When you think of DAC
technology, is Chord Electronics the first company that comes to mind? Well if
you read my
review of the Chord QBD76 it might well be. This exquisitely designed
component, derived from the extraordinary Red Reference CD Player, performed to
a remarkably high standard in my 2009 test. The conclusion: "I can assure you
the Chord is fully up to the challenge of getting the best out of Red Book and
Bluetooth, and exceptional performance from a true high resolution source."
So when the opportunity came to see what Chord has been up to more recently, I jumped at it. I was given the choice of the latest iteration of the QBD76 (now the QBD76 HDSD) or a much less expensive derivative, the QuteHD. I picked the latter since it has not been reviewed yet in North America, and it is likely to sell in much greater numbers.
Let us take a closer look at the secret sauce. Chord does not buy its DAC chips off the peg. Instead it implements conversion on its own custom Xilinx Field Programmable Gate Array (FPGA) chips. Not just conversion – digital receivers for each input, automatic input switching, clocking, Isochronous USB timing and digital Phase Lock Looping, WTA interpolation filtering, DSD over USB support in addition to Chord's own Pulse Array digital to analog conversion.
WTA stands for Watts (after Chord's Robert Watts) Transient Aligned. The WTA interpolation filtering is a digital processing algorithm developed at Chord to preserve all the important transient information in the original signal while removing all the spurious information that signal contains. In Chord's highly successful DAC64, the predecessor to the QBD76, they used a tap length of 1024 taps to implement the WTA filter, while the QBD76 extended this to an amazing 18,432 taps using 18 separate DSP cores, allowing a greater sophistication in the implementation with resulting audible benefits. The Qute HD uses 10 parallel DSP custom-designed gate level cores to give a third-generation WTA filter of 10,240 taps.
The Pulse Array DAC in the QuteHD is a fifth generation implementation of Watt's delta/sigma DAC, implemented in a simpler fashion than earlier Pulse Array DACs using just 4 elements. Chord claim very high resolution of low level signals, very low sensitivity to jitter, no noise floor modulation, zero anharmonic distortion harmonics and very low harmonic distortion. It also directly handles the DSD signal without the need to convert it to multi-bit.
Chord includes a separate FPGA chip to handle
asynchronous USB communication and to isolate the DAC clocks from the computer.
Each sample rate clock is generated discretely using highly accurate crystal
oscillators for optimum performance and ultra-low jitter performance.
So what's all this about DSD – you can't pass DSD across the S/PDIF inputs can you? No, but the QuteHD, along with big brother QBD76 HDSD and the recently reviewed EMM Labs DAC2X are among the first DACs to accept DSD over USB using the new DoP 1.0 protocol. This allows you replay DSD downloads from your computer in a bit perfect mechanism whereby the DSD stream is actually wrapped up into a high resolution PCM carrier for transmission over USB. Note that the signal is not being converted to PCM and converted back inside the DAC – PCM just supplies a wrapper which is attached before transmission and discarded upon arrival. You'll need a compatible music player on your Mac or PC – I used JRiver Media Centre 17 on a Dell notebook, and then you follow the detailed instructions from Chord as to which settings to make (kernel streaming for native playback and DSD support) and which drivers to load. The Chord will then appear as "Chord Asych USB 44.1kHz to 192kHz" in the soundcard.
It is great news that the QuteHD supports DSD in
this fashion, and is likely the least expensive component currently available
that can do so, but it is also capable of accepting PCM signals of up to
192kHz/24-bits over any of its inputs, and 384kHz/32-bits on its S/PDIF input.
That should keep everyone happy for quite a while.
I started by using the DAC to bypass the output stage of a Meridian G08 CD player, which emits an 88.2kHz/16bit (upsampled) stream to the QuteHD over a TosLink S/PDIF connection. The unbalanced analog output from the QuteHD fed the EMM Labs Pre2 preamplifier and from there to the ModWright KWA150SE and YG Carmel speakers. I compared this sound to the balanced output of the G08 going directly into the Pre2 and also the reference EMM Labs XDS1's balanced analog output into the Pre2. I achieved precise level matching using white noise measurements and set identical CDs to play in both CD players. Across a wide range of material the ranking order was always XDS1 first, then the QuteHD and then the Meridian's analog output. To outperform the Meridian's inboard DAC is a very significant achievement, since very few DACs that have passed through my hands have achieved this. But what is more impressive is that the G08/QuteHD combo was actually nipping of the heels of the reference XDS1, despite the advantage a balanced configuration might offer. AB testing hardly revealed any differences. To really tell the difference I had to listen to each option for an extended time, to let myself relax deeply into the music and see how the music affected me in a very subjective fashion.
Where the XDS1 has a small edge is in the size
and stability of the image and the blackness of the background. In terms of
resolution, orchestral color, dynamics and absence of digital fatigue I simply
could not tell them apart. This is an absolutely stunning result for the QuteHD,
and it also speaks highly of the ability of the G08 to extract all the bits from
the disc. Meridian claims a 10 times improvement in the error correcting ability
for its CD/DVD-ROM drive over standard CD drive units for this unit. That, and
very careful attention to the power supply, may be the key to providing a good
stream, but TosLink is not generally regarded as a jitter free delivery
mechanism, so either the QuteHD's proprietary RAM buffering must be doing a
superb job of de-jittering the signal or its DAC section must be unusually
impervious to jitter components. In short the sound through the QuteHD is
extremely dynamic and detailed, with accurate color, fast transient response and
strong imaging, a full bandwidth sound competitive with top flight CD players
from Esoteric, dCS, Accuphase, Meridian and EMM Labs. It's not a sound optimized
towards one type of music. It seems equally happy on rock, folk, jazz, pop and
classical music of every scale. I simply couldn't find a CD that was too
demanding for it, that embarrassed it next to the reference.
That it performs so well with CDs is great to know, but I suspect most people will be suing the QuteHD through its USB input, for streaming music files from their computers. I used a simple Dell notebook computer with a large database of music ripped using a variety of formats and resolutions, including 192kHz/24-bit, 96kHz/24-bit and DSD. Many DACs can handle the very high rez 192kHz/24-bit files, but very few can handle the DSD files, for which you need specific media players' such as the JRiver Media Centre 17 that I used. The high end EMM Labs DAC2X ($15,500) has similar capabilities and with its memory fresh in mind I can tell you how impressive I found the QuteHD. For direct comparison I played the same source material on disc wherever possible through the XDS1.
Again I'm surprised just how close the DSD stream through the QuteHD comes to the XDS1 playing the same SACD and the same file playing through the DAC2X. Yes there are differences, and they are a little easier to discern than the Red Book comparison, but still you have to strain to hear them. The XDS1 beats the QuteHD in terms of its larger and more relaxed image which makes the music flow more naturally and convincingly. The DAC2X takes the DSD stream up another very small notch, but you've got to look at the price tag and the size of the box. Right up against the best there is, this $1795 DAC goes head to head and matches it on most scores, trailing only a little on dimensionality and ease. I never would have thought it.