Transformer-coupled tube headphone amplifier

The Cayin HA-3A is a desktop vacuum tube headphone amplifier built around a transformer-coupled, balanced-driven architecture. It uses a single-ended tube circuit with carefully matched tubes and custom output transformers to support both balanced and single-ended headphones. With impedance-matched outputs, multiple headphone connections, and a compact A4-sized footprint, the HA-3A is designed for listeners who want tube sound with practical flexibility for daily listening at a desk or dedicated listening space.

Single-ended tube amplification

The HA-3A is designed as a two-stage single-ended vacuum tube circuit. A matched pair of 12AU7 / ECC82 driver tubes amplifies the incoming signal voltage before handing it off to matched 6V6S output tubes. This approach preserves harmonic richness and linearity without signal cancellation, allowing the tonal character of the tubes to remain intact while maintaining controlled, predictable output.

Transformer-coupled balanced drive

Instead of relying on a fully differential tube stage, the HA-3A uses proprietary output transformers to generate both single-ended and balanced headphone outputs. The secondary windings of the transformers create an inverted phase, forming a true balanced output derived directly from the transformer. Both balanced and single-ended connections are native outputs rather than adapted signal paths.

Impedance-matched headphone outputs

To accommodate a wide range of headphones, the HA-3A includes three impedance settings optimized for low, medium, and high impedance loads. This allows the amplifier to maintain stable power delivery and consistent tonal balance whether you're using sensitive portable headphones or high-impedance full-size designs.

Multiple headphone connections

The front panel provides three headphone outputs to match different cables and listening needs. A 6.35mm single-ended output supports traditional headphone plugs, while 4.4mm balanced and 4-pin XLR balanced outputs provide higher channel separation and compatibility with balanced headphone cables. The 4.4mm output is tuned to work well with higher-sensitivity headphones.

Clean power delivery

Power conversion is handled by a 22DE4 gas rectifier tube, selected for its ability to minimize interference while converting AC power to DC. This design helps reduce noise before it reaches the amplification stages, supporting a lower noise floor and stable operating conditions across long listening sessions.

Handwired point-to-point construction

The internal circuitry of the HA-3A is assembled using point-to-point wiring rather than printed signal paths. This method shortens signal paths and allows careful component placement, contributing to improved conductivity and easier long-term servicing. The approach reflects Cayin’s emphasis on durability and electrical clarity.

In-house power transformers

Cayin designs and winds the HA-3A’s power transformers in-house, focusing on high inductance and efficiency. Reinforced shielding reduces electromagnetic interference and mechanical noise, helping the amplifier maintain consistent performance in real-world desktop environments.

Precision volume control

Volume adjustment is handled by a high-performance dual-unit ALPS potentiometer rated at 50KA ×2. This component provides smooth operation and accurate channel balance, allowing for precise control at both low and high listening levels without abrupt changes.

Anti-interference and protection features

Special shielding and anti-shock design reduce microphonic effects commonly associated with vacuum tubes. A built-in 60-second start-up delay circuit protects downstream equipment and minimizes audible pop noise when powering on the amplifier.

Stable desktop design

Three oversized aluminum foot pads provide shock absorption and stability on hard, flat surfaces. The two-rear and one-front self-leveled layout compensates for the additional weight of the power and output transformers, keeping the amplifier firmly planted during use.

Dual input connectivity

The rear panel includes both balanced XLR and single-ended RCA inputs. Balanced inputs pass through dedicated input transformers, combining positive and negative signal phases into a single-ended signal before amplification. This allows seamless integration with a variety of DACs and source components.

Product highlights

• Transformer-coupled, balanced-driven tube headphone amplifier
  
• Single-ended two-stage vacuum tube circuit
  
• Impedance-matched outputs for low, medium, and high impedance headphones
  
• 6.35mm single-ended, 4.4mm balanced, and 4-pin XLR balanced headphone outputs
  
• Point-to-point handwired internal construction
  
• In-house designed power and output transformers

Specs

• Amplifier type: Vacuum tube headphone amplifier
  
• Input connectors: XLR ×2, RCA ×2
  
• Output tubes: JJ 6V6S ×2
  
• Driver tubes: JJ 12AU7 / ECC82 ×2
  
• Rectifier tube: RCA 22DE4 ×1
  
• Headphone outputs: 4-pin XLR balanced, 4.4mm balanced, 6.35mm single-ended
  
• Rated output (per channel, low / medium / high impedance):
  
• 4-pin XLR balanced: 600mW / 750mW / 850mW
  
• 4.4mm balanced: 230mW / 350mW / 400mW
  
• 6.35mm single-ended: 400mW / 600mW / 700mW
  
• Frequency response: 18Hz–30kHz ±3dB
  
• THD+N: 0.2% (1kHz, 200mW)
  
• Signal-to-noise ratio: 100dB (A-weighted)
  
• Sensitivity: 300mV–480mW
  
• Headphone impedance range: Low 8Ω–64Ω, Medium 65Ω–250Ω, High 251Ω–600Ω
  
• Power consumption: 80W
  
• Operating conditions: 32°F–104°F (0°C–40°C), 20%–80% humidity
  
• Storage conditions: -4°F–158°F (-20°C–70°C), 20%–90% humidity
  
• Dimensions: 12.0 in × 10.2 in × 6.7 in (306 mm × 260 mm × 170 mm)
  
• Net weight: 26.5 lb (12 kg)

What’s included

• Cayin HA-3A headphone amplifier
  
• Matched vacuum tube set installed
  
• Vacuum tube protection cage
  
• Power cable
  
• User documentation