iFi Audio iTube Active Tube Buffer/Preamplifier

October 4, 2013
6 mins read


5 Stars

Body, soundstage, height and kick: this diminutive tube buffer stage and preamp combo has it all.

TUBE BUFFER? ANYONE remember the Musical Fidelity X10D Missing Link? It was a tube-based buffer stage designed to convert that shrill, fatiguing sound of budget CD players of the mid-to-late ‘90s and turn it into something resembling enjoyable music.

This was a game changer for Musical Fidelity, the first of the X series and a sorely needed success for Anthony Michaelson after a few iffy years of reliability issues (overcooked A1 Class-A integrated amplifiers, for instance). With a fervour whipped up by mags like Stereophile, this product sold like hotcakes. There were many other X series components to follow, but the X10D was the product of its time and place, and at a price any budding audiophile could afford without entering financial hardship.

WD-iFi-iTubeLooking back fondly at the Missing Link, it wasn’t without its drawbacks. Certainly it added that tube warmth and a lower end bloom to the sound, but this was at the expense of micro-detail and dynamics. What it did do was to present an even load to the amplifier, so at its heart the X10D was an impedance-matching circuit in a cylindrical tube with a valve output stage – this was used in order to produce something approaching the lush  sound found in Class-A solid state amps, and particularly proper tube designs.

iTube Specs

Fast-forward to 2013 and iFi Audio have re-imagined the X10D with a completely new set of design parameters. As well as doing tube buffer duties it can also be used as a preamplifier for those with a single source (or a source selector box such as Pro-Ject’s natty little Switch Box S), while the Digital Antidote Plus circuit is designed to eliminate the sometimes harsh ‘ringing’ of poorly designed analogue stages found in some digital source components.

A single GE 5670 NOS (new old stock) tube resides within the sleek aluminium enclosure. This is soldered onto the board and as such isn’t easily replaceable. Happily, iFi claims a crazy tube life of 100,000+ hours, so realistically it’ll never need changing. It won’t please those of us into tube rolling, but those handy with a soldering iron could have a crack at replacing the tube (check the warranty first though!)

Also contained within the now-familiar iFi Micro casework is what’s called 3D Holographic Sound, designed to (in iFi’s own words)  “address the issue of how the human head ‘hears’ where lower frequencies are less well defined than upper frequencies.”

This circuit essentially allows the listener to tailor the sound according to his or her listening environment. Sitting at the computer with your speakers in a near-field position? Simple, just set the DIP switches to WIDE and the resultant output suddenly has a broader soundstage.

I mentioned DIP switches – another major departure from the altogether simpler X10D, allowing 0 or +6dB gain for both the buffer and preamp sections. In fact, the preamplifier can be switched right out, turning the iTube into a buffer only. These are located on the underside of the device, and if you have eagle eyes, you’ll be able to make out a ‘how to do it’ diagram printed in silver. iFi have thoughtfully included a card replicating the information so a magnifying glass isn’t really necessary.

Otherwise, the iTube is a pretty uncluttered component: toggle switches are in situ for the three 3D Holographic Sound settings, and an on/off toggle for Digital Antidote Plus. Next to these is the volume knob, which also acts as the on/off switch. The rear panel houses both sets of RCA sockets (in/out), while the supplied wall wart connects via a side entry jack.

Four bump-on self-adhesive feet are included for purchasers to apply to the iTube’s chassis, and also contained within the beautifully designed packaging is a right angle adaptor for the PSU cable, along with a pair of budget RCA cables.

Oh yes, I must rave a bit about the packaging – very Apple Computer but in a good way, the carton is so sturdy I could just about stand on the box without crushing the contents.

In Use

The iTube can be used in a variety of configurations as described graphically on iFi’s Facebook page: insert it between a solid state preamp and power amplifier, between a dac and amplifier, or an outboard solid state phono stage and amp, and it’ll instantly turn the source component into an impedance-matched tube output component. That was an intriguing prospect, and after sampling iFi’s other delights (iDac/iPhono/iUSBPower) I was dead keen to try it out. It was time to get cracking.

Listening Session

Sadly, I wasn’t able to use the iTube in my main system. I use balanced cables from my Audiolab 8200CDQ, which can’t be used on the iTube, and at that stage I had my Audio Innovations tube phono stage connected. Never mind then, into the second system it went and I managed to audition three configurations – between my passive preamp and ASL mono tube amps, between my own iFi iDac and pre, and finally I slotted the iFi in between my little Aune X1 MK2 dac and Squeezebox Duet. In addition to the Duet, the other source components were an Apple Macbook Air running Audirvana Plus software, and my sweet Pink Triangle LPT and Sugden PA4 Masterclass phono preamp. Loudspeakers were proudly supplied by Omega in the form of their delicious little hemp-coned single driver Super 3 XRS.

I decided to try the iDac/iUSBPower/iTube combination at the outset, and this produced quite a surprise. Even though I really enjoyed the sound quality, the addition of the iTube improved the system in just about every way. Immediately apparent was the broader soundstage and height of the audio image. Next on the list was a subtle improvement in the quality of lower frequency reproduction: bass and drums seemed to have more ‘body’  (kick drums for instance seemed better defined and speedier), while I found it easier to follow complex bass guitar lines.

Midrange detail wasn’t affected at all, yet there was a silkier, more involving quality to what I was hearing. John Lee Hooker’s vocal on The Healer grew in size between the speakers compared to how I’d heard it pre-iTube, while Carlos Santana’s guitar leaped from the Omega’s in a revealing and realistic fashion.

This was using the iTube as a buffer only.  Engaging the 3D Holographic circuitry broadened the soundstage even further, and while entertaining, I preferred the buffer-only effect in my small room – it just sounded a bit more believable to my ears. Engaging Digital Antidote Plus also created a sonic improvement, taming a tiny amount of sibilance from the Omega hemp cones and rounding the top end off in an oh-so- subtle way.

This was terrific stuff from such a humble little component. Somehow it managed to elevate the system to a higher level and although the singular effects were quite subtle, the combined effect took a very good system to the verge of affordable hi-fi greatness.

WD-iFi-iTube2I then decided to plug the preamp outputs into the iTube and as such turned it into a tube pre. Here the results were very similar, only I could now hear improvements across the board while listening to the Duet and Pink Triangle via the Sugden. My guess was (especially in terms of the Sugden) that the preamplifier suddenly had an instant upgrade. Piano, strings and especially the female voice became more realistic and palpable.  Kate Bush’s debut album The Kick Inside just sounded gorgeous on vinyl – especially the stripped down mix on ‘Feel It’, her vocal just soaring from an inky background (accompanied by her piano, of course). I expected to unleash my schoolboy chuckle at the lyrics to that song, but the system sounded so good I just sat there and lapped up the whole album.


I was expecting a subtle improvement from the iTube, but it improved just about every facet of the audible spectrum on my system. That added up to a whole lot of change in sound quality terms, and all of it good.

Who would buy an iTube? Well, I’d say everybody with even the slightest question mark concerning their system’s audio performance, and a hell of a lot who consider their pride and joy to be the bee’s knees.

I’ve had endless hours of enjoyment with my little tube-based system in the past but the way this product coaxed even better sound quality from it was a revelation

So to sum up: at the risk of sounding like a scratched record (heaven forbid), iFi Audio have cracked it with the iTube. It’s a far better sounding and sophisticated proposition than the X10D ever was, and its flexibility and the technology contained within its stylish casework makes it an audio no-brainer. GARY PEARCE


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