Headphones amplifiers — Erzetich Audio Perfidus

The Perfidus is a solid-state Class A headphone amplifier made by Erzetich Audio, a company founded in Slovenia in 2012 that builds both headphones and the electronics to drive them. It sits in the Erzetich amplifier range alongside the Bacillus, Deimos and Scylla, and it was priced at USD 1,099 and GBP 999. The case has a grey matte finish.

Key specs that matter

Erzetich rates the Perfidus for headphones from 8 to 600 ohm, which covers everything from low-impedance planar designs to high-impedance dynamic studio models. The frequency response is quoted as 4 Hz to 40 kHz at -1 dB, total harmonic distortion as 0.007% at 1 kHz and intermodulation distortion as 0.077%. Power consumption is 15 W, and each unit is wired for either 230 V at 50 Hz or 115 V at 60 Hz depending on the market it is sold in. The chassis measures 110 mm wide, 64 mm high and 285 mm deep and weighs 1,480 g.

Engineering and use context

At the input end an OPA627 op-amp works with WIMA pulse capacitors at the input and no capacitors in the output path. It drives a push-pull current buffer built from STMicroelectronics BD139 and BD140 bipolar transistors, set up with a gain just above 1, and a further op-amp detects and corrects DC offset at the output. The four main transistors are bolted to the side of the case, which doubles as the heatsink. An ALPS Blue Velvet potentiometer, turned through a solid aluminium knob, controls the level. Power comes from a toroidal transformer feeding an on-board stabilised supply of 2 x 15 V, backed by four Rubycon capacitors totalling 40,000 uF. Early units had a fixed mains cord, and later production moved to an IEC inlet. The unusual depth of the case is deliberate, since the supply sits at the rear and the amplification section at the front, keeping the transformer away from the low-level circuitry to limit noise. A 7 mm thick aluminium front panel carries the knob, the single headphone jack and a status LED, while the rear holds a pair of gold-plated RCA inputs and the mains switch. The narrow footprint lets the Perfidus stand beside a DAC or streamer on a crowded desk.

Pairing

With one line-level RCA input and no built-in conversion, the Perfidus needs an external DAC or a source with analogue outputs. Its wide load range suits the Erzetich Charybdis and Phobos planar headphones and high-impedance dynamic headphones from other makers, and users switching between several pairs can keep one amplifier for all of them.

Alternatives

The Erzetich Deimos is a Class A headphone amplifier in dual-mono layout that uses relay-based volume control instead of a potentiometer.