class A. With KT170 valves the output is 18 W into 8 ohm, and with KT150 valves 16 W, and the SE is supplied with PSVANE Horizon KT150 valves. Input sensitivity is 1 V RMS for full power into 8 ohm, input impedance is 10 kohm and gain is 21.6 dB. Frequency response covers 20 Hz to 20 kHz, and distortion at 1 W into 8 ohm is 0.5 percent second harmonic and 0.03 percent third harmonic. The damping factor is 6. The amplifier measures 405 mm wide, 235 mm high and 375 mm deep and weighs 31 kg unpacked, and it draws 250 W in use and at most 0.9 W in standby.

Engineering and use context

The design is dual mono, with a separate circuit for each channel, and it uses no global feedback of any kind. There are no solid-state devices, followers or buffers in the signal path, which is kept very short. Pearl describes it as a high-current, low-impedance design that stays stable down to 2 ohm. The output transformers and power supply are custom designed and made for the amplifier, and the valve sockets are mounted on the chassis. Bias is set by a self-regulating cathode bias circuit, so the owner does not adjust it when changing valves. A sequenced soft start brings the amplifier up in stages, and a protection circuit guards the power valves and the electronics. KT150 and KT170 valves can be swapped, and other valve types are sold through the company's webshop.

Pairing

The low damping factor and modest power suit high-sensitivity loudspeakers, such as single-driver designs like Pearl's own Model One. The standard input sensitivity lets a valve or solid-state preamplifier, or a source with variable output, drive it to full power.

Alternatives

The Pearl Acoustics 7040 is a dual mono Class D stereo power amplifier on Purifi modules rated at 250 W per channel into 8 ohm.