Class-A 12AU7 headphone amp and preamp

The Cayin HA-1A MK3 is a compact Class-A tube headphone amplifier and preamplifier built around 12AU7/ECC82 and EL84/6BQ5-family vacuum tubes. Dedicated power and output transformers support its fully analog signal path, while selectable headphone impedance matching and 6.35 mm or 4-pin XLR outputs provide flexibility across a wide range of headphones.

Pure tube amplification

The HA-1A MK3 uses two JJ 12AU7/ECC82 tubes alongside two Electro-Harmonix EL84EH/6BQ5 tubes. Its vacuum-tube circuit is designed around the tonal density, smooth character, and expressive presentation associated with Cayin’s dedicated tube amplifiers.

Class A operation

Class-A amplification keeps the output stage operating continuously through the signal cycle, prioritizing linear operation over maximum efficiency. Cayin has tuned the HA-1A MK3 for detail, dynamics, tonal weight, and comfortable extended listening across a broad range of music.

Purpose-designed transformers

Cayin developed dedicated power and output transformers specifically for the HA-1A MK3 circuit. Separate power-supply sections and a carefully arranged internal layout provide a stable electrical foundation while helping reduce unwanted interference within the amplifier.

Flexible headphone matching

A two-position impedance selector accommodates headphones with different electrical requirements. The Low setting supports 8–150 ohms, while the High setting covers 151–600 ohms. This allows the amplifier to work with low-impedance planar magnetic headphones as well as higher-impedance dynamic designs.

Balanced and single-ended outputs

The front panel provides a 6.35 mm single-ended headphone output rated at 2,400 mW + 2,400 mW and a 4-pin XLR balanced output rated at 2,700 mW + 2,700 mW. Both connections give users practical flexibility when pairing the amplifier with different headphone cables and terminations.

Dedicated preamplifier output

A rear-panel RCA PRE-OUT allows the HA-1A MK3 to serve as a tube preamplifier for active loudspeakers or an external power amplifier. With two pairs of RCA inputs, the amplifier can sit at the center of a compact desktop audio system while handling both headphone and speaker-based listening.

Selected internal components

An ALPS volume potentiometer joins the custom transformers and dedicated power-supply sections inside the chassis. Cayin combines these components with hand assembly and inspection as part of its established tube-amplifier manufacturing approach.

Product highlights

• Class-A vacuum-tube headphone amplifier
  
• Two JJ 12AU7/ECC82 tubes
  
• Two Electro-Harmonix EL84EH/6BQ5 tubes
  
• Dedicated power and output transformers
  
• Low and High headphone impedance matching
  
• 6.35 mm single-ended headphone output
  
• 4-pin XLR balanced headphone output
  
• Up to 2,700 mW + 2,700 mW rated balanced output power
  
• RCA preamplifier output
  
• Two pairs of RCA audio inputs
  
• ALPS volume potentiometer
  
• Compact desktop chassis
  

Specs

• Amplification topology: Class A vacuum tube
  
• Rated output power, 6.35 mm: 2,400 mW + 2,400 mW
  
• Rated output power, 4-pin XLR: 2,700 mW + 2,700 mW
  
• Frequency response: 20 Hz–20 kHz, -3 dB
  
• Headphone output THD: 0.3% at 1 kHz and 200 mW, less than 5% at rated output power
  
• Headphone output sensitivity: 1,200–2,000 mV
  
• Headphone output SNR: 110 dB A-weighted
  
• Headphone impedance setting, Low: 8–150 ohms
  
• Headphone impedance setting, High: 151–600 ohms
  
• Headphone outputs: 6.35 mm single-ended and 4-pin XLR balanced
  
• Preamplifier maximum output voltage: 5 V
  
• Preamplifier gain: 9 dB
  
• Preamplifier THD: 0.1% at 2 V RMS
  
• Preamplifier SNR: 105 dB A-weighted
  
• Preamplifier input sensitivity: 750 mV
  
• Preamplifier output impedance: 1.5 kohms
  
• Preamplifier output: 1 pair RCA
  
• Input impedance: 23 kohms
  
• Audio inputs: 2 pairs RCA
  
• Vacuum tubes: JJ 12AU7/ECC82 ×2 and Electro-Harmonix EL84EH/6BQ5 ×2
  
• Dimensions, W × D × H: 9.45 × 9.45 × 5.51 in (240 × 240 × 140 mm)
  
• Net weight: 19.4 lb (8.8 kg)
  
• Fuse, AC 220–240 V: T500mAL250V
  
• Fuse, AC 100–120 V: T1AL250V
  
• Maximum power consumption: 62 W

What’s included

• Cayin HA-1A MK3 tube headphone amplifier
  
• JJ 12AU7/ECC82 vacuum tubes ×2
  
• Electro-Harmonix EL84EH/6BQ5 vacuum tubes ×2
  
• Additional package contents were not specified in the provided launch materials