Headphones amplifiers — Allnic Audio HPA-10000

The Allnic Audio HPA-10000 OTL/OCL is a valve headphone amplifier that doubles as a line-stage preamplifier. It arrived at the start of 2024 priced at USD 15,000 in the US, later lowered to USD 13,200, and sells in Europe for about EUR 16,400. Silver and black finishes exist. The model follows the HPA-5000, the first commercially produced OTL/OCL unit by Allnic founder Kang Su Park, and its circuit was carried over into the HPA-15,000 OTL/OCL Signature. Allnic plans to discontinue the HPA-10000 during 2026 after a final production run.

Key specs that matter

Operating in pure Class A, the amplifier delivers 10 W continuously into 50 ohm. Allnic recommends headphones between 15 and 600 ohm and quotes a voltage gain of +28 dB with a flat response from 20 Hz to 20 kHz. The input selector covers five sources - three on RCA and two on XLR. Listeners plug in through two 6.3 mm jacks and two four-pin balanced XLR sockets, and an RCA pair at the back works as the preamplifier output with +16 dB of gain and a 20 ohm output impedance.

Engineering and use context

In this OTL/OCL design the valves reach the load without any output transformer or output capacitor in between. Allnic explains that these coupling devices normally keep the DC operating voltage away from the headphones or the following amplifier, and that removing them takes their influence and added distortion out of the signal path. To make this work, the circuit pairs negative and positive feedback in a cancellation arrangement, which the maker calls critical to OTL/OCL operation. The volume control is the same precision 61-step constant impedance attenuator with single silver contacts used in the top Allnic line-stage preamplifiers, so the impedance stays fixed and the two channels stay matched at every step. The first-stage valves sit in liquid rubber damper sockets against vibration, and the amplifier is designed for New Old Stock valves. Construction and materials comply with the EU RoHS rules.

Pairing

All five outputs can work at once, though Allnic advises against it. Used as a preamplifier, its unbalanced line stage has an output impedance low enough to match any power amplifier. The maker describes it as an ideal partner for high-efficiency dynamic headphones, and the 10 W reserve also covers low-efficiency planar models such as the HiFiMan Susvara. Volume and input changes are made from the remote control.

Alternatives

The Allnic Audio HPA-300B is a transformer-coupled valve headphone amplifier that also drives loudspeakers.