Preface
Before I begin, I'd like to preface this article by stating my intent. This article is not meant to be a detailed review of the iBasso D6, nor do I attempt to make direct comparisons against similarly priced amps, as this is the first portable device with which I've had any experience. The goal of this article is to share a few observations regarding my iBasso D6 purchase, and to describe it's compatibility with several headphones that I own.
The adventure begins
I purchased my first pair of "custom" IEMs, the Ultimate Ears Reference Monitors (UERM), to primarily to listen to FLAC files from my computer, and secondly to serve as the basis of a portable system which I intended to assemble in the future. I quickly discovered that playback from my desktop system was terrible even with FLAC files, because the system is inherently noisy and the performance of the on-board sound chip is extremely poor. So began a quest to find a suitable external DAC/amp which ultimately lead me to the subject of this article - the iBasso D6 Fer-de-Lance.
What really triggered my initial search was viewing the Head-Fi TV, Episode 003: Cypher Labs Algorhythm Solo: A Game Changer review by jude. Being new to Head-Fi I have no experience with what is possible with respect to portable units, so this review intrigued me. I wondered if it was possible to achieved high quality desktop performance from a portable system, albeit at a lower cost. I began my adventure into the realm of portable headphone devices by immersing myself in the many Head-Fi threads which discussed portables. After much searching, the iBasso D6 seemed to fit the bill from a portable DAC/Amp perspective, and at $275 it also fit my lower cost requirement.
After having made my decision to purchase the D6, I navigated my way through the multitude of models listed on the iBasso site. I found the D6, and placed my order on a Wednesday. I received a package via UPS the following Monday - all the way from Shenzhen, China to the San Francisco Bay Area, CA, United States. From order to delivery to my door in 5 days. I was very impressed with the delivery time, and the order process was smooth, a good sign indeed.
Getting down to business
With the unit in hand, I proceeded to take the D6 through its paces by first using it as a USB DAC/amp connected to my Windows7 desktop. Once connected, Windows recognized the device and automatically installed the iBasso D6 device driver. Once the driver is properly installed you'll see "Speakers (USB): 100%" when mousing over the Speaker icon in the System Tray (Note: If you sometimes switch to other USB ports on the same machine, as I do, you may need manually check that the iBasso is set as the Default device for Playback as this did not occur automatically when switching ports for the first time).
Not wanting to initially risk my more expensive cans, I began my first auditioning session by connecting my 64 ohm Sennheiser HD280 just to check power levels. For "normal" listening levels with the HD280, I set the volume control to about 10:00 with the gain switch set to low. I played The Alchemist track from the Acoustic Alchemy - Back On The Case album, which sounded thin with the HD280. The next track, Jamaica Heartbeat, had more bass and sounded fuller, but was wanting more. The amp checked out and all seemed to sound OK, so I decided to move on to listening to the UERM.
As one would expect, everything was much cleaner and more detailed with the UERM. This was closer to the sound I was expecting. The thick warmth of the HD280 was replaced by the welcomed relaxed openness of the UERM. The other improvement, which became immediately apparent, was the lack of spurious noise from my desktop. As previously mentioned, my primary desktop system is notoriously noisy which is why the UERM had not seen much use with this computer. In the past, with the UERM plugged directly to the computer headphone jack, I would hear buzzing while scrolling pages up and down, clicking from the flashing cursor, and clicking from other on-screen cursor movements. Now with UERM driven by the D6, all of the clicks and buzzes have been banished from my system. For the first time, my desktop system is silent. Well, nearly. If I paused the music, a small amount of hiss was barely perceptible when the volume control was turned up to full volume. One other point worth mentioning is that when turning on the D6, due to the UERM's sensitivity, an annoyingly loud pop can be heard. Even if the UERM is plugged in shortly after turning on the D6, a pop could be heard when inserting the 3.5mm mini-plug into the D6 headphone jack. Waiting for 15-20 seconds before plugging in the IEM mitigated the problem. This was not an issue for less sensitive full sized headphones, as only a mild click could be heard at turn on.
Back to the sound
For volume levels suitable for all day listening with the UERM, I set the volume control between 9:00 and 10:00 with the gain switch in the low position. I then began to run through my usual list of reference material - from Jennifer Warnes and Patricia Barber for female vocals, to the Eagles - Hotel California and Spongle for bass, the original soundtrack from Gladiator for an orchestral piece with a large dynamic range to Warren Bernhardt, Jim Hall, Special EFX, Fourplay and Pat Metheny for a mix of jazz artists.
After having listened to a variety of music, I would characterize the performance of the D6/UERM combination as merely good, as the D6 did not approach the Benchmark DAC1 PRE in terms of overall power, detail and resolution. Looking back over my session notes, my comments - although generally favorable - also included remarks like almost muffled vocals, slightly veiled mids and highs, some congestion during loud passages, and some hardness. Not totally unexpected given the notable differences in design goals and price points between the two units. The D6 being a small, battery/USB powered portable USB DAC/Amp, and the Benchmark being a full sized DAC/Amp Pre-amp designed for home based systems. My initial impressions of the D6/UERM paring could be summed up as fair to good.
Next up was the Sennheiser HD800. The HD800 required a slightly higher volume setting, with the volume set to about 12:00 with the gain switch set to low for "normal" listening levels. With the D6, the HD800 was a step up from the UERM. The D6 seemed to power the HD800 well. The overall sound was balanced, and the sound was more open and detailed as compared to the UERM. Bass with the HD800 was tight but a little weak, and the highs tended to be a bit bright. When compared to directly to the Benchmark, the sound from the D6 was not as open, detailed, or transparent. The D6/HD800 combination, although better than the previous paring, could only be summarized as good.
The last headphone in this comparison is the orthodynamic HiFi-MAN HE-6. For the HE-6, I set the volume control between 2:00 to 4:00 for normal listening levels depending on recorded level of the material. It quickly became apparent that this was a less than ideal match. From the start, the bass was very sloppy to the point of being distorted. The highs were scratchy, and often distorted badly on many passages. The sound at low volumes was generally good, but it was clear that the amp was easily strained on loud dynamic passages. This was not a surprise, knowing full well that these orthos would be difficult to drive. I was about to write off the D6 as insufficient for driving the HE-6, but I went back and re-read much of the iBasso D6 "Fer-de-Lance" USB DAC/Amp thread and I came across several posts suggesting a switch from USB to battery power for better performance (Many thanks to jamato8 and HiFlight for the suggestion).
The switch to battery power was nothing short of phenomenal. Gone was the sloppy bass, scratchy highs, and other forms of distortion caused by pushing the amp to the point of clipping. Back was the solid bass, midrange clarity, and fine level of detail that I've come to expect with the HE-6. The highs were still a bit hard, but the overall sound was much cleaner on battery power. Would I hear similar improvements with my other headphones? To answer that question, I would have to go back and re-evaluate the performance of the D6 with the UERM and HD800.
With the D6 now switched to battery power, everything seemed to open up when listening to both the UERM and HD800. There was much more detail and air on nearly every recording. The veiled sound that I originally noticed with the UERM was lifted, as was much of the congestion that was previously heard with both the UERM and HD800. The sound was closer, in detail and power, to the sound I experience when listening directly from the Benchmark. Overall, the sound went from being good to very good for both the UERM and the HD800. The other benefit of this change was a slight reduction in background noise. The hiss that was slightly audible at full volume when on USB power was reduced even further on battery power. The simple switch from USB to battery power not only reduced the amp's tendency to clip, but also produced a lower noise floor, tighter bass, cleaner mids and highs, and a more open sound overall. I was very impressed by this transformation. Needless to say, battery power mode is now my permanent setting for all listening configurations.
(Note: When switching between battery and USB power, it's always been my practice to first turn off the D6. Fortunately, I have not experienced any problems when switching between battery and USB power with my stock D6.)
How loud is loud?
Loudness can be subjective, so I thought it might be helpful if I provide a point of reference for volume levels one might expect when listening to the D6/HE-6 combination. Although I consider the volume levels experienced from this combination adequate for my tastes, they may not, of course, be adequate for your needs.
To establish a point of reference, I ran a simple check using test tones and a RadioShack sound level meter. To ensure my results are repeatable, I use a simple setup fashioned from a 6"x6"x3/4" headphone mounting board with a 1" diameter hole drilled through the center. The pick-up of the sound level meter is seated in the 1" hole with an o-ring to prevent sound leakage from the mounting board opening. With the mounting board in a horizontal position, I place the earcup flush with the mounting board surface, centered directly over the pick-up. I began the test with the volume control set close to the 4:00 position (the third dot counterclockwise from the end). Using the 1kHz one third octave warble tone at -20dB track from the Stereophile Test CD1 (ripped to FLAC of course), I observed playback level of 72.5 dB C-weighting as measured from the meter. At full volume, the maximum value registered was 75dB.
These playback levels are by no means loud. However, many of the sonic traits I enjoy most from the HE-6, detail, transparency, tonal balance, etc., are still present even at these subdued volume settings. Achieving adequate gain from the D6 was not an issue with the other headphones I own. The HD800, would produce 80 dB when set to 2:30. Unfortunately, because I'm unable to objectively measure the output level of the UERM's, the only UERM guidance I can provide is that they are more efficient than the HD800, and as such require a lower volume setting to achieve the same 80 dB output level.
The Verdict
I've had the iBasso D6 for about two and a half weeks. I've experimented with a number of different configurations, and I've come to the following conclusions. I can use this device with any of my Windows computers, and I can go completely portable (I believe I see a Cowon X7 in my future to house my FLAC collection). The D6 is reasonably priced. It strikes me as a surprisingly decent DAC/amp combo that can server up my FLAC music library (I'm listening to The News from Benedetti Meets Diana Krall - Heartdrops album at the moment, and my toe has been happily tapping away to the beat - great song), and it has sufficient power (in battery mode) to drive "all" of my cans to levels I feel are adequate for long periods of daily listening.
Does the D6 have "all" of the power and headroom I would like for my orthos? Well, no. You will not be able to approach anything near ear splitting levels with the HE-6 paired with this little portable. But given everything else the D6 can do well, it quite handily suits 90% of my needs.
As mentioned at the outset, my intent was not to make direct comparisons against other portable DAC/amp combinations. However, what I can say is the D6 provides substantially improved performance over my desktop's stock sound card and although it's performance was in no way equal that of my home based DAC/amp costing many times more, it still brought me much closer to that sound than I thought would be possible from a portable DAC/Amp at this price point. For me, based on price, performance, and functionality, the iBasso D6 Fer-de-Lance is definitely a worthwhile addition to my growing collection of headphone related toys.
Addendum
I understand a number of Head-Fi members have had good results with swapping operational amplifiers(op-amps) with the D6. I've not had any experience with doing so, but if I do experiment with the option in the future, I'll update this article with any new findings.
Related Toys Mentioned
Source(FLAC): Compaq-Presario CQ5218F Desktop running Windows7, Logitech Squeezebox Touch
Headphones: Ultimate Ears Reference Monitors, HiFiMAN HE-6, Sennheiser HD800
DAC/Amp: iBasso D6, Benchmark Media DAC1 PRE
