John Darko
Musical Fidelity, now under the stewardship of Pro-Ject’s Heinz Lichtenegger, is bringing back the tube buffer. The cylindrical X-Tube is designed to sit between a source component – a DAC, a CD player, a streaming DAC or a phono stage – and an amplifier to deliver 1) the tonal characteristics of a pair of E88CC tubes and 2) a better impedance match between the source device and the amplifier.
According to the press release, Musical Fidelity’s cylindrical tube will “maximise signal transfer” and “reduce distortion due to wrong impedance matching”. Sometimes a source device’s output impedance isn’t low enough to satisfy the higher input impedance of the receiving amplifier. PS Audio Paul McGowan explains impedance ‘matching’ between electrical components in this video:
McGowan’s talk suggests that the X-Tube could also intercede between a pre-amplifier and a power amplifier.
It goes further: back in 2009, I connected a tube buffer to the TAPE OUT and IN sockets of an integrated amplifier to fatten up its leaner sound. In 2025, I would add an X-Tube to the output of an Eversolo DMP-A6 or WiiM Ultra to beef up their more ectomorphic handling of layer separation (especially the Eversolo).
Here’s Lichtenegger discussing the original tube buffer – the X 10 D – made by Musical Fidelity in the 1990s:
“The legendary X 10 D was a typical Antony [Michaelson] stroke of genius: introducing products and technologies nobody thought about but improving high-fidelity products dramatically at a low cost. Simply by understanding the CD player sounded awful, he tried to find a solution. Nobody at that time understood jitter and digital distortion, which were typical of digital source products. Adding a tube in the circuit made CD players sound enjoyable. The tube somehow acted like a digital filter. On top of that, he realized that CD players had, due to cost-saving, very low-cost, high-impedance output stages (look inside a CD player of the mid-90s, nothing in it!!!), which caused a lot of distortion, especially when using exotic cables. So, simply by adding a perfect low impedance buffer with super high input load and very low output load, he fixed the problem. The sound improvement is amazing. The x 10 D was a huge success and a standard in the audio industry for many years to improve low-cost systems to an audiophile-grade. What is valid for CD players in the 90s is true for cheap DACs, streamers, BT devices, and even AV receivers today. I therefore decided to bring the x 10 D back in its original design with a new, clearer name:the X-Tube”.
Rebutting those who would point to a tube’s additional distortion, noise and possible EQ, Musical Fidelity’s FAQ says:
“This is not correct. The Missing Link’s [X-Tube’s] measurements are as follows:
Distortion from 10Hz to 20kHz, less than 0.003%
Residual noise measured at full output, better than 96dB unweighted
Frequency response 20Hz to 80kHz + 0, – 0.3dB
Crosstalk better than 95d8.
So as you can see, in practice the X-Tube produces no appreciable distortion or noise and does not alter the frequency response. In fact, its technical measurements are better than most source devices.”
According to the press release, the chassis is cylindrical to minimise internal vibrations.
The X-Tube goes on sale this month for €499. I think I might buy one.
Further information: Musical Fidelity
