My turn to post an iTube2 review!
The review system consisted of the following:
Bluesound Node 2>Black Cat Silverstar 75>iFi SPDIF iPurifier>Mojo Audio Mystique v2+ NOS DAC>Mojo Audio Lucent Ribbon Interconnects>Karan KA-I180 Mk2 Integrated Amp or Clones Audio 25iR Integrated Amp>Zu Event Speaker Cable>Fritzspeakers Morel 6
I inserted the iTube2 between the DAC and the two integrated amps I had on hand. The unit was on 24x7 during the review period – it runs warm, but not alarmingly so and cooled quickly once I turned it off.
I started off in Buffer Mode, with 0db gain. Setting the tube to SET, I liked the increased body, palpability and dimension added to instruments. These positive attributes were more prevalent when using the Clones amp vs. the Karan (no surprise here given the price and topology differential between these amps). What I found was acoustic guitars and other acoustic instruments had their focus shifted lower a bit, balancing the sound of the instrument’s body with strings vs. a slight emphasis on strings without the iTube2 in place. The Karan amp has what I’d call a chunky, percussive sound – its damping factor is a ridiculous >1800, so it controls your woofers like nobody’s business. The iTube2 ever so slightly dulled the percussive nature of the Karan, but I still felt the positive attributes outweighed this small change in the Karan’s basic sound. The Clones was simply better across the board with the iTube2 in place with these settings.
Staying with Buffer Mode, 0db gain, I cycled through “Studio” and “Push-Pull” settings for the tube. Studio brought everything in line with the plane of the loudspeakers, negatively impacting the perception of depth and pushed some sounds hard left/right to the speaker locations – I’m an imaging freak, so this setting was a non-starter for me. Push-Pull was a mix of SET/Studio, but I still felt SET was the better overall setting, so that’s where things stayed.
I use a spare bedroom as my listening room – it’s small, square and prone to lumpy bass response, but is well treated with GIK products. I experimented with the XBass settings and didn’t like them at all on either amp. They did indeed add bass, but I felt it overpowered the room and muddied up the presentation. It’s likely a larger space would see some benefit from this function, but it just didn’t work with my room/setup.
In terms of 3D Holographic, I experimented with this quite a bit, but ultimately settled with it out of the circuit as well. The default setting for loudspeakers was better than the +30 setting, increasing depth for me more than width, but it robbed some of the density of images. The Karan amp especially highlighted this – it has a tonal density to it that really places instruments in space. When engaging 3DHolographic, the space did get larger/deeper, but the tonal density I love in the Karan went down a notch and images became more amorphous.
Then I went to Buffer Mode, with +9db gain and everything got better. SET now had not only the added body and dimensionality, but the chunkiness and percussiveness of the Karan amp was back in full force. I liked everything about this sound, but…there’s always a but…I started to hear some raspy distortion on transients and the Karan’s volume control had very little usable range before everything got really loud. Unfortunately the +9db setting was overloading the input stage on the Karan. I switched to the Clones to see if this setting worked there. The Clones volume control had more usable range than the Karan, but the raspy distortion during transients on the Karan went to full on crackling on the Clones. Although Buffer Mode with +9db gain sounded the best overall, I was unable to use these settings. Sigh…
At this point I switched to Preamp Mode, 0db gain and the volume pegged. There was definitely more gusto to the presentation vs. Buffer Mode. It was a propulsive, in-your-face sound, but I felt like it was maybe too much of a good thing. If you can imagine 5 performers on a stage as balloons, with some space between them, Preamp Mode struck me as blowing up all of the balloons until they touch each other – bigger yes, bolder yes, but lacking some of the finesse and space between instruments that makes up a credible soundstage. It struck me as cramped and I just wasn’t able to relax into it. I also felt like the spread between the softest and loudest passages had actually narrowed a bit – i.e. if 1 is the softest sound in Buffer Mode and 10 is the loudest, I felt like those numbers were more like 2 and 9 in Preamp Mode.
After playing around with all the settings in Preamp Mode, I ended up back where I started – Buffer Mode, with 0db gain, tube set to SET, XBass and 3D Holographic out of circuit.
To me, these were the settings which provided the best clarity, increased body and dimensionality, improved timbre, improved sense of the acoustic space in a recording, and best balance of relaxed, yet propulsive sound. While the amount of these improvements varied between the two amps I tried, and there were other very slight trade-offs here and there, they were all present to varying degrees and improved the overall sound of both amps.
So there you have it – something that is modest in cost, has some cool features that may improve specific aspects of your system and which improves the overall sound of very different amps at very different price points – well done iFi!
