Review: iFi iTube
Letter from NYC (51) 2016 (7): Buffered
Note on Tube Buffers As a long time tube preamp user, Tube Buffers are almost anathema to me. Many tube preamp designs are inherently buffered. They are also found in the cheaper tube CD players, where a buffered stage is added to the output (different from true tube amplification). For those CDPs with a choice of direct or buffered out, I almost always preferred the sound without the buffer (like Shanling). There have also been some outboard units, which you can insert between components (like Musical Fidelity X-10D), and these I have always found detrimental to the signal. A better way may be using a 1:1 transformer for the purpose, as people have done with the output of the CDP (using trannies like the WE 111C). Indeed, some preamps with transformer coupled output is just that. Even then, I don't always like the sound of it.
The iTube has been well reviewed. See enjoythemusic, TNT, dagogo and positive feedback (I don't agree with the latter's finding of resolution compromise). As you can see, this has been billed as a multipurpose device, but I have used mine mostly as a buffer, testing it as a preamp only briefly. I also did not try out the other sonic algorithms.
Round 1 (HK) I bought this second-hand about two years ago. As Buffer I first tested this in my System B (this iteration), inserting it between the Micromega MyDAC and Ongaku. A slight and attractive added warmth was immediately apparent. Careful comparison revealed no signal loss to speak of. I tried both the 0 db and 6 db gain settings and found little difference between them, and thereafter stuck with the 0 db setting. Impressed, I then put this into my System A, between the Arcam rDAC and Kondo M7 preamp - again, the same finding. I also took out the M7 and used the WE124's volume controls to good effect, though I still prefer a preamp in the chain. As Preamp I briefly used the iTube as preamp in lieu of the Kondo M7. Sound was still very good, but inevitably the dynamics was reduced.
Round 2 (NYC) This time I took it to NYC. I had intended to test it vs my Elekit TU-8500, but I haven't gotten around to it. vs Jadis JPS2 Instead I took it to my friend Paul's (setup here, though he has moved house). His preamp, the expensive Jadis JPS2, unusually has one dedicated input with a tube buffer (more info and links here). This is what he uses with his CDP (and a WBT interconnect). In his words, the non-buffered inputs are "unlistenable". We routed the CDP to the iTube, which was connected to one of the unbuffered inputs of the JPS2 with a run of old Audio Note AN-V. To my ears and surprise, the iTube far outstripped the built-in buffer. The iTube sounded airier, with a larger soundstage and much more dynamics. To assess the effect of the interconnect, we used it to directly connect his CDP to the buffered input: it is better than the resident cable, but the result was still not as good as when the iTube was used. So, there, the iTube beat the Jadis on its home turf!
Conclusions The iFi iTube is the best Tube Buffer I have heard. There is no signal loss and it preserves the full dynamics of recordings. Simply marvellous. With a full-tube system, I don't use this much but it is nice to have on hand in case buffering is needed.