Cayin HA-6A MK2 silver

The Cayin HA-6A MK2 represents six years of evolution since the original 2019 model. This Class A tube headphone preamp stands out with its dual-chassis configuration and versatile operation. Powered by KT88 power tubes, it offers two distinct operating modes and can also serve as a stereo preamp for a complete system.

Separation of functions for minimal background noise

The choice of two separate chassis is the main evolution of the MK2 compared to the original model. This physical separation between the power supply unit (PSU) and the amplifier itself aims to reduce magnetic interference that can pollute the audio signal. The PSU block measures 160 × 297 × 185 mm and weighs 8.2 kg, while the amplifier occupies 285 × 297 × 185 mm and weighs 11.2 kg.

The two units communicate via a 6N silver-plated copper umbilical cable. This type of connection, although less common in this price range, allows power to be delivered with minimal losses while maintaining isolation between sections. The toroidal transformer in the PSU block has been specifically developed for this model, as have the EI-type output transformers that equip the amplifier. Internal shielding and the modular component layout complete this anti-noise setup.

Handmade point-to-point wiring preserves signal integrity by avoiding printed circuit boards that can introduce parasitic capacitances. This traditional, more labor-intensive approach remains prized in high-end tube amplification because it allows the shortest path between components.

Tubes selected for character and stability

The sonic heart of the HA-6A MK2 rests on six carefully matched vacuum tubes. The two JJ GZ34/5AR4 rectifier tubes convert alternating current into direct current to power the subsequent stages. While this function is often handled by semiconductors today, a tube-based approach is retained here to maintain coherence in the sonic signature.

The two JJ ECC82/12AU7 voltage amplification tubes form the input stage. These medium-gain dual triodes offer a good balance between gain and linearity. Their role is to prepare the signal for the power tubes by amplifying it sufficiently while preserving its dynamic characteristics.

The Genalex Gold Lion KT88 power tubes form the last link in the chain. Reissued by New Sensor Corporation after the legendary British tubes of the 1950s, these beam tetrodes are renowned for handling high plate voltages (up to 800 volts) and for their linearity in Class A. Their gold-plated grids, carbonized screen grids, and tri-alloy plate structure contribute to a balanced reproduction across the spectrum. The KT88 is characterized by robust mids, airy highs, and deep, controlled bass.

The single-ended Class A configuration means the power tubes conduct continuously, even in the absence of a signal. This operating mode, energy-hungry (130 W consumption), guarantees optimal linearity since the tubes always operate in their most stable region. The absence of crossover distortion, characteristic of Class AB designs, follows naturally.

Two operating modes to tailor the sound

The front-panel selector lets you switch between triode (TR) and ultralinear (UL) modes, profoundly changing the behavior of the KT88 power tubes. In triode mode, the screen grid is connected to the plate, turning the pentode into a triode. This configuration favors smoothness and naturalness, with expansive soundstaging and a silky midrange texture. Available power drops to 3000 mW per channel on the 4-pin XLR output, 2300 mW on the 6.35 mm output, and 650 mW on the 4.4 mm output.

Ultralinear mode, achieved by partially connecting the screen grid to the output transformer, offers a compromise between pentode and triode characteristics. Dynamics extend, transients become faster, and bass control is enhanced. Power rises respectively to 4500 mW, 3500 mW, and 1000 mW depending on the output. This mode is particularly suitable for orchestral recordings and film scores that demand headroom and impact.

This dual personality allows you to adapt the presentation to the nature of the musical program or personal preferences. A string quartet may benefit from the warmth of triode mode, while a rock concert may call for the firmness of ultralinear mode. Instant comparison between the two modes makes it easy to explore these differences.

Broad compatibility for experimentation

Unlike the original model, which required toggling switches on the rear panel, the MK2 automatically detects the type of installed power tube. In addition to the stock KT88s, the amplifier accepts EL34 tubes (and variants like E34L), 6550, KT66, and even KT150. This flexibility opens the door to sound customization through tube rolling, a common practice in the tube gear community.

EL34s, for example, are renowned for sumptuous mids and a warmer character than KT88s. The more recent KT150s offer higher power and even firmer bass. Each tube family brings its own color, allowing you to fine-tune the presentation according to taste or the headphones used. This modularity is one of the major attractions of tube amplification compared to solid-state solutions.

Three impedance settings to optimize matching

The impedance selector offers three positions: Low (8–64 Ω), Medium (65–250 Ω), and High (251–600 Ω). This setting acts on the output transformer windings, each dimensioned for a specific impedance range. The goal is to bring the amplifier’s output impedance closer to that of the headphones to optimize energy transfer and minimize reflections.

A 32-ohm headphone will logically connect on Low, a 300-ohm model on High. But this rule is not absolute: some users deliberately deviate to alter damping factor and thus frequency response. An output impedance higher than the headphone’s generally accentuates bass and softens treble, while a closer match tightens the low end and reveals more detail.

This fine-tuning option is particularly useful with planar magnetic headphones, often current-hungry, or with certain high-impedance dynamic models like the Sennheiser HD 600/650/800. Compatibility spans from 8 to 600 ohms, covering most hi-fi headphones on the market.

Comprehensive connectivity for every use case

Three headphone outputs are featured on the front: an unbalanced 6.35 mm jack, a balanced 4.4 mm (Pentaconn) mini-jack, and a balanced 4-pin XLR output. The latter delivers maximum power and is the preferred choice for headphones with compatible cables. The 4.4 mm output offers a good balance between performance and convenience, while the 6.35 mm output remains the most universal.

On the rear, there’s an unbalanced RCA input and a balanced XLR input for connecting various sources: CD player, DAC, network player, or a turntable equipped with a phono preamp. The presence of a preamp RCA output (up to 6 V, 20 dB gain) turns the HA-6A MK2 into a true tube preamp for a complete system. It can thus be used ahead of a power amplifier for speakers or directly with active speakers.

This versatility enables multiple setups: headphone-only listening, speaker listening with the HA-6A MK2 as a preamp, or a mixed use depending on the time of day. The included aluminum remote control makes it easy to adjust volume and mute from a distance—a welcome comfort during long listening sessions.

Technical Specifications

Architecture and Construction

• Dual-chassis architecture
  • Separate chassis for the power supply and amplifier to minimize magnetic interference
  • EI output transformers and a toroidal transformer specially designed for the HA-6A MK2
  • Internal shielding and optimized modular layout for ultra-low noise
• Point-to-point construction for maximum fidelity

Key Features

• Point-to-point construction for maximum fidelity
• Dual-chassis architecture reducing interference
• Triode and ultralinear modes for flexible sound rendering
• Broad tube compatibility for tailored sound tuning

Tubes

• Power tubes: 2 × Genalex KT88
  • Single-ended Class A
  • Excellent linearity
• Voltage amplification tubes: 2 × JJ ECC82 / 12AU7
• Rectifier tubes: 2 × JJ GZ34 / 5AR4
• Rigorously selected for sonic character, stability, and longevity
• Compatible with other power tubes: 6550, KT66, KT150, etc., for maximum flexibility

Connectivity

• Inputs: 1 × balanced XLR, 1 × unbalanced RCA
• Headphone outputs
  • 6.35 mm unbalanced
  • 4.4 mm balanced
  • 4-pin balanced XLR
• Preamplifier output: 1 × RCA
• Compatible with a wide range of headphones and usable as a tube preamp for external amplifiers or active speakers

Operating Modes

• Triode mode (TR)
  • Smooth, warm, and natural sound
  • Ideal for vocals, jazz, and acoustic music
• Ultralinear mode (UL)
  • Extended dynamics
  • Tighter bass and improved control
  • Suited for orchestral music and film soundtracks
• Easy selection from the front panel for instant A/B listening
• Aluminum remote control included for volume and mute

Technical Specifications

• Balanced 4-pin output power
  • UL: 4500 mW + 4500 mW
  • TR: 3000 mW + 3000 mW
• Balanced 4.4 mm output power
  • UL: 1000 mW + 1000 mW
  • TR: 650 mW + 650 mW
• Unbalanced 6.35 mm output power
  • UL: 3500 mW + 3500 mW
  • TR: 2300 mW + 2300 mW
• Frequency response: 10 Hz – 26 kHz (± 3 dB)
• Total harmonic distortion (THD): 0.3% (1 kHz @ 200 mW)
• Signal-to-noise ratio: 104 dB (A-weighted)
• Impedance matching: 8 Ω – 600 Ω (selectable L / M / H)
• Preamplifier output voltage: 6 V max
• Preamplifier gain: 20 dB
• Tubes used: ECC82 × 2, KT88 × 2, GZ34 × 2
• Inputs: 1 × RCA, 1 × XLR
• Preamplifier output: 1 × RCA
• Power consumption: 130 W
• Dimensions (W × D × H)
  • PSU: 160 × 297 × 185 mm
  • AMP: 285 × 297 × 185 mm
• Net weight
  • PSU: 8.2 kg
  • AMP: 11.2 kg