Musical Fidelity X-Tube Tube Buffer

Pure Class A tube output buffer with 2x E88CC triodes for enhancing modern digital and analog sources

The Musical Fidelity X-Tube is a modern reimagining of the classic X-series buffer, built into the newly updated X-profile aluminum die-cast chassis. The X-Tube is designed as an intermediary stage between source and amplifier, extending your signal chain and adding tube-like refinement without cluttering your rack with external power supplies or extra boxes.

At its heart is a pure class-A triode line stage based on two 6922/E88CC tubes, arranged so that both process the entire signal in single-ended fashion. This topology, combined with a clean, high input impedance and low output impedance, is engineered to maximize signal transfer while keeping distortion, noise, and frequency response deviations vanishingly low. The result is a presentation with greater depth, space, and harmonic richness, but underpinned by measurements that rival or exceed many solid-state line stages.

Connectivity is straightforward: 1x RCA input, 1x RCA output, plus an RCA bypass for easy comparison or system integration. Use the X-Tube between a streamer, DAC, CD player, or phonostage and your integrated or power amplifier, or between a preamp and power amp as an impedance-matching stage. It can also sit between an A/V receiver and multichannel power amp to elevate the front left/right channels for serious stereo listening. A direct IEC mains input (AC 100–230 V) keeps the setup clean and flexible in a wide range of systems.

The Design

• Single-Ended Tube Architecture: The X-Tube runs both 6922/E88CC tubes in a single-ended configuration, letting each tube handle the full signal for speed and low distortion. This design preserves transient detail and adds a touch of triode smoothness
• Impedance Matching: Tubes naturally present high input impedance, reducing loading on the source and improving overall signal transfer. This helps maintain clarity over long cable runs or with difficult component pairings
• System Isolation: A tube buffer can act as a protective interface between components, reducing the influence of reactive loads. This extra stability helps prevent noise, oscillation, and other system-level issues
• Harmonic Character: Tube stages introduce subtle even-order harmonics that listeners often perceive as warmth or richness. The effect is gentle but can add depth and texture without altering frequency balance
• Warmer, More Engaging Sound: Tubes emphasize even-order harmonics, creating a smoother and more natural presentation than many solid-state designs. This warmth can make long listening sessions more inviting
• Improved Dynamics and Transients: The X-Tube’s triode topology responds quickly to changes in the signal, preserving impact and microdynamics. Music feels more lifelike and energetic as a result
• Reduced Listening Fatigue: Tube buffers avoid the sharpness or glare that can creep into some systems, especially with digital sources. Their gentler harmonic profile keeps the sound comfortable over time
• Enhanced Sense of Space: Many listeners hear greater dimensionality and ambient detail when tubes are introduced into the chain. This added “air” can make recordings feel more open and immersive

Specifications

Type: Pure Class A triode tube output buffer / line stage

Tubes: 2x 6922/E88CC triode tubes

Frequency Response: 20 Hz–80 kHz (+0, –0.3 dB)

THD: < 0.003% (10 Hz–20 kHz)

SNR: > 96 dB unweighted (ref. full output)

Crosstalk: > 95 dB (20 Hz–20 kHz)

Gain: 1 dB

Input Impedance: 470 kOhms

Output Impedance: < 33 Ohms

Inputs: 1x RCA

Bypass: 1x RCA

Outputs: 1x RCA

Mains Input: AC 100–230 V, 50/60 Hz IEC C14 socket

Power Consumption (Standby): < 0.25 W

Dimensions (WHD): 4.25" x 4.13" x 10.79" (108 x 105 x 274 mm)

Weight: 5.05 lb. (2.29 kg)