tube amplifier with independent volume controls

The TA-68 is a fully-balanced desktop tube headphone amplifier built around tube rectification, 12AU7 preamplification, 6C19 current amplification, and a capacitor-coupled output stage. It provides XLR, 4.4 mm, and RCA inputs alongside 4-pin XLR, 4.4 mm, and 6.35 mm headphone outputs. Independent left and right volume controls, isolated transformer power supplies, and a 45-second protection delay support precise, controlled listening with a wide range of high-impedance headphones.

Fully-balanced signal path

The TA-68 uses separate tube circuits for the left and right channels from input to output. This fully-balanced architecture supports stronger channel separation, clearer spatial placement, and a quieter background when used with compatible balanced sources and headphones.

Tube rectifier architecture

Two 5U4G tubes provide high-voltage rectification, with independent anode voltage supplied to the left- and right-channel circuits. The tube-based power stage contributes to the amplifier’s smooth, full-bodied tonal character.

12AU7 tube preamplification

Two matched and screened 12AU7 dual-triode tubes handle voltage amplification. Their role in the signal path gives the TA-68 a warm, rounded presentation while retaining detail and clarity during extended listening.

6C19 tube buffer

Each channel uses two matched 6C19 power tubes for current amplification. This four-tube buffer stage supplies the drive required for headphones with impedances from 60 to 600 ohms.

Capacitor-coupled output

A classic capacitor-coupled output topology preserves the tonal qualities of the tube circuit while isolating the headphones from direct current at the output stage.

Premium audio capacitors

Vishay audiophile capacitors are used for signal coupling, while audio-specific Nichicon capacitors handle power-supply filtering. Together, these components support a smooth tonal foundation, controlled treble, and consistent signal transfer throughout the amplifier.

Dual transformer power supply

Two low-noise, low-flux-leakage EI transformers provide separate power feeds for the left and right channels. Isolating the channel supplies helps reduce inter-channel crosstalk and supports the TA-68’s measured channel separation of up to 80 dB in balanced operation.

Independent channel control

Separate volume knobs allow the left and right channels to be adjusted independently. This makes it possible to correct channel imbalance, compensate for recording differences, or fine-tune image placement without affecting the opposite channel.

Balanced and single-ended inputs

The rear panel includes stereo XLR and 4.4 mm balanced inputs, along with a stereo RCA input for single-ended sources. A front-panel selector provides direct switching between balanced and line-level input modes.

Three headphone outputs

The front panel provides a 4-pin XLR balanced output, a 4.4 mm balanced output, and a 6.35 mm single-ended output. These connections accommodate many full-size headphones without requiring an additional adapter.

Delayed startup protection

A relay-based protection circuit applies a 45-second warm-up delay when the amplifier is powered on. The delay allows the tubes to stabilize before the headphone outputs engage, while also reducing power-on and power-off thumps and limiting inrush current to connected drivers.

Swappable tube design

All tubes are socket-mounted, allowing compatible replacements from different manufacturers to be installed. Tube changes can alter the amplifier’s tonal balance and presentation while preserving the original circuit design.

Aluminum alloy chassis

The TA-68 uses an aluminum alloy enclosure with a sandblasted front panel and a ventilated protective tube cage. The metal chassis provides structural support and helps shield the internal circuitry from external electromagnetic interference.

Product highlights

• Fully-balanced left and right signal architecture
  
• Two 5U4G rectifier tubes
  
• Two matched 12AU7 preamplifier tubes
  
• Four matched 6C19 buffer tubes
  
• Capacitor-coupled headphone output stage
  
• Vishay coupling capacitors
  
• Nichicon audio-grade filter capacitors
  
• Independent left and right volume controls
  
• Dual isolated EI power transformers
  
• XLR, 4.4 mm, and RCA inputs
  
• 4-pin XLR, 4.4 mm, and 6.35 mm headphone outputs
  
• 45-second relay protection delay
  
• Socket-mounted, swappable tubes
  
• Aluminum alloy chassis with tube cage

Specs

• Model: TA-68
  
• Product type: Balanced tube headphone amplifier
  
• Power supply: AC 100–120 V or AC 220–240 V
  
• Balanced input connections: Stereo XLR and 4.4 mm
  
• Single-ended input connection: Stereo RCA
  
• Balanced headphone outputs: 4-pin XLR and 4.4 mm
  
• Single-ended headphone output: 6.35 mm
  
• Rectifier tubes: Two 5U4G
  
• Preamplifier tubes: Two 12AU7
  
• Buffer tubes: Four 6C19
  
• Balanced output power: 120 mW at 75 ohms, 160 mW at 150 ohms, 200 mW at 250 ohms, 330 mW at 300 ohms, 240 mW at 600 ohms
  
• Single-ended output power: 60 mW at 75 ohms, 100 mW at 150 ohms, 130 mW at 250 ohms, 210 mW at 300 ohms, 160 mW at 600 ohms
  
• Balanced gain: 24 dB
  
• Single-ended gain: 18 dB
  
• Frequency response: 10 Hz–80 kHz, ±0.5 dB
  
• Balanced channel separation: 80 dB
  
• Single-ended channel separation: 71 dB
  
• Balanced SNR: 116 dB, A-weighted
  
• Single-ended SNR: 110 dB, A-weighted
  
• THD: 0.1% at 1 kHz into 300 ohms
  
• Recommended headphone impedance: 60–600 ohms
  
• Startup delay: 45 seconds
  
• Dimensions: 13.0 x 11.8 x 7.3 in (33 x 30 x 18.5 cm)
  
• Weight: 24.3 lb (11.0 kg)

What’s included

• TA-68 balanced tube headphone amplifier
  
• Two 5U4G rectifier tubes
  
• Two 12AU7 preamplifier tubes
  
• Four 6C19 buffer tubes
  
• Protective tube cage