The Holo Audio May family of DACs may be unfamiliar to those of you unacquainted with headphones, but the Holo Audio (website) brand indeed has a long history and excellent reputation, and not merely in the desktop space. In fact, Holo Audio was producing large rack-sized gear long before many well regarded headphone-oriented brands existed.
Words and Photos by Grover Neville
One of the most well known early products from Holo Audio was the Spring DAC, along with the various updates and upgrades of that product, which is now available in its third iteration. Again, the Spring DAC was unusual in that it used a discrete R2R topology which converts digital-to-analog by utilization of a Resistor Ladder circuit. Very few examples of these discrete design types of DAC have been produced and brought to market since the early days of digital, though they are experiencing a welcome resurgence thanks, in large part, to brands such as Holo Audio.
Build and Unboxing, Holo Audio May DAC
Tim Connor of Kitsune Hifi, Holo Audio’s stateside distributor, was gracious enough to let me spend ample time at home with the May DAC KTE edition ($5,598 USD), the company’s top-tier representation of May model. KTE Designation features include: hand selected dac modules, KTE exclusive Caps, Holo Audio Caps, DAC module exclusive cover/shields, enhanced USB module w/Titanis 2.0 circuit, silver wiring, Red Nano Fuse and many more mods/improvements. Included also: a remote, DC cable, USB Cable, and a power cable included only for the North American market.
The May DAC represents over three years of R&D and development of the NOS (non-oversampling) technology they have been developing since the original Spring DAC. Uniquely, to my knowledge, among DACs of this type, there is native support for DSD1024 and PCM up to 1.536MHz. Holo audio also states that the new linear compensation circuitry resulting from the use of resistors has addressed many of the issues with NOS DACs. I won’t digress too far into the minutiae of filter topologies, but in a practical sense, I do think they’ve done something interesting here – peeking at the internals of a May DAC has also left me more than a little impressed. This is not your standard “throw-a-chip-in-it” and call it done digital design.
Upon receipt, the May DAC immediately presents itself as a serious piece of hardware. Two chassis are cleverly packed in very cool blue circuit-trace designed boxes. I at first thought I was opening some kind of futuristic VR setup or gaming console, at least until I caught a glimpse of that distinctive orange and black color scheme.
Included are some very thorough materials including a very nice full color manual, a milled metal remote, an umbilical cable for the power supply and main DAC unit and of course an IEC cable. Overall packaging was very nice and the entire experience made the not insubstantial two units a cinch to get out. Thoughtful packaging counts.
Once you’ve got the power supply and main DAC unit unboxed and hooked up, you’re greeted with quite an imposing unit. These are two full size components stacked atop each other, and frankly at the five thousand dollar price point I’d be hard pressed to come up with any source or digital component that has anywhere near the stance, build quality, size or sheer visual wow factor. The Orange accents are very classy, as is the aggressive Kitsune fox head logo.
In terms of functionality, the remote works well, and while some may find remotes and DACs to be head scratchers, the May KTE remote delivers seated access to a multitude of mode and connection options: NOS (non-oversampling) mode, Oversampling, or PCM Oversampling and DSD Oversampling, and then an entire suite of digital inputs including USB, Coaxial, Optical, AES and even I2S. With so many options, having a capable remote to quickly switch sources and compare operational modes was invaluable.
Sound, Holo Audio May DAC
Now we get to the meat of the review, and frankly the most interesting bit. In the standard NOS mode, the sound is different from what I remember of the original Spring DAC that I recall hearing at head-fi meet ups in years past. This unit does not have what I think of as a distinctive R2R warmth, where sounds take on a density often in exchange for perceptual clarity and transient definition.
Here, the May KTE is clear, clean and on first listen…kind of invisible. There is no meaty thumpy low-end like old Theta Gen V units or the like, nor does it have the creamy romanticism of a tubed output Philips TDA1541 chip design. However, at the same time the May does not exhibit the slight grain and edge of many less expensive chip-based DAC designs either. I found the entire frequency spectrum extremely free of extra grain and unpleasant texture, and with a coherency and absence of any edge that wasn’t on the source recording.
As I listened deeper, I could hear that compared to some of my in-house DACs, the May DAC was subtly enhancing my sense of the bandwidth and frequency extension of the sound, and presenting a very realistically, but ever so slightly wider stage than many DACs I am used to. This was always presented in an organic and natural way that kept me coming back to listen again and again.
I did notice perhaps a very slight softening of the highest frequencies, but only in a very minute and unexpectedly pleasing way. The May did not sugar coat harsh recordings to a degree that they lost their fundamental character. When switching from the NOS mode to the Oversampling mode however, I did notice just a slight bit of extra texture and detail emerged. I could perceive the resultant filter tightening and clamping down on the highs in that subtle way that all high-pass filters do – if you’ve ever used a digital parametric eq filter you know what I’m talking about. The effect is not unpleasant, and is perhaps slightly more accurate, though the difference between the NOS and Oversampled modes on the May DAC were closer than maybe any DAC with selectable filters I’ve ever heard. Oversampling engaged, the smooth, grainless nature of every frequency range remained, and the slight tightening up of high frequencies did not fundamentally change my valued impression of the May DAC.
I only had a little DSD material on hand, so while I did experiment with the PCM Only oversampling mode, which as its name suggests, it oversamples everything to PCM, and the DSD mode which does the opposite, I didn’t find there to be an exceptional difference. These are the subtle sound differences between digital formats – those who like a little extra sparkle may enjoy the DSD mode, but in general I found myself not bothering with these modes and enjoying the NOS or plain old OS modes, primarily the former.
This brings me to the next point which is that aforementioned linear compensation circuitry – Holo Audio explains it as such:
“There’s an additional R2R resistor network in the May DAC, that compensates the main R2R ladder. It works like trimming, but trimming is to change the resistor value. This additional R2R ladder is digitally controlled and will accurately compensate the resistor tolerance reaching a variance of 0.00005% tolerance accuracy. . For example, the MSB of 16 bits should have the value of 32768, but due to tolerance, it represents 32700 in real world results. Then that additional R2R ladder will compensate 68 into it. Thus it now becomes 32700 + 68 = 32768. What this means is that it’s likely the most precise Discrete DAC on the market with near flawless linearity, lowest THD and highest SNR of any NOS DAC. The sound is simply something you must experience to fully realize how special this DAC is. It’s a patented technology exclusive to Holo Audio.”
As far as I know, this is relatively unique and presents an interesting and discrete attempt to solve the “resistor-tolerance’ issue inherent in R2R DACs. While I can’t speak to whether or not this additional R2R circuit is responsible for the sound, I do hear the May DAC as being uniquely clean, grainless and coherent, even for R2R DACs which are typically known for their tempered musicality. You’d be hard pressed to find a DAC as smooth and pleasing as this one.
Like other R2R DACs, it has plenty of density, yet without any lower midrange bloat or loss of resolution in the highs. Impact is appropriate to the program material being played, and auditory images are tactile while also having a dynamic weight and substance that few DACs I’ve heard can match.
The tradeoff for all of this? The neutrality and smoothness can sometimes leave you less than wowed on a first listen. Living with the May DAC is a relentlessly music-focused experience, and I think most of us would be lying if we said we didn’t enjoy hearing the gear doing a little editorializing once in a while. Here the May does not budge an inch, consistently offering a version of neutrality which is listenable and musically involving. To the music listener in me, the May whispers volumes. The gear lover in me is somewhat disturbed by the thought that this might be the only digital source I’d ever need.
Conclusions, Holo Audio May DAC
The sound of the Holo May DAC is a bit of an elusive thing to describe. For the R2R enthusiast the May does not trade in the fanciful frequency colorations, college-party dynamics and slam or other antics that some have come to expect. Instead it resides in the company of those rare DACs, most of them at least twice the price of the May, that present auditory honesty in such a refined way that you can’t help but want to listen to music. I listened to my stereo far more frequently than usual when the May passed through my system, and were I buying a standalone DAC in the cost no object category, the May DAC would be on a very short list of extremely serious candidates. For the true digital enthusiast this is a must hear.