Chord Blu MK II Digital/CD Transport

Previously, I did an extensive review of the Chord DAVE vs Hugo2 vs Mojo DACs, when driving various headphones, my traditional 2 channel system, and (in what was a turn-my-audiophile-world-upside-down revelation) direct driving high-efficiency single-driver Omega Super Alnico Monitor speakers. I was hoping to include the Chord Blu2 in the review mix, but unfortunately my Blu2 did not arrive until a month or two after I had to return the loaner Hugo2 unit. My original plan was to update that review once I got my Blu2 in, but my experiences over the past couple weeks are such that the Blu2 really deserves its own chapter.

This review may be most helpful if you first scan the original DAVE vs Hugo2 vs Mojo review, where I detail my equipment/biases/expectations/hopes for music, as well as provides a baseline for the core DACs in the Chord DAC family that the Blu2 is intended to enhance and extend. That review can be found here: https://www.head-fi.org/showcase/chord-hugo-2.22209/reviews#review-19435


Hardware

Source setup
MacBook Pro and Mac Mini, running latest OS X, content on local SSD, running Roon 1.3
Bit perfect either direct USB, or via direct ethernet to a Sonore Sonicoriber SE running Roon Bridge to USB, to the DAC
Chord Blu2 CD transport ($10000)

DAC setup:
Chord Hugo2 ($2400)
Chord DAVE ($10000)
Chord Blu2 mScaler ($10000)

Headphone setup
Sennheiser HD800 (with SR mod) ($800 used)
Audio Zenith PMx2’s headphones (heavily modified Oppo PM-2’s) ($1800)
Noble Katana CIEMs ($1600)
MrSpeakers Aeon Flows headphones (closed) ($800)
Grado HP1000 (HP2) legendary old skool headphones ($priceless)

Traditional Two Channel Setup
RCA from DAC to Benchmark AHB2 amp ($3000) to B&W 802D3’s ($22000/pair)

Direct Two Channel Setup
RCA direct to Omega Super Alnico Monitors ($2000/pair)
RCA direct to Omega Compact Alnico Monitors ($1500/pair)
For Chord DAVE and Omegas, XLR direct (in parallel) to JL Audio F112v2 subwoofer ($3700), tuned to room and low end fall off of Omegas (~50Hz)
For Chord Hugo2 and Omegas, no connection to subwoofer
For B&W’s, no connection to subwoofer

DAC settings
For headphones, cross feed set to 2 for DAVE and Hugo2 (no crossfeed setting on Mojo), unless recording is binaural (0 crossfeed)
Neutral filter for Hugo2
PCM+ mode, HF filter off for DAVE (per recommendation when using Blu2)
Dither off, and by default high resolution mode on the Blu2
All DACs volume matched using a SPL meter (at least to the best I could)


Content

At various points, I went through all the music in my “Go-To Chord DAC Demo tracks” that I highlighted in my Chord DAVE vs Hugo2 vs Mojo review, but for these sessions I really focused on the following, either for how much they shined in my previous review (could they shine brighter still?), or how much they fell short (could the Blu save them?):

Murakkaz Ah Ya Muddasin, from “The Splendour of Al Andalus” by Calamus (MA Recordings, DSD64)
Remarkable recording in what sounds to be a majestic and spiritual centuries old cathedral in Spain. With the right equipment, you are transported to a place you’ve never been to but always want to get back to. When the full group joins in, it is profoundly challenging to reproduce the mids and highs without sounding shrill and congested. When the reproduction is effortless, it is magical (to say the least…my jaw drops every time when it’s “right”) If the sound chain is able to maintain that glorious soundstage, it is off the charts. Todd Garfinkle is a magician behind the microphone.

Noche Maravillosa, from “Salterio” by Begonia Olavide (MA Recordings, 16/44.1 FLAC)
Another gem of a recording and performance from Todd. The precision and clarity of the instruments (particularly the percussive ones) is intoxicating and tangible.

Rimsky-Korsakoff: Scheherazade, 1st movement conducted by Fritz Reiner (Analogue Productions Remaster, CD layer from SACD)
The most perfect recording of the most perfect performance I’ve ever heard. Listening to this recording on a transparent system is a life changing experience: you are standing with Maestro Reiner in Chicago as his orchestra reaches for a performance for the ages. A cultural treasure, and worthy of building a world class system around.

Handel: Messiah - Chorus. O thou tallest good tidings by Dunedin Consort (Linn, CD layer from SACD)
Handel: Messiah - Hallelujah by Dunedin Consort (Linn, CD layer from SACD)
A magnificent recording, reconstructing the original version of Handel’s Messiah, with a total of 12 singers. The normal complexity of the piece is captured in a way where you can hear each voice in the chorus, and how it comes together into a larger whole. An amazingly intimate performance when the reproduction chain can manage the complexity and dynamics and not have the soundstage become muddy and flat.

Arnesen: Magnificat - Fecit potentiam by TrondheimSolistene (2l, 24/192 FLAC)
This is such a lovely recording at any quality level, but goes from incredible to other worldly as the chain scales up. The orchestra, choir, and church should all have equal contribution to something far greater than the sum of its parts. When it all comes together, you can feel the three core elements feeding off each, creating a profound joy that is sweeps you into euphoria.

Stardust, from “Duets” by Rob Wasserman (16/44.1 FLAC)
Every track on this album is a gem, but this one is particular is a fantastic test of sound stage and imaging. At its best, you hear each backing voice precisely in space, but still presenting as a harmonious whole. In real life, detail and precision spatial placement isn’t hard and clinical, why should it be in reproduction?

Shamas-Ud-Doha Bader-Ud-Doja, from “Shahen-Shah” by Nusrat Fateh Ali Khan (16/44.1 FLAC)
The first track from what was my surprise 2012 album of the year (see http://thingssoimpossible.blogspot.com/2012/12/2012-albums-of-year.html for that backstory, with the surprise ending). A remarkable supremely spiritual performance by a remarkable man, captured in an “eh” recording. The question for me is what these DACs can do to elevate a middle of the road recording that is worthy of elevation.

One World, from “Session 1” by Sareena Overwater (Blue Coast, DSD64)
One World (Instrumental), from “Session 2” by Sareena Overwater (Blue Coast, DSD64)
Real magic from Cookie. These tracks are wired directly to deeply held memories for me, and the stronger the reproduction chain, the stronger the emotion that they evoke. There are better examples of piano performance and better examples of vocals, but the emotional truth and power of this performance is unmatched. More on this track at the end of this review.

Vous et Moi, from “Night and Day” by Willie Nelson (SurroundedBy Entertainment, 24/96 FLAC)
What if Willie Nelson was in a dispute with his label, got pissed off, and invited the best musicians he knew to the studio to record an instrumental album in full surround? Yeah, this actually happened, and it is as awesome as you think it is. The album is amazing in a musical surround setup, but a proper 2 channel system puts you right in the middle of the band. Incredible stuff.

All I Want, from “After Blue” by Tierney Sutton (BFM Jazz, 16/44.1 FLAC)
Tierney Sutton has a striking clear and present vocal style, and that is on full display on her “After Blue” album of Joni Mitchell standards. I continue to be amazed how ever better DACs extract ever more nuance and subtly of performance from top tier vocalists. It is a joy to hear the depth of craft and art of vocal performance on tracks like this.

Rosa fresca, from “Il viaggio d’amore” by Arianna Savall and Petter Udland Johansen (Carpe Diem, 16/44.1 FLAC)
“The journey of love” is a marvelous exploration of love through the ages, from multiple cultures and times. The whole album is a joyous wonder, but the opening track (“Fresh Rose”) of a traditional song from the 1500s is an invitation to join in joy and unbounded hope. The company of players is feeling it, and you do too. When you’re hearing every string pluck in the strums and the voices comes together into something much larger than the sum of its parts, you’ll be glad you accepted that invitation.

L’Amor, from “Bella Terra” by Arianno Savall (Alia Vox, 16/44.1 FLAC)
If “Rosa fresca” makes you fall in love with Arianna Savall singing about love, you’ll want to seek out her “Bella Terra” album. An accomplished harpist and vocalist, Savall is at her best when she brings both together: voice and instrument are one, and evoke marvelous sound and emotional resonances in each other.

Stuck In A Moment You Can’t Get Out Of, from “Open Your Ears” by The Persuasians (Chesky, Binaural 24/96 FLAC)
One last gem from Chesky. There is a profound difference to listening to a recording of a group of people sing, and being with a group of people that are singing. This is another recording that (at least for me), when you cross some magical threshold of transparency, the people become real.


Background and Expectations

I can’t recall being more excited and impatient as I have been for the Chord Blu2. The presentation materials from 2017 CES launch were a tour de force, and it was clear that the Blu2 could potentially represent a long sought after but almost never achieved audio end state. When I purchased (and was blown away by) my DAVE mid 2017, I could literally only imagine where the Blu could take something that was already well beyond what I thought was possible in music reproduction. I preordered and paid for mine in May (my first dedicated CD player purchase since I got my Nakamichi OMS-5A in 1984!), and proceeded to wait through countless delays until I received my Blu2 six months later. As impossibly high as my expectations were, the Blu2 has blown them away in every way.

First some background for those that are not familiar with the Blu2. It is a CD transport with a built in digital interpolation and upscaling filter (what the designer Rob Watts calls mScaler) that operates at an effective one million taps (vs ~25k taps for Mojo, ~50k taps for Hugo2, and ~150k taps for DAVE). According to Rob, in the 80’s he calculated that you needed ~1M taps to be able to reconstruct the original analog signal from a 44kHz digital signal to the limits of what is perceptible. At the time, that was an impossible objective (taps were measured in 10’s, not millions). As time and technology has progressed, the Blu2 now has the compute capacity to execute a 1M tap interpolation filter in real time.

To give you a sense of how insane insane a 1M tap filter is, with the Blu2, the value for the audio at any given instant in time is calculated from all the data in a 1.4 second window around that instant in time (backward and forward). That level of compute is beyond crazy, but it is why Rob uses advanced FPGAs in his DACs that include hundreds of digital signal processors running at the same time.

So how the heck can a sound 1/2 a second in the future or from the past be impacting what I hear right now? That’s impossible, right? The idea is that when the original analog sound was digitized, the digitization process actually took that analog signal and smeared it out over that time window (forward and back in digital time). The original signal is still there, but you have to apply incredible compute to extract it and use it to interpolate the original analog signal. That is what the mScaler is doing: reconstructing the original analog signal based on the math of how analog signals are transformed when digitized. The more taps you have in your interpolation filter, the closer you get to the original analog signal.

The main impact of this is in the precise timing of when sounds start and stop. The unbelievable performance of the WTA filter in the Chord DACs is what (in large part) contributes to the phenomenal sound stage and resolution and sense of physicality you get from these DACs. The mScaler (in theory) represents an end game where the filter reconstructs the original analog signal to the limit of what is humanly perceptible for any given piece of digital content, in this case, all from a lowly traditional CD.

So why the heck would one buy a $10k CD player in 2017, and why pick a CD player of all things to be the first product with a breakthrough technology like the mScaler? The Blu2 just happens to be the product that was first in the queue when Rob finished his next generation WTA filter on the next generation FPGAs. After doing the work to get to a 500k tap WTA filter, the improvement he heard was so significant that he doubled down and did the hard work of pushing it to 1M taps. Since the transformation was so significant, he then spent 3-4 months adding USB support to the Blu so more people could take advantage of the mScaler.

The Blu2 has a cd transport (Phillips CD Pro 2 mechanism), but it can also accept USB digital input (up to 768kHz) and digital BNC coax (up to 384kHz) as input, and put that digital signal through the same mScaler filter. Whatever the digital source, once the mScaler has upsampled the digital signal (up to 705kHz or 768kHz, or 16x) it outputs the upscaled digital signal to your external DAC. The Blu2 has dual BNC coax outputs (up to 768kHz, preferred for DAVE and Hugo2), as well as a traditional coax digital output (up to 384kHz) and dual data AES output (up to 192kHz).

Special to the advanced Chord DACs is the ability to use dual digital coax, to support 704-768kHz (16x) signals. The Chord DAVE was designed 3 years ago anticipating the advent of the mScaler (yes Rob is playing a very long game). It has dual coax inputs that accept up to 768kHz signals. The recently released Chord Hugo2 has a 3.5mm dual coax connector that can accept the sample inputs. When you have dual coax connected from the Blu2 to the Chord DAVE or Chord Hugo2, both DACs autodetect that there is a dual coax connection and switch into a special mode where they use both coax inputs simultaneously.

When you connect to the coax inputs on the DAVE or Hugo2, you bypass the 1st stage of the WTA filter in the DAVE and in the Hugo2. These is the stage that does the heavy lifting of applying the taps to interpolate and reconstruct the original signal. The DAVE and Hugo2 then have the 2nd stage (volume control, cross fade, etc) and the digital to analog output stage. Connecting the Blu2 to these DACs effectively turns your DAVE into a 1M tap DAC (vs ~150k taps) and your Hugo2 into a 1M tap DAC (vs ~50k taps)

Net net: when you run a Blu with DAVE and Hugo2, you have the identical 1M taps. The main difference between the BluDAVE and BluHugo2 in the higher quality and more powerful output stage of the DAVE, better isolation on inputs (I believe) on the DAVE, better power supplies on the DAVE, more filter options on the Hugo2, 2 dual digital out options on the DAVE, etc.

For giggles, the DAVE has two different dual digital outputs. You can actually connect these to a Hugo2(!). When you have a Blu connected to a DAVE, the Blu signal is passed through to the dual digital outs on the DAVE. That means in theory you can run a BluDAVE and two BluHugo2’s simultaneously (woah...how cool is that?). Alas, not as cool as it may seem. According to Rob, the DX outputs of the DAVE are not galvanically isolated. That means that BluHugo2 will sound better than BluDaveHugo2, by how much highly dependent on your setup (in my setup, this was quite a bit)

For those not following at home, Rob has announced that he is working on a digital amp that takes the final digital to analog stage of his DACs and ups the output power to be able to drive traditional speakers. The first is targeted to be 20W, with higher power units in the future. Presumably a future digital amp would take dual coax inputs, and handle the final digital to analog output stage with a higher output power (20W vs 1W with Hugo2 and 2W with DAVE). He has also announced that he is working on an analog to digital convertor (called Davina) that uses the same mScaler technology to optimize the digitization stage and eliminate the artifacts/signal loss/aliasing that is common to traditional ADCs. The combination of theoretically perfect analog to digital conversion (Davina) and theoretically perfect digital to analog conversion (BluDAVE) will be an opportunity to close the loop and validate the theory, and address any gaps between reality and theory. Incredibly exciting stuff.

Presumably, next would be a digital crossover, effectively connecting a digital amp to each driver in a speaker to eliminate transparency loss from the speaker cross over network, but nothing announced on that yet. A digital cross over would (in theory) be a perfect opportunity to do any transducer correction or room correction, esp. if you have a Davina and BluDAVE in the mix (again, all conjecture on my part...nothing has been announced in these areas, but Rob clearly has life long mission that he has been systematically and effectively executing against).

For now, when using a Blu2, I think of the DAVE as a 2W digital amp and the Hugo2 as a 1W digital amp.

So based on available information and my experience with Mojo vs Hugo2 vs DAVE, going in I would expect BluDave > BluHugo2 (although not by much), and that both would be >> Dave (by a lot), with the Dave already >> Hugo2 (by a lot).

Spoiler alert: I was right

Also my expectation bias going in for the Blu2 CD is that it is a novelty that I wish I didn’t have to pay for and not something I would use (I already have all my music ripped, and streaming from a Roon core to a Sonore Sonicoriber SE running Roon Bridge to USB, to my DAC).

Spoiler alert: I was not only wrong, but this represents the second time in the last couple months my audiophile world has been completely and utterly turned upside down.


First Impressions

After 6 months of waiting. my Blu2 arrived while I was overseas on a business trip (arg!). Coming home. I don’t know if it was the 28 hours of travel or the Blu2, but after quickly wiring in the Blu2, Nusrat Fateh Ali Kahn lived again, and he was performing live in my living room. I never thought in my life that I’d hear the man like this. Wow. Truly a blessing to be able to experience this.

At a pragmatic level, the magic that DAVE brings to vocals and stringed instruments, BluDAVE brings to woodwinds and horns. Having not had a lot of first hand experience with these instruments, I had no idea how much depth and subtly was hiding there.

More broadly as a holistic experience, BluDAVE is by far the most artful music reproduction I have ever heard, and even exceeds many of my live music experiences. To explain, I believe that every performance has artistic merit (art being defined as the capture and conveyance of some sort of emotional truth or idea). The performer is working to convey something, the audience is working to receive it, and the engineer is working to capture it. If a reproduction chain is able to reproduce that, even if poorly captured, it is akin to a time machine and transporter rolled into one. It is very rare that I don't enjoy listening to some new piece of music and finding that artistic intent. It may not be for me (so I may not go back to it if I don't care for it), but I appreciate and celebrate what is there, and that it has meaning for other people. I learn as much about myself from things I find resonances with as from things where I don't (and often more from what I don't care for). I also learn more about what matters to other people who resonate more with that sort of thing.

In the case of Nusrat Fateh Ali Khan, listening to that performance with the Blu2 was the first time I was able to completely feel like I was in the room with those musicians and that audience (vs getting afterimages and hints) and got completely swept away. Incredible experience. Shifting to some Coltrane, it was scary real to hear the man be so alive and present.

Shifting to BluHugo2, preliminary feedback is "blissful", "infinite air", "never heard that before", "really evolves the listening experience", "wow you can really separates the headphone wheat from the chaff now”. Incredible stuff.

However, right off the bat we found surprising sensitivity to details/mechanics of the BNC connection between the Blu2 and the DAVE/Hugo, which made more systematic comparisons more difficult. After iterating through N permutations of 3 sets of cables, ferrites, Blu2, DAVE, Hugo2, headphones, Omegas direct, and Benchmark/B&W combos, some patterns started to emerge (wow, I've never heard the B&Ws sound so good!) but also some head scratchers. There is work to do here to get to a stable optimal configuration, and I’ll share our experiences in that journey a bit later on. But first, let’s start with the music.


BluDave vs DAVE

So double clicking down, what does the Blu2 do for the DAVE? BluDAVE gives one an almost superhuman ability to focus on individual performers and the subtlety and nuance of each performance (snare across the drum, subtle bending of strings, the dynamics of a strum, the pluck of a finger pick, etc.) while being able to hear the performance as a whole at the same time. It is a surreal experience for reproduced music, and the best I can describe it is like the feeling when you’re at a concert, and you focus your attention on the bass player (or whomever) and really get a sense of what they’re bringing to their individual performance, while at the same time hearing all the musicians act and react to each other on stage.

In particular, percussion (which was already spectacular with the DAVE), becomes a vivid and present dance with the BluDAVE. For vocals (another DAVE strength), the BluDAVE captures (remarkably) even more nuance and expression…when you close your eyes, it is not a challenge to imagine how the singer’s facial expression and body posture and movements must have looked like during the recording session. The sense of intimacy and presence that the DAVE has (which I already thought was beyond what was achievable in music reproduction) is taken to a completely next level. Wow.

Where previously I characterize the soundstage with DAVE and Hugo2 and Mojo by number of “zones”, with the BluDAVE the soundstage is now effectively continuous (infinite zones). On the best recordings, it is almost holographic (including depth, and to a lesser extent, height) The new continuous soundstage makes it remarkably natural to place a singer or instrument in space, and even (for some recordings) to get a vivid sense of the surrounding room they were recorded in(!) For choral pieces or ensemble pieces, the effect is particularly vivid and immersive: hearing the different rows of a choir and the different heights of the singers is unexpected WOW moment, as is the clarity and vividness of each voice. When the vivid details blend into a seamless whole, the sense of the physical presence of the performers and being part of the performance is glorious. I’ve gone from listening to choral music <2% of the time, to >50% of the time. Completely magical and revelatory.

As pieces get more complex, the more effortless the chain becomes. Listening to some of these more complex pieces (orchestral, etc) with BluDAVE is a revelation: there is no blurring or collapsing of the stage and performers. All that magic from the more intimate pieces where DAVE is world class persists with even the most complex pieces I throw at it. Being able to immerse myself into the layers and complexity and still be swept away by the nuance of the individual performers in an orchestra is a stunning experience. There is so much more to these performances to cherish and enjoy. For a modest orchestra, you can distinguish the individual players and how they’re arrayed around the conductor. For very large orchestras, there are hints of the individual players in the best recordings, which gives me hope that with better recordings and reproduction, there is so much more detail and reality to be revealed.

As I listened more to BluDAVE, it became clear that it has the power to shine the light of a 100 suns on everything in the reproduction chain: content, mixing, speakers, headphones, etc). Pieces that I thought had no upper bound (better the equipment the more they revealed) all of a sudden hit a wall and you could hear the limits of the recording very clearly. While my B&W/Benchmark chain was recreating sounds at a level I had never heard before, it was clear that they were the limiting pieces in the chain. Even my Sennheiser HD-800’s were clearly topped out, and I had to do all my critical evaluation of the BluDAVE and BluHugo2 driving my Omega Super Alnico Monitors direct. Very humbling experience to so unambiguously hear the limitations in the rest of your chain and content, but also exciting because it is so clear when you’ve changed something for the better. These are not subtle audio queues that different people hear and interpret differently; the truth is laid bare by the bright light of BluDAVE.


BluDAVE vs BluHugo2

As a reminder, when connected to the Blu2 I think of the Hugo2 as a 1W digital amp, and the Dave as a 2W digital amp. In addition to the output power difference, the DAVE has a 20 element pulse array digital to analog stage, vs a 10 element array for the Hugo2. DAVE also has some advantages in input/output management, etc. All of the interpolation magic is being handled by the mScaler in the Blu2. So the $8000 question: how does a 1M tap BluDAVE compare to a 1M tap BluHugo2, and will I be swapping out my DAVE for a Hugo2?

This is actually a very difficult question to answer with the equipment I have at hand. In practice, I'm finding the Blu2 to starkly reveal scaling limits in content and equipment and transducers that I never knew were there. Fascinating, and remarkably non-subtle...I haven't experienced this level of starkness and obviousness in audio performance ceilings before. If anything in your chain has a limit, the Blu2 will shine a searing spotlight on it.

From my DAVE vs Hugo2 tests, I know my Sennheiser HD800’s are clearly (and significantly) differentiated between the two, but add Blu2 to the mix and my Sennheisers are the clear performance bottleneck in the chain. That forced me to use direct connection to my Omega SAMs for my evaluation, and has started me on a separate quest to find headphones that can scale better with BluDAVE (still in process).

Using the Omega SAMs connected direct (at a reduced volume so as to not push Hugo2 past its limits), qualitatively, I would say if Mojo is an overall 4 and Hugo2 is an overall 6 and DAVE is an overall 10 (using the scale from my Mojo vs Hugo2 vs DAVE review), then BluDAVE is 40, and BluHugo2 is maybe ~25.

Although not a fair comparison, I also compared the BluHugo2 vs the BluDAVE with the Blu set to 1M/500k/250k taps via the filter switch on the back of the Blu2. To my ear, the BluHugo2 is qualitatively just below the performance of the BluDAVE at the 500k tap setting on the Blu2 (medium). As an other qualitative impression, I’d put the Hugo2 roughly 1/3rd of the way between a Mojo and a DAVE, and a BluHugo2 roughly 1/3rd to 1/2 of the way between a DAVE and BluDAVE.

That makes the BluHugo2 pretty damn good! Any Hugo2 owner should be looking for an opportunity to hook up to a Blu2 and hear what is possible, but be open to the fact that your content and digital chain and your headphones will likely be masking what the BluHugo2 is really capable of.

The more I think about it and the more I play with it, the dual coax input on the Hugo2 is a surprisingly clever and remarkably generous addition to the Hugo2. As mScaler gets more prevalent and accessible, the availability of the dual coax input on the Hugo2 is a wonderful way to future proof your Hugo2, while taking as little space as possible so the product can stay portable.

In addition, it makes the Hugo2 much more interesting as a digital preamp for more traditional digital audio. Each of the digital inputs on the coax can be fed independent digital signals from upstream in your chain (up to 384kHz signal each). So if you already have an advanced CD transport or some other digital source, you can wire up to 2 coax digital sources into the Hugo2 and connect a traditional optical digital source to the Hugo2. You can then switch between the 2 coax digital sources, the optical source, and the USB digital source either on the Hugo2 itself or (more importantly) the Hugo2 remote (as an aside, the Hugo2 remote is an absolute game changer...Hugo2 is a world class desktop product, that you just happen to be able to disconnect and turn into a portable).

All this makes the Hugo2 one hell of a desktop digital preamp (with the exception of the DAVE, probably the finest one available). If you have a (literal) end game digital source like the Blu2 (or future mScaler products), you can wire that in, with USB and optical inputs for legacy connectivity. If you have traditional high end digital sources, you can wire up to two of them via the dual coax, and still have optical and USB available.

The only notable gap I see with the Hugo2 as a digital preamp is that it doesn't have a dual coax digital out. That constrains the Hugo2 to be used with analog out only. One hopes that when the digital amps do become available, the Blu2 will be able to connect to them directly, but we’ll all have to (impatiently) wait and see.


So How Did a CD Player Turn My World Upside Down in 2017?

Initially, the CD transport on the Blu2 was at best a curiosity and conversation starter with my audiophile buddies (“Hey, I paid $10k for a new CD player!”). Honestly, I was expecting to play a couple CDs to see what’s what, write a couple pithy sentences about how “Yeah, sounds like the ripped digital tracks, bits are bits, yada yada” then get back to the usual digital tweaking and swapping equipment in and out of the chain to figure out the new toys.

When I finally gave the CD of the Blu2 a listen (direct to Omega Super Alnico Monitors). I was absolutely stunned by the miraculous sounds I heard, even compared to what was already the best I had ever heard (or hope to ever hear) through the USB interface to the Blu. If obsessing over the digital chain can even approximate what I experienced via the CD mechanism on the Blu, I now understand why so many of us invest so much energy, funds, and passion in obsessively optimizing their digital servers and chain. My apologies for every quizzical look and eye roll I may have had in the past; I now understand.

Arnesen's "Magnificat" from 2L is one of my favorite recordings ever, and I have listened to my favorite track many hundreds of times. Via the USB interface to the Blu, it was by far the best I had ever heard (absolutely stunning, and an amazing improvement over even the DAVE). Completely unexpectedly, listening via regular old CD of that track was one of the most emotional and true musical experiences of my entire life (when multiple normally reserved people are simultaneously exclaiming "Oh My screwing God!” during a quiet listening session, you've crossed into a new place). It was one of the most beautiful things I had ever heard, live or recorded, and I literally had tears running down both cheeks by the end of it. Transformational experience.

With Chesky binaural recordings direct from CD, sound stage is at least 270 degrees from listening position, extending well behind me. With binaural recordings and BluDAVE driving the Omegas, I’m experiencing by far the best surround sound I’ve ever heard (which makes sense if the speakers are precisely recreating the recorded sound stage…headphone like binaural experience from speakers…wow!) Listening to Paquito d’Rivera direct from binaural CD redefines a big band experience for me. Absolutely pick your jaw up off the floor magical.

I should clarify that even though the experience was magical and transcendent, I don't believe there is anything magical about CDs or the CD interface (I'm a big believer that bits are bits). The magic is in the Blu itself. With the CD interface, I can fully hear what a remarkable impact the Blu2 can have. Clearly, there are things in my digital chain that are masking or hampering what the Blu2 can do. For me, the Blu2 CD interface sets the benchmark for what my digital chain should be able to do, and how big the gap is that I need to close with the rest of my digital chain (and when I first listened to the CD player, that gap was HUGE) When my digital chain sounds as good as CD direct on the Blu2, it will finally be good enough.

It took me a couple days to recover from this first experience with CD direct to BluDAVE, but my audiophile world got turned upside down; so many assumptions and intuitions no longer applied. Humbled but excited, and more thoughtful and thorough about investigating various practical permutations of kit, but for now, what a joyful time to be alive, to be able to experience things like this.


Cables/Ferrites and Chasing RF Ghosts

So time to chase this down: how the heck can a lowly CD be so glorious, when my modest digital chain fell short?

I have mentioned already the a surprising sensitivity of system performance to digital connections (USB and BNC) in my system. This was not subtle stuff, but more at a “what the hell is going?” level. Even when we were diving into the miracle that was BluDAVE from CD, we had one or two What moments that were due to the USB cable still being plugged into the Blu. Even playing from CD, disconnecting my USB cable from Blu resulted in a very significant improvement in soundstage, a much sweeter and more relaxed presence, the sound stage expanding back to essentially holographic, and (in the case of Magnificat) choral vocals move from a group shimmer to a girls choir with actual individual girls singing their hearts out. High soaring sopranos become something you fly with, rather than waiting for that break.

Overall, the impact from CD with USB disconnected is just glorious. Emotional engagement jumps at least 5x on Magnificat. To my mind, it is as if some sort of phase transition has happened, and my brain is perceiving the sound on the other side of some threshold to reality. What the heck is happening? How can I get to the other side of that phase transition all the time? (it is addictive as hell)

But wait, aren’t bits bits? Is all I’ve learned about electrical engineering and digital compute over the past 40 years out the window? What the heck is going on?

Once past the euphoria and “I can’t screwing believe this” reaction to the CD sound, time for rationality to return. In digital transmission, if you lose bits, it will result in horrible digital noises/clicks/pops, not comparatively subtle changes in sonic presentation and detail. My challenges in my digital chain were not about losing or dropping bits, but parasitic RF noise from the digital chain degrading the performance of the sensitive digital to analog stages in the DAC. While digital processing may be essentially immune to RF noise from the digital chain (parasitic RF noise is different than noise or signal loss in the digital signal!), the digital to analog and analog sections are not.

Back in my graduate school days, my PhD research involved measuring ultra low level signals representing a very small handful of electrons in nanoscale devices. I learned the hard way (and over many many months of chasing RF ghosts), that if you have a Faraday cage, don’t run a wire into it. Is that what was happening for me now?

The magic of the Chord effect is remarkable but fragile; I’m finding it takes precious little to kill that holographic illusion. Chord DACs have tremendous engineering invested in noise management, power management, and isolation. When using the built in CD with the Blu2, you are basically eliminating the external noise vectors through the digital chain. When you connect the Blu2 to the outside world via USB, those vectors return.

So details matter, and everyone’s experience in their setup will be different and unique. Here is my experience and my learnings, which may or may not map to your setup or experience, but hopefully there is value in the sharing.

Let’s start with the USB cables, and sort out why it was having such a profound impact on what we were hearing. Here are the details on what we iterated through:

• Pangea Audio 1.5m USB cable (PCOCC & 4% silver, $35) - This was the cable I was using when I heard the profound difference between CD and USB
• Stock USB cable bundled with Blu2 ($free)
• Tripp Lite 2m USB cable with 2 built in Ferrite Chokes (U023-006) ($6.53)

In addition, based on posts on Head-Fi (thanks @Jawed), I also purchased 40 Topnisus ferrites to play with (https://smile.amazon.com/gp/product/B01E6PLXXC)

During these initial USB tests, I was using the stock Blu2 BNC cables to connect the Blu2 to the DAVE (no ferrites, etc)

So connecting the various USB cables to BluDAVE, here are the results from my listening tests:

Stock Blu2 USB cable >>>> Pangea USB cable (by HUGE amount)
Tripp Lite > Stock Blu2 USB cable (a modest amount, perhaps because of the built in ferrites on the Tripp Lite)
CD direct > Tripp Lite (a modest amount, mainly in refinement)

So time to start adding ferrites to the cable. I focused on trying to improve the Tripp Lite cable, since that was closest to CD direct. After adding 10 ferrites to the Tripp Lite (on the Blu2 end), there was still a gap with CD direct, but it was clearly better than where I started. When I got up to 20 ferrites, quality was very close to CD direct. After getting to 30, very close to what I heard with 20 ferrites, but with perhaps a VERY small improvement from 20 ferrites. In pushing things to 40 ferrites, I couldn’t detect a change from 30.

At this point I found CD direct to be slightly better than the ferrite-loaded Tripp Lite cable (more space, and slightly better imaging), but very close. I hit diminishing returns on ferrites somewhere between 20-30 ferrites, with no downside (other than a deep personal shame for having a USB cable with 40 ferrites to have more ferrites on the cable.

So USB cable really matters (at least having the wrong one in the Pangea) and ferrites make a clear audible difference. What about the dual BNC cables?

Remember that I was hearing a lot of variability and lack of consistency in my initial assessment of cables when my BluDAVE was in my cabinet. I suspect the cables were brushing against power and USB cables, etc. To avoid physical layout issues, I had my BluDave on my coffee table so I could make sure cables aren’t touching anything, and the inconsistency went away.

Here are the BNC cables that I played with:

• Stock Blu2 BNC cables (1m, free)
• Monoprice BNC cables (2m, $2.50 each) https://www.monoprice.com/product?p_id=626
• Canare BNC cables (2m) ($42/pair) https://smile.amazon.com/gp/product/B0010CIW98

With no ferrites on the BNC cables, here are the results from my listening tests:

2m Monoprice > 1m Blu2 stock cables (small but consistently noticeable difference)
2m Canare >? 2m Monoprice (*very* small difference, if any; hard to consistently pick up with all the cable swapping)

My take away: cable length matters more than build, with 2m better than the stock 1m cables, consistent with Rob’s recommendation from his listening tests.

Next, time to bring ferrites to the party. Here are the ferrites I used on my BNC cables:

• Wurth 74271633S 2.5GHz ferrites (preferred) (2x, $7 each) https://www.digikey.com/product-detail/en/wurth-electronics-inc/74271633S/732-1514-ND/1638918
• Wurth 74271131S 1GHz ferrites (8x, $5 each) https://www.digikey.com/product-detail/en/wurth-electronics-inc/74271131S/732-3625-ND/2901120

Rob has recommended the 2.5GHz as preferred (higher impedance in the RF range that matters for noise from the Blu2), but I had a mixed bag of 1GHz and 2.5GHz ferrites for these initial tests.

Given I could not detect a material difference between the cheap Monoprice cables and the Canare cables, I did my ferrite testing on the 2m Monoprice cables.

While playing music, I started to put ferrites on the BNC cables one pair at a time, starting at the DAVE end. I could hear a clear difference after 2 on each cable, with progressively less difference as I added the remain 8 ferrites (total of 5 on each cable).

Comparing the Monoprice 2m cables with 10 ferrites vs bare Canare 2m, Monoprice ferrited cables were the clear winner (not subtle).

So the Blu2 is a vector for digital noise (whether from a digital source connected to the USB input of the Blu2 or internal to the Blu2) to get injected into the DAVE. If you clean up the BNC digital link between the Blu2 and the DAVE, would that also clean up any noise being injected via USB? For this experiment I kept the ferrited-Monoprice-BNC cables connecting the Blu2 to the DAVE, and compared the 2m Tripp Lite USB cable + ferrites with the 2m Pangea USB cable (the really crappy one) with no ferrites. The result? They were very very close (close win for the Tripp Lite USB cable), so the answer seems to be “yes”.

One final experiment. DAVE is supposed to be immune to problems upstream of USB. What the heck is going on here? Taking Blu2 out of the equation and going with USB straight to DAVE, I tested the Tripp Lite USB+ferrite monster vs the stock Chord USB cable (no ferrites) vs my troublesome Pangea USB cable (no ferrites) connected straight to DAVE. To my ear, the Tripp Lite + ferrite cable and bundled stock USB cable were identical, with a VERY slight step down with the Pangea cable. DAVE takes care of business on its USB input. The challenge is USB injecting noise (via the Blu2) into the DAVE via the unisolated digital coax inputs on the DAVE, and the Blu2 injecting noise into the DAVE via those same inputs.

So let’s roll this all up. How does direct CD on the BluDave sound like compared to digital coming through the ferrite USB monster and the ferrite BNC monsters? To my ear, very very close (perhaps the slightest of edges to CD? Hard to say consistently).

Net net on my learnings from this digital tuning:

• Digital coax on the Chord stack (with no galvanic isolation on the Dave DX inputs and outputs) requires RF hygiene. Use reasonable quality 2m 75ohm coax cables (Monoprice is fine for me), add 4-5 of the 2.5GHz ferrites on the DAVE end, and Bob’s your uncle
• Your digital source is a potential source of noise injection into your Blu2 via USB. You’re fine to use a reasonable quality vanilla USB data cable.
• Audiophile USB cables that are trying to optimize signal transmission aren’t helping you when you’re trying to manage parasitic RF noise that is piggybacking on the digital connection (enhanced conductivity at the cost of additional RF noise is not helpful)
• If you like, you can load up the USB cable with 20-30 of the el cheapo ferrites if you really want to go the extra mile.

Net net for me? I just saved $5k on a new digital music streamer with some inexpensive USB and BNC cables, and an embarrassingly large number of ferrites. Thank you internets.

As I identify and address whatever the next big performance bottleneck is in my system, will my digital source become the performance limiter? Perhaps, but I’m delighted to be able to put off worrying about superclocks and ultra linear power supplies and modded network switches for a little while longer.

One last thing. How to do physical cable management once I cram everything back into my cabinet and these embarrassing cables are no longer cleaning laid out and isolated? For giggles, I got one of these https://smile.amazon.com/Kootek-Management-Concealer-Organizer-Reversible/dp/B01GCS77TU and wrapped the beast up. Hides my ferrite shame, and seems to be working for me so far.

Edit 1/21/18:

A quick (but very belated) promised update on Wurth 2.5GHz ferrites vs the 1GHz ferrites in my BluDAVE setup. I ordered a total of 10 of the 2.5GHz ferrites, and I was finally able to compare the two. I was able to hear a very slight but consistent improvement in detail and resolution (VERY slight) with the 2.5GHz ferrites over the 1GHz ferrites. Both were superior to no ferrites in my setup (for this test, Blu2 CD -> DAVE -> direct to Omega Super Alnico Monitors).

Is it worth swapping out 1GHz ferrites if you have them already? Up to you, but these are so (relatively) inexpensive that it is probably worth it for peace of mind, but not because it will alter the experience of the BluDAVE in any fundamental way. If you haven't ordered any ferrites, I recommend starting with the 2.5GHz ones.


Conclusion

The Blu recreates music with a true sense of reality that is fundamentally different than anything I’ve heard before. On the scale of “listening to music” to “experiencing a performance”, the emotional reality of what I’m hearing transcends even experiencing a performance to participating in a work of art.

For the best recordings, the experience of listening through BluDAVE is on the other side of some reality phase transition: my brain is no longer filling in the blanks and extrapolating, I am there with the artists and they are here with me, and I am feeling what they are feeling. The emotional impact of their art can be profound, and it is a gift beyond measure to make their art so profoundly manifest.

I will not be replacing my BluDAVE with a BluHugo2 (I am addicted to the BluDAVE sound), but the BluHugo2 is (remarkably) a huge step above the DAVE. As mScaler technology becomes more mainstream, it is fills me with awe to think these sorts of musical experiences will become available to ever larger audiences. I will also not be upgrading my digital server to something like the Innuos Zenith SE; with RF hygiene things are close enough to CD in my setup that I will be investing my energies in addressing other potential short comings in my system first.

More generally, the Blu2 has highlighted the limits of essentially all my content and equipment. Finding the right combination where any listening tests were not dominated by those limits was incredibly illuminating and humbling. Basically, everything degrades what the Blu2 can produce. You just try to minimize that degradation.

When you have a true ground truth reference in your system, I'm finding that I end up measuring everything else against how much it degrades from that reference. As someone who's ideal of criticism has always been to focus on how much something elevates, it has been a disorienting reorientation for me: eliminate as much as possible to try and approximate the true reference, then add things in to see how much they drag it down. I can't say I'm enjoying this new way of critiquing content and equipment, but it is shocking how clear differences and degradations are (this is non subtle stuff). There is no denying or penciling over the truth that you hear.

We are in early days of this brave new world, so there are some teething pains. A Chord future that depends on dual BNC cables to move around 705/768kHz signals between multiple pieces of high-powered digital kit will need some serious thought for how civilians are going to manage the sensitivity to cable placement and management and RF noise. Based on my experimentation and the reports of others, there is a clear opportunity to bundle cables that are optimized for this environment, and adding galvanic isolation to a future digital amp will also clean things up. Until then, good RF hygiene is required, so swallow your pride and load up on the ferrites.


Coda: The Emergence Of A Brave New World

Normally, I have done critical listening tests with headphones, but my (until now infinitely scalable) Sennheiser HD800’s have clearly topped out with the BluDAVE. The only configuration I have access to that exposes the real performance of BluDAVE is to drive high efficiency single driver Omega Super Alnico Monitors directly from BluDAVE.

To hear what the BluDAVE is capable of, I’ve had to eliminate as much as possible from the reproduction chain. Wow.

Anything between BluDAVE and the transducer degrades what you hear by some amount. Simple things like moving coax cables are audible. Adding one ferrite at a time is audible. Moving a power cord out of the way is audible. Any amplifier (class AB/D/T/tube/whatever) in the chain or speaker crossovers take precious transparency and presence away and is audible. I’ve resisted swapping out speaker cables and power cables for some esoteric $$$$ variety because I fear what my wallet will hear (ignorance is bliss), but I’m certain they will be audible and may be significantly. When Rob says that even the smallest XXX is audible in depth queues, he’s right.

This notion that anything between BluDAVE and the transducer degrades the reality of what you hear was a profound upside the head when I realized it. All my old tricks and nearly all my intuition were out the window. Seeking perfection and truth by stripping away everything but that perfection and truth. It’s enough to spur a mid life crisis.

So what does this new outlook mean for me in practice? We often talk about this or that piece of audio kit being “reference”, but that is in the context of what one is familiar with and that we compare everything else against. How are things better or worse? Same or different? Almost universally we speak of reference as a basis for comparison, to find common ground so we can understand something new in the context of what we know.

In a very first for me, the Blu2 is (for all practical purposes) a true reference: it establishes the ground truth from which everything else takes something away. That is, the Blu2 is a reference for measurement, not just comparison, and represents an ideal that everything else needs to work toward attaining.

Understanding what something is taking away is key to understanding and optimizing your chain, but it is humbling with the stark unassailable clarity about the differences that you hear. At least at the beginning of this new journey, I am hearing 50% to 80% changes (towards the ideal), not the usual 99.84 to 103.89% changes (vs the baseline reference) we endlessly debate about. It impacts everything from electronics to speakers to my room to my emotional mood to the actual music content and performance.

To be 35+ years into the serious audiophile thing (and even longer into the life thing) and to rediscover Beginners Mind in a ground truth is a wondrous and wonderful and profoundly humbling thing. I'm very grateful for the privilege and good fortune to have a piece of that mountain top in my living room. I am also exceedingly happy to celebrate the culmination of a lifetime’s work for Rob, who has been systematically working toward attainment of this ideal for over 30 years. Bravo sir.

For all this awesome, the mScaler technology in the Blu2 represents a true (truth?) end game for only one piece (albeit an incredibly important piece) of the music capture/transmission/reproduction chain. I can’t wait for hearing an absolute reference for digital music capture (Davina), the ability to drive more impactful transducers (digital amps), and an absolute reference for multi-driver and room correction (digital cross over), and for all these magical things to be tied together into a closed loop so that reality can be vividly and holographically reconstructed. It may take another 5-10 years, but we will hear reality fully captured and recreated in our lifetime, and the mScaler technology in the Blu2 is profound first pillar and foundation for the rest of that journey.