Transformer-coupled Class A headphone amp

The Cayin HA-2A is a transformer-coupled, single-ended Class A headphone amplifier built around vintage NOS vacuum tubes and wide-bandwidth EI transformers. It gives you three headphone outputs—6.35mm single-ended, 4.4mm balanced, and 4-pin XLR balanced—plus impedance matching (Low/Mid/High) so you can dial in the output for your headphones. On the back, you get both XLR and RCA analog inputs for pairing with your DAC, CD player, streamer, or any line-level source.

Vintage NOS tube circuit

The HA-2A uses five vintage NOS tubes chosen for specific roles in the circuit: two Amperex 17BF11 for single-ended Class A power amplification, two Amperex ECF82/6U8 for voltage amplification, and one RCA 17AX4GT rectifier for the preamp-stage plate supply. 

Transformer-coupled output stage

This is a transformer-coupled tube amp, which means the output transformer is doing the hard work of matching the tube stage to the headphone load. Cayin builds the wide-bandwidth EI output transformers for this model in-house, using a Z11 EI iron core and a hand-winding process, then encloses and resin-seals the transformers to reduce interference and keep performance consistent.

Impedance matching for better control

The impedance selector lets the amplifier optimize output behavior for different headphone impedance ranges—Low (8–64Ω), Mid (65–250Ω), and High (251–600Ω). This helps the amp maintain control and keep bass definition steady as you move between different headphones. 

60-second start-up delay

There’s a built-in 60-second start-up delay circuit to protect the amplification stage, reduce pop noise at power-on, and let the tubes warm to a stable operating condition before playback. 

Tube protection and microphonics control

A tube protection cage keeps hands away from hot glass while also helping reduce interference around the tube area. The reinforced chassis base is designed to minimize microphonic ringing from impact and vibration.

Point-to-point wiring

The internal circuit is point-to-point wired with hand-soldered routing intended to keep signal paths short and reduce interference. This helps with long-term reliability and consistency, especially in tube designs where layout and grounding choices can shape noise performance.

Compact footprint with clear controls

Despite the transformer-coupled design and tube complement, the HA-2A keeps a desktop-friendly size: about 10.6 × 8.5 × 5.6 in (270 × 215 × 143 mm) and 22.0 lb (10 kg). Up front, you get a dedicated source selector, a backlit dual VU meter display, a volume control with indicator, and a headphone output selector so the basic controls stay where your hand already is.

Product highlights

• Transformer-coupled, single-ended Class A headphone amplifier
  
• Vintage NOS tube set: Amperex 17BF11 ×2, Amperex ECF82/6U8 ×2, RCA 17AX4GT ×1
  
• Headphone outputs: 6.35mm single-ended, 4.4mm balanced, 4-pin XLR balanced
  
• Headphone impedance selector: Low / Mid / High
  
• 60-second start-up delay circuit to reduce pop noise and protect the circuit
  
• Wide-bandwidth EI transformers with Z11 EI core and resin-sealed metal casing
  
• Point-to-point wiring
  
• Frequency response: 20Hz–50kHz (±3dB)
  
• THD+N: 0.2% (1kHz, 100mW)
  
• SNR: 100dB (A-weighted)

Specs

• Analog inputs: XLR ×2, RCA ×2
  
• Headphone connectors: 4-pin XLR ×1, 4.4mm ×1, 6.35mm ×1
  
• Headphone impedance ranges: Low 8–64Ω, Mid 65–250Ω, High 251–600Ω
  
• Rated output (per channel): 4-pin XLR (BAL) 800mW (L) / 900mW (M) / 1000mW (H)
  
• Rated output (per channel): 4.4mm (BAL) 200mW (L) / 300mW (M) / 270mW (H)
  
• Rated output (per channel): 6.35mm (SE) 330mW (L) / 550mW (M) / 750mW (H)
  
• Frequency range: 20Hz–50kHz (±3dB)
  
• THD+N: 0.2% (1kHz, 100mW)
  
• SNR: 100dB (A-weighted)
  
• Power consumption: 60W
  
• Dimensions: 10.6 × 8.5 × 5.6 in (270 × 215 × 143 mm)
  
• Weight: 22.0 lb (10 kg)
  
• Working conditions: 32°F–104°F (0°C–40°C), humidity 20%–80%
  
• Storage conditions: −4°F–158°F (−20°C–70°C), humidity 20%–90%
  
• Fuse (220–240V): T500mAL250V
  
• Fuse (100–120V): T1AL250V
  
• Output tube fuse: T125mAE250V

What’s included

• HA-2A headphone amplifier
  
• Vacuum tube protection cage
  
• Vacuum tubes: Amperex 17BF11 ×2, Amperex ECF82/6U8 ×2, RCA 17AX4GT ×1
  
• AC power cord