Cayin HA-300 MK3

Third generation of Cayin’s flagship headphone product, the HA-300 MK3 reprises the single-ended (SET) topology in pure class A around directly heated 300B triodes, a formula the Chinese brand has been refining for nearly a decade. Revised circuit, new-generation transformers, redesigned power supply, and expanded compatibility with sensitive IEMs: this iteration does not change the philosophy, it takes it further.

Two chassis, one isolation principle

The HA-300 MK3 physically separates the amplifier and its power supply into two distinct enclosures. The idea is simple: keep the power transformers and their magnetic field away from the audio path to limit interference, vibrations, and residual noise. The two units communicate via an umbilical cable with a lockable aviation-type connector, which secures the connection and reduces losses. The terminals are protected against dust when the cable is disconnected. This design choice already existed on the MK2, but Cayin announces specific work on EMI isolation and on the mechanical rigidity of the chassis, which helps lower the noise floor.

The whole unit is heavyweight: 16.8 kg for the amplifier (286 × 368 × 205 mm) and 10 kg for the power supply block (159 × 345 × 205 mm). This is a desktop device, designed to stay in place.

Transformers designed and wound in-house

Transformers are a critical element in a transformer-coupled SET amplifier: they directly shape tonal density, soundstage, and transient behavior. Cayin designs and winds its own in-house, a know-how that few manufacturers still master today. The MK3 introduces a third generation of wide-band EI output transformers and toroidal power transformer, both optimized for this platform.

Compared with previous versions, Cayin claims reinforced shielding, lower residual ripple, reduced interference, and a more stable power supply. The wide bandwidth of these transformers promotes consistent reproduction across the entire spectrum. The result obviously depends on the rest of the chain, but mastery of the output transformer is a structural advantage in this topology: it is what “speaks” to the headphones.

Six tubes, a minimalist circuit

The SET philosophy is based on the simplicity of the signal path. A single power tube per channel (the 300B) amplifies the signal without splitting it, which preserves the even-order harmonics prized in high-fidelity listening. The voltage stage uses a pair of 6SN7s, a classic duo with the 300B, while rectification is handled by two GZ34 / 5AR4 tubes.

The MK3 comes with a selected set of tubes: two Genalex Gold Lion PX300B tubes in output, two JJ 6SN7 tubes in the driver stage, and two JJ GZ34 tubes for rectification. Each tube is tested, matched, and subjected to 48 hours of burn-in at the factory before shipping. The switch to GZ34 tubes (the MK2 used four 22DE4 NOS RCA tubes) opens up a wider field of replacement options for “tube rolling,” a common practice in the world of tube amplifiers to tailor the sound signature to one’s tastes.

All internal wiring is point-to-point, done by hand.

Three headphone outputs, three impedance ranges

One of the frequent criticisms aimed at 300B amplifiers for headphone listening is their difficulty with sensitive IEMs: too much background noise, too much available power, not enough finesse in volume control. The MK3 tackles this problem with three distinct outputs, each calibrated for a different use.

The balanced Neutrik 4-pin XLR output delivers up to 6,500 mW per channel. This is the main output, designed for planar magnetic headphones and high-impedance models that demand current. The 6.35 mm jack output provides 6,000 mW per channel in single-ended mode. The 4.4 mm Pentaconn output, capped at 1,600 mW per channel, is specifically optimized for IEMs: suitable level, reduced noise. This is rare on a 300B amplifier, and it is one of the significant new features of this generation.

A three-position impedance selector (Low: 8-65 Ω, Medium: 65-300 Ω, High: 300-600 Ω) makes it possible to adapt the output load to the headphones used. Frequency response extends from 12 Hz to 35 kHz (±3 dB), signal-to-noise ratio is rated at 100 dB (A), and total harmonic distortion remains below 1% at 1 kHz.

An amplifier for speakers, too

The HA-300 MK3 is not just a headphone amplifier. Its rear binding posts deliver 2 × 8 W in class A, with a frequency response of 10 Hz to 35 kHz and a signal-to-noise ratio of 102 dB (A). This is low in absolute terms, but sufficient to power compact speakers with good sensitivity in an office or a modest-sized room. Accepted impedance ranges from 4 to 8 Ω. For those who alternate between headphone listening and speaker listening, the dual use avoids multiplying devices.

Selected components and hybrid volume control

The choice of passive components says a lot about the MK3’s positioning. The coupling capacitors are DUELUND units, made in Denmark, known in the tube amplification world for their low distortion and transparency. The tube sockets are gold-plated (and no longer ceramic with gold-plated pins as on previous generations), which improves conductivity, contact stability, and durability.

Volume adjustment combines two technologies: a JRC MUSES 72320 chip (high-fidelity electronic control, with low noise and low distortion) associated with a 41-step ALPS attenuator. This hybrid solution aims for the precision of digital adjustment with the smoothness of a stepped potentiometer.

A design revised down to the details

Compared with the MK2, the finish evolves toward a sandblasted treatment that resists scratches and fingerprints better than a classic brushed finish. The transformer cover has been streamlined: the decorative aluminum plates disappear in favor of a more understated design that promotes heat dissipation. The tube protection cage adopts a new “family” design with a plug-in structure, replacing the old wire mesh grille. Installation and replacement of the tubes are thereby made easier. The nameplate adopts a textured relief and the tube rings have been reworked. Two VU meters on the front panel add a visual reference during listening. A 60-second delay with mute at power-on protects the circuit and the headphones while the tubes reach their operating state.

On the input side, the MK3 accepts one balanced XLR source and one RCA source, with input impedances of 12.5 kΩ (XLR) and 25 kΩ (RCA). There is no line output: this is a pure amplifier, not a preamplifier. There is also no remote control, which means you need to get up to adjust the volume when listening through speakers.

Technical specifications

Architecture and design

• Topology: single-ended class A with 300B triodes
• Design: dual chassis with separate power supply
• Wiring: hand-wired point-to-point
• Power stage: 300B
• Voltage stage: regulated low-noise
• Power supply: enhanced circuit with better isolation and reduced interference
  • Secure aviation-type connector

Audiophile components

• Wideband EI output transformers (3rd generation)
• Toroidal power transformer (3rd generation)
• DUELUND coupling capacitors (Denmark)
• Volume control
  • JRC MUSES 72320 chip
  • ALPS 41-step attenuator
• Gold-plated tube sockets
• Selection of matched tubes with 48-hour factory burn-in

Included tubes

• 2 × Genalex Gold Lion PX300B
• 2 × JJ 6SN7
• 2 × JJ GZ34 / 5AR4
• Compatible with many equivalent tubes for sound customization (tube rolling)

Headphone output

• Power
  • Balanced 4-pin XLR: 6500 mW + 6500 mW
  • 6.35 mm jack: 6000 mW + 6000 mW
  • Balanced 4.4 mm: 1600 mW + 1600 mW (IEM optimized)
• Frequency response: 12 Hz – 35 kHz (±3 dB)
• Total harmonic distortion: less than 1% (1 kHz)
• Signal-to-noise ratio: 100 dB (A)
• Sensitivity: 250 mV – 1200 mV
• Impedance ranges
  • Low: 8 – 65 Ω
  • Medium: 65 – 300 Ω
  • High: 300 – 600 Ω
• Connectivity
  • 1 × 4-pin XLR
  • 1 × 6.35 mm jack
  • 1 × balanced 4.4 mm

Speaker output

• Power: 8 W + 8 W
• Frequency response: 10 Hz – 35 kHz (±3 dB)
• Total harmonic distortion: less than 1% (1 kHz, 3 W)
• Signal-to-noise ratio: 102 dB (A)
• Impedance: 4 – 8 Ω

Connectivity

• 1 × balanced XLR input
• 1 × RCA input
• 1 × speaker output (binding posts)
• Headphone impedance selector: High / Medium / Low

Design and manufacturing

• Sleek, modern industrial design
• Premium sandblasted finish
• Redesigned tube protection cage
• Premium details: textured nameplate, improved tube rings
• Dual front-panel VU meters

Dimensions and weight

• Amplifier: 286 × 368 × 205 mm – 16.8 kg
• Power supply: 159 × 345 × 205 mm – 10 kg

Power supply

• Consumption: 160 W maximum
• Voltage
  • 220 – 240 V: T1.6A L250V fuse
  • 100 – 120 V: T3.15A L250V fuse
• 300B fuse: T100 mA E250V

Operating conditions

• Temperature: 0 °C to 40 °C
• Humidity: 20% to 80%

General information

The Cayin HA-300 MK3 retains the iconic pure single-ended class A 300B triode architecture, the brand’s sonic signature, while incorporating a complete third-generation evolution. Redesigned circuit, optimized power supply, improved transformers, and a selection of audiophile components: every element has been revised to deliver more refined, more stable, and quieter reproduction. More versatile than ever, the HA-300 MK3 is equally suited to sensitive IEMs and high-end high-impedance headphones, while preserving the rich, natural musicality characteristic of 300B tube amplifiers.