Cayin HA-300 MK3

Reference-Class 300B – Single-Ended Class A Tube Amplifier for Headphones and Loudspeakers

There are tube amplifiers – and then there is the 300B. For decades, this directly heated triode has enjoyed an almost legendary reputation among enthusiasts: not because of spectacular measurements or enormous output power, but because of its ability to give voices and instruments body, texture and an exceptionally natural sense of spatial presence.

The Cayin HA-300 MK3 is Cayin's most ambitious implementation of this principle for personal audio to date. As the third generation of its flagship 300B amplifier, it remains faithful to an uncompromising Single-Ended Class A topology, while its internal design has been extensively refined: new output transformers, a revised power supply, premium DUELUND coupling capacitors, new rectifier tubes and a substantially broader range of applications make the MK3 more capable and versatile than its predecessors.

The result is an amplifier that deliberately does not try to sound like a solid-state design. The HA-300 MK3 is not intended to dissect music into its individual components – it aims to reproduce it as a coherent whole, with colour, space, dynamics and the almost tangible physicality for which a superbly implemented 300B circuit is renowned.

The 300B – the Heart of the HA-300 MK3

The HA-300 MK3's output stage uses a matched pair of Genalex Gold Lion PX300B tubes. The 300B is a Direct Heated Triode (DHT), in which the filament itself forms part of the electron-emitting system. Its elegantly simple construction represents one of the most classic forms of tube amplification.

Much of its appeal lies precisely in that simplicity. A well-executed single-ended 300B circuit can render voices with exceptional dimensionality, preserve fine harmonic structures and create a sense of space and naturalness that is difficult to describe with technical terminology alone.

Cayin combines the two PX300B power tubes with JJ 6SN7 tubes for voltage amplification. The 6SN7 is itself one of the great classic dual triodes of audio design and provides an ideal foundation for a circuit focused on linearity, texture and musical coherence.

GZ34 / 5AR4 Tube Rectification

Cayin also remains faithful to tube technology in the power supply. The separate PSU chassis houses two JJ GZ34 / 5AR4 rectifier tubes.

Compared with the HA-300 MK2, which used 22DE4 rectifier tubes, the MK3 also opens up a considerably more interesting world of tube rolling. The GZ34 / 5AR4 is one of the most widely available high-quality rectifier tube families, giving owners access to a broad range of both current-production and vintage alternatives.

Together with the interchangeable 6SN7 and 300B tubes, this makes the HA-300 MK3 an amplifier whose sonic character can be tailored far beyond a simple change of source or headphones.

Third Generation – More Than a Cosmetic Update

The MK3 designation does not indicate a merely cosmetic revision. Cayin has comprehensively reworked the HA-300's circuitry and describes it as a new third-generation amplifier architecture.

Particular attention has been paid to components that are directly critical to the sound of a transformer-coupled single-ended amplifier.

• Third-generation wide-bandwidth output transformers
• Newly developed toroidal power transformer
• DUELUND coupling capacitors from Denmark
• Low-noise regulated voltage amplification stage
• Gold-plated tube sockets
• Traditional point-to-point hand wiring

In a single-ended tube amplifier, the output transformers form a fundamental part of the amplification circuit itself. Their role is not merely to match the high impedance of the 300B to a pair of headphones or loudspeakers: bandwidth, saturation behaviour and winding quality directly influence how cleanly dynamics, bass and fine signal detail are transmitted.

DUELUND in the Signal Path

For the coupling capacitors, Cayin uses components from Danish specialist DUELUND. These are the kind of parts typically found in high-end designs where the priority is no longer the cheapest or most compact component, but the quality of the signal path itself.

Together with the traditional point-to-point wiring, this underlines the philosophy behind the HA-300 MK3: it is not designed as an industrially optimised electronics platform, but as an elaborate analogue audio component in which the signal path takes centre stage.

Two Chassis – for Good Reason

The HA-300 MK3 separates its power supply and amplifier circuitry into two completely independent chassis.

For a sensitive single-ended tube amplifier, this is far more than a visual design choice. The mains transformer, rectification stage and high supply currents are physically separated from the audio circuitry, helping to keep magnetic and electrical interference away from the amplifier itself.

The substantial construction becomes immediately apparent on the scales: the amplifier itself weighs approximately 16.8 kg, while the separate power supply adds another 10 kg.

What Do Those Who Have Heard It Say?

With a 300B amplifier, technical specifications tell only part of the story. What matters just as much is whether all of this engineering ultimately delivers the spatial, physical and harmonically rich presentation that makes people choose a 300B amplifier in the first place.

“Dead quiet — even more so than the MK II.”
– ZMF Headphones on the Cayin HA-300 MK3

That is a particularly notable comment for such a powerful 300B amplifier. ZMF also highlights the MK3's characteristic 300B substance and harmonic richness, now combined with improved clarity and control.

“Classic 300B weight and euphonic harmonics, now with even better clarity and grip.”
– ZMF Headphones

A listening impression from CanJam London 2026 summarises the character of the amplifier just as succinctly:

“The sound is huge, it's extremely holographic and exceptionally dynamic.”
– Head-Fi, CanJam London 2026 Impressions

This combination is ultimately what the HA-300 MK3 aims to achieve: not warmth at any cost, but a large and three-dimensional presentation, natural tonal colour and the harmonic fluidity of a 300B, combined with sufficient control and dynamics for modern high-end headphones.

6.5 Watts – from a Single-Ended 300B Circuit

The HA-300 MK3 is by no means intended only for high-impedance dynamic headphones. Cayin has designed the output stage with enough reserves to drive demanding planar magnetic models as well.

The 4-pin XLR output delivers up to 6,500 mW + 6,500 mW, while the traditional 6.35 mm output provides up to 6,000 mW + 6,000 mW.

This allows Cayin to combine the sonic qualities of a traditional single-ended triode circuit with an output level far beyond what one might initially associate with a classic 300B amplifier.

From IEMs to Large Planar Headphones

One of the most important practical developments of the MK3 concerns particularly sensitive headphones.

The balanced 4.4 mm Pentaconn output has been optimised specifically for lower power requirements and more sensitive transducers. It provides 1,600 mW + 1,600 mW.

In addition, the output transformer can be matched to different headphones via three selectable impedance ranges:

• Low: 8–65 Ω
• Medium: 65–300 Ω
• High: 300–600 Ω

This gives the HA-300 MK3 an unusually broad operating range: from sensitive in-ear monitors and low-impedance dynamic or planar magnetic headphones to classic high-impedance models.

Precise Volume Control

With an amplifier intended to drive both sensitive headphones and demanding flagship models, precise volume control is essential.

Cayin therefore uses a JRC MUSES 72320V in combination with a 41-step ALPS attenuator. This allows fine and controlled volume adjustment while retaining remote-control functionality.

A 60-second soft-start sequence allows the tubes to reach operating temperature in a controlled manner before the amplifier activates its outputs.

Not Just a Headphone Amplifier: 8 Watts for Loudspeakers

The rear panel reveals another detail that shows how seriously Cayin takes the description “Headphone / Speaker Amplifier”: the HA-300 MK3 includes dedicated loudspeaker outputs.

Suitable loudspeakers can be driven with 8 watts + 8 watts in Class A. On paper, that may initially appear modest – but with efficient loudspeakers, eight high-quality single-ended 300B watts can be more than sufficient.

The HA-300 MK3 can therefore serve equally well as the centrepiece of an uncompromising headphone system or of a compact high-end setup built around efficient loudspeakers.

Purely Analogue by Design

You will deliberately find no digital inputs, DAC, streaming functions or DSP in the HA-300 MK3. Cayin focuses entirely on one task: amplifying an analogue input signal to the highest possible standard.

Both RCA and XLR inputs are provided. On the output side, the HA-300 MK3 offers:

• 1 × 4-pin XLR headphone output
• 1 × 4.4 mm Pentaconn headphone output
• 1 × 6.35 mm headphone output
• 1 × loudspeaker output for 4–8 Ω loads

Cayin HA-300 MK3 – Highlights

• Flagship tube amplifier for headphones and loudspeakers
• Pure Single-Ended Class A circuit
• 2 × Genalex Gold Lion PX300B power tubes
• 2 × JJ 6SN7 voltage amplification tubes
• 2 × JJ GZ34 / 5AR4 rectifier tubes
• New third-generation circuit architecture
• Third-generation wide-bandwidth EI output transformers
• Newly developed toroidal power transformer
• DUELUND coupling capacitors
• Point-to-point hand wiring
• Separate power supply chassis
• Up to 6.5 W + 6.5 W via 4-pin XLR
• IEM-optimised 4.4 mm Pentaconn output
• Three selectable headphone impedance ranges
• 8 W + 8 W loudspeaker output
• JRC MUSES 72320V volume control with 41-step ALPS attenuator
• 60-second start-up delay
• Remote control included

Technical Specifications