In this article, I’m exploring the FX-Audio Tube 05 headphone amplifier and preamp. The Tube 05 features a 12AU7 vacuum tube and tone controls. It’s priced at $119.
Disclaimer: This sample was provided by HiFi College for an honest review. All observations and opinions here are my own, based on my experience with the product.
FX-Audio Tube 05
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Design
Like the majority of FX-Audio’s products, the Tube 05 is a straight-faced black box with a matte finish. The single 12AU7 tube adds a little flair, especially when the unit is powered on. The underside of the tube gets some additional glow from some orange LEDs placed just beneath it. I was happy to see the addition of the vents at the top of the device to help with heat dissipation because those 12AU7 tubes can get pretty warm.
The front face of the Tube 05 hosts an OLED display, 3.5mm and 6.35mm unbalanced outputs and a volume knob/button. When headphones are plugged into the Tube 05, the unit intelligently switches from the Line output to the headphone output.
Around the back are the RCA Line input and Line output plus some additional venting. The Tube 05 can be used as a preamp using the Line out.
The system menu can be accessed by pressing the volume knob or by using the remote. This is where you’ll find the Bass and Treble tone controls plus the option to switch between direct mode and tube mode.
Sound
I want to start this section by talking about the differences between Direct mode and Tube mode. In Direct, the Tube 05 sounds a tad more transparent. Notes are more focused and less distorted. Once it’s in Tube mode, the second-order harmonics kick in and bring with them some subtle colouration. They smooth out some of the harshness of modern digital recordings and introduce a certain musicality.
This amplifier proves less than ideal for sensitive IEMs due to its notably high minimum volume setting, limiting the ability to make subtle volume adjustments. Even at the lowest volume setting (01), I encountered instances where the output exceeded my desired sound level. Having said that, it has a low noise floor and I didn’t experience any background hum or hissing.
This tube amp doesn’t create the same rich tones you’ll find on an OTL amp or one with multiple tubes but the difference the single 12AU7 tube makes is audible. Instrument and vocal notes take on a rounder, more harmonious quality, enriching the sound. This contributes to a pronounced warmth, enhancing the depth and resonance of each note.
Listening to Lunatic Soul’s ‘Walking On A Flashlight Beam’ with the Sennheiser HD650 — the bass is full-bodied, the vocals are upfront and engaging and the soundstage seems so real it feels as though I’m at a live concert. The Tube 05 adds intimacy to the HD650’s vocals and gives the sound an airier feel.
The characteristics of the FX-Audio Tube 05 with its smooth and harmonically rich performance, impart a delightful colouration to the sound. Its gentle distortion and soft clipping contribute to a pleasant saturation, enhancing the overall musicality and depth. Overall, the Tube 05 presents a charming sound, offering a blend of classic warmth and modern fidelity.
Verdict
In summary, the FX-Audio Tube 05, with its glowing orange LED, OLED display, and 12AU7 tube, offers both style and functionality. It intelligently switches between Line and headphone outputs and provides tone controls and mode options through an accessible system menu.
The Direct mode offers transparency, and the Tube mode introduces harmonics that add a pleasant colouration to the audio. While not ideal for sensitive IEMs due to its higher minimum volume, the Tube 05 is a good option for higher-impedance headphones.