Tuesday, April 13, 2021

Astell&Kern USB-C Dual DAC Cable


Chances are that you use your notebook, tablet, or mobile phone to play music, especially through a streaming service like Tidal or Spotify. Sound quality is typically poor or mediocre. Integrated audio chips work in noisy electrical environments, and usually lack the necessary power to drive high-quality headphones. 

Astell&Kern have released a USB-C DAC / headphone amp that provides an instant boost to your sound quality and lets you use your 3.5mm wired equipment with devices that lack a headphone jack, like some of the new mobile phones.


The USB-C Dual DAC Cable ("Dual DAC") is based on twin Cirrus Logic CS43198 MasterHIFI Digital-to-Analog Converters. The CS43198 is a Delta-Sigma oversampling DAC that supports up to 384 kHz sampling rate / 32-bit resolution for PCM and DSD 256. 

As expected from an Astell&Kern product, the Dual DAC is finished to a high standard. The compact metal Zinc alloy body (it is no bigger than a thumb-drive at 50 mm x 17 mm x 10.3mm !) houses an integrated circuit with bespoke designed capacitors and an optimised audio circuit to minimise power fluctuations and provide premium sound quality. 

Astell&Kern claims that the analog amplifier is powerful enough to drive a variety of high impedance headphones with a 2V rms output level (condition no load). Output impedance is suitably low at 2 ohms, which should ensure lower distortion into low impedance headphones. 

The fixed cable is a durable 4-core cable made out of a core of Technora aramid fiber, with a layer of thick silver-plated copper wrapped around it, followed by a further layer of copper wire in a spiral arrangement. The tastefully angled housing is carried over to the matching USB-C connector. A single LED indicates operation, while volume is controlled through the device it is paired with. 


The Dual DAC worked without any issue with a variety of devices I tried - a Samsung Galaxy S10+ mobile phone, a Windows 10 notebook, and a 2020 Macbook Pro notebook. The bulk of my listening was done on the Samsung, playing music either through the Tidal or USB Audio Player Pro app. Power-draw was modest and I did not notice any adverse impact on battery life. Sadly, the Dual DAC is incompatible with iOS devices due to current limitations through their ports. Both high-resolution PCM and DSD files played without any issue.

The USB-C connector is quite large and may not fit properly through your mobile phone case. My case cut-outs were not big enough and I had to remove my phone case to plug in the Dual DAC. I am in two minds about the fixed lead. I like the idea of a fixed cable, but it is quite short and in the case of my Windows 10 notebook, the USB ports are located on the side of the screen, which left the Dual DAC suspended in the air.

Sound Quality

The Dual DAC provided a significant uplift in sound quality and drive capability, with the improvements most noticeable on difficult to drive headphones. I tried it with a variety of IEMs, as well as two headphones - a Beyer DT880 (250 ohm version) and an E-MU Teak. Most of my listening was done on the E-MU for reasons explained below.

The most striking improvement was in the reproduction of low-frequencies. The Dual DAC added a tight punchiness that went deep. Vocals gained clarity and refinement, adding sweetness and uncovering details that were previously obscured. High-frequencies too gained extension and airiness, giving music and brighter and more illuminated tone. The soundstage opened up, with an increase in dimensionality and the sense of acoustic space in the recording.

Pairing the Dual DAC with IEMs brought improvements in sound quality, but the Dual DAC's strength was in bringing extra current and voltage drive for more difficult to drive headphones (within reason). While the DT880 showed improvements with the Dual DAC, it lacked the dynamic freedom and ease compared to my desktop headphone amps. The E-MU Teak is easier to drive in comparison and was very comfortable with the Dual DAC, even at high levels. Given the compact size of the Dual DAC, this is a reasonable compromise.

I was impressed with the high level of sound quality delivered by the Dual DAC and can highly recommend it to Android phone users who want the best sound quality on the go, or to business travelers that need a high-quality and portable audio rig.


From a pricing standpoint, the Dual DAC is a premium product that carries a corresponding price tag. The competition offers similar products, some at a lower price point with features like balanced drive capability. I think the pricing is fair, and like any Astell&Kern product, you get lasting pride of ownership. 

The Dual DAC will be available in May 2021 at a retail price of S$ 189- Highly Recommended.

You can purchase the Dual DAC from AV One (https://av1group.com.sg), Connect IT, E1 Personal Audio, Headphones.SG, Jaben, Stereo Electronics, and Treoo.com.




Saturday, November 7, 2020

Acrolink Mexcel 7N-PC9900 Power Cord


The 7N-PC9900 is the latest version of Acrolink's flagship power cord, replacing the PC9700. According to Acrolink, the PC9900 is an upgraded version of the PC9700 and features new special shielding technology. 


Visually and reading off the specifications sheet, the PC9900 and PC9700 are near identical twins. The Live and Neutral conductors are the same D.U.C.C. Stressfree 7N wires consisting of 50 strands of 0.32 mm diameter conductors, while the ground is similar except the wires are made from super-anneal 4.5N copper. 

The shield is described as polyurethane enameled 4N copper braid with special shielding technology - carbon fabric sleeves. In comparison, the PC9700 uses the same copper braid combined with semi-conductive carbon tape. 

Otherwise the PC9900 looks and feels the same, with a diameter of 16 mm and identical resistance and capacitance values. 

I no longer had the PC9700 on hand so I could not compare the two models. Instead, I used the 8N-PC8100 as a baseline for comparison instead.

Sound Quality

Acrolink Mexcel users expect the finest levels of resolving power and suppressed noise floor, which the PC9900 delivers in spades. 

The PC9900 has extremely high levels of resolution across the frequency range, with tight and powerful bass lines, and high frequencies that are extended and clean. In typical Mexcel fashion, this is delivered in very quick and focused transients, with a natural decay. Due to the very low noise floor, the PC9900 is almost like delivering a jolt to your system, giving it a sudden boost in contrast and dynamic range. 

Tonally, the PC9900 sounds similar to the PC9700 (based on memory). A quick read of my previous review of the PC9700 provides more insight into the character of both the PC9700 and PC9900. However, the PC9900 offers subtly improved resolving power with a little bit more focus and drive. I noticed that the Mexcel twins differ in how the human voice is presented. While both cables have more sweetness in the midrange compared to other Mexcel models, the PC9900 has a silkier and more fluid delivery. However, this comes at the expense of some snap and presence.

Comparisons to the PC8100 proved interesting. Unlike the PC9700, I would consider both the PC8100 and PC9900 to be on par with each other. The PC9900 is like using a computer monitor with higher resolution. The PC8100 makes do with lower resolution, but with more colour contrast, and a slightly warmer hue. Your choice of poison boils down more to taste. If you like a bolder presentation with more meat and flavour, the PC8100 fits the bill. The PC9900 is perfect for the palate that favours microdetail and a more refined and sophisticated presentation. If you like your Japanese whisky, think of the PC8100 as Nikka, and PC9900 as Yamazaki.


Acrolink Mexcel power cords are one of the finest products in the industry and come with a strong personal recommendation. While they are expensive, the level of performance delivered is very reasonable. I would have hesitated to say this some years ago, but a quick look at audio magazines and websites shows that flagship cables from the competition can even cost multiples of the PC9900 - Highly Recommended.

A big thanks goes out to X-Audio for arranging for the review sample.

Acrolink Mexcel 7N-PC9900 Power Cord
Price : S$ 5,500

1 Jalan Anak Bukit 
#01-01S, Bukit Timah Plaza
Tel : 64662642



Friday, September 18, 2020

AGD Audion Monoblock Power Amplifier


AGD Productions Inc is the new kid on the high-end audio block. The brainchild of Alberto Guerra, AGD Productions Inc produces products that are distinctive and different from the competition.

For one, their amplifiers use their proprietary GaNTube technology. A friend of mine mentioned, "It looks like a tube, lights up like a tube, and sounds like a tube". The photo of the GaNTube below shows that a transistor based circuit housed in a vacuum tube like envelope. From the octal base, to the getter flashing on top, this looks like a typical 6550 or KT88 tube.

The GaNTube™ is a class D circuit, utilising Gallium Nitride MOSFET transistors in lieu of conventional silicon transistors. Gallium Nitride is being touted as the next big thing in semiconductor manufacturing, boasting superior performance in more compact packages. They are superior in terms of power efficiency, thermal stability, RF production and immunity. 

Alberto Guerra enjoyed a long and illustrious career in companies like Infineon and more than knows his way around Gallium Nitride technology, holding ten patents to his name (including two in Gallium Nitride know-how).


The Audion comes in a really big Pelican case. Opening the case reveals the the pair of monoblocks, product literature and a pair of power cords. The amplifiers are compact and light at 2.5 kg each. In fact, the Pelican case feels heavier than the amplifier. 

Finishing is of high quality, with a solid indestructible feel. You can opt for the brushed finish, or a chrome finish for a premium. My review sample came with the brushed finish. The company logo is engraved into the front panel, while all inputs and the power inlet are located at the rear. The excellent speaker binding posts (a pair of WBT Nexgen 5-way posts) are located on the top of the amplifier, behind the GaNTube. If you are using spade terminated speaker cables, this all fits very nicely. However, if you are using banana plug terminations like me, your cables will arch gracefully (like my flexible speaker cables), or suspend your Audion amplifier in mid-air in a worst-case scenario.

The power switch is located directly above the IEC inlet and will be partially blocked by monstrous power plugs that ship with any serious garden hose. Otherwise operation is event-free. The GaNTube glows orange like a vacuum tube except very little heat is produced. I demonstrated this to a visiting audiophile by resting my finger on the GaNTube in the middle of a listening session. No start-up noises or power-down thumps - excellent manners for this house guest. 

The Audion packs plenty of power, delivering 85 WPC into 8 ohms and 170 WPC into 4 ohms. It can deliver more than 30A of current which should be more than enough for most of the speakers out there in the wild. The input impedance of both the RCA and XLR input is 40 kohms (600 ohm inputs can be custom ordered). Noise is an astonishingly low -130db. The GaNTube™ switches at a frequency of 400 kHz.
I tried the Audion with three DACs with digital volume control (the Chord Dave, Totaldac D-1 Six and Antelope Audio Zodiac Platinum DAC). I also tried using a Music First Audio TVC preamp. Although the specifications do not specify the input sensitivity / gain of the Audion, it is definitely quite high. All three DACs were being used between -30db to -20db. In the case of a DAC with digital volume control, that is sufficient attenuation to potentially result in resolution loss. If you are using an active preamp with high amounts of gain, you have been warned ! In fact, this is one of the very few power amplifiers I've used that sound really good driven directly from the source. Save your pennies by skipping the preamp ! Another noteworthy point is that Audion sounds good through both the RCA and XLR input - no worries if your source is single-ended only.

Sound Quality

Let's get this out of the way first - Class D amplifiers get a bad rap from audiophiles. Conventional wisdom is that Class D amplifiers are sterile and lifeless. I have owned and auditioned enough Class D amplifiers to understand their appeal and their strengths. Many years ago, I bought a pair of monoblock amplifiers from a Japanese company called Flying Mole. They are no longer in business, but the product showed great promise. I have also owned a number of Class T amps (i.e. based on the Tripath chip), and amplifiers with both B&O ICEPower and Hypex modules. Each generation of module showed steady improvement, and a number were of high enough quality to challenge traditional amplifier designs.

The Audion need not make any excuses for itself. The sound quality easily surpasses most traditional amplifier designs and can even be considered as a serious challenger to the top amplifiers on the market. 

First up is the bass authority you get from the Audion. Class D amplifiers typically have superb control over your woofers. In some cases, you get a tight bottom-end that seems artificial with a lack of shading or texture. The Audion breathes freely here - as an example, double bass notes flow with timbre and life. The bass has just the right amount of wetness for me, although I did feel that there was a slight midbass emphasis, which resulted in a weightier and warmer tone.

The midrange has an inner glow quality that good single-ended triode amplifiers possess. However, this glow is even-handed and avoids the thick luscious tone that some tube amplifiers aim for. Some equipment smooth over the midrange to portray a more "musical" tone, but the Audion retains plenty of microdetail. 

The Audion's high-frequency performance must have delivered the greatest surprise during my review experience. Even the best class D modules I have heard (with the exception of the Orchard Audio BOSC - a story for another day) subtly reduce the top-end air in the recordings. While they do not by any means sound dull or rolled-off, you could sense a slight reduction in the scale of acoustic space. I always assumed that this was a necessary evil resulting from the low-pass filter required in class D designs to filter out ultrasonic noise. The Audion come through clear and extended. Neither is there any glare or harshness in the reproduction - cymbals crash and bells ring in a clear and extended manner, with a firm but crisp tone. 

Solid state amplifiers excel in staging precision but often cannot match tube amplifiers in dimensionality - the acoustic space around voices and instruments, and the perception of depth and height. The Audion could very well have been of vacuum tube pedigree in this regard, delivering convincing reproductions of each voice and instrument in the recording mix. Marry this with solid state speed and low frequency control, compactness and lack of heat - you truly get the best of both worlds here ! 

Prior to my experience with the Audion, discussions about Class D amplifiers with friends have always been caveated to a degree, e.g. "They deliver a lot of clean power for the price and are very accurate, but you really need a good preamplifier to flesh out the tone and complete the picture.", or "They really deliver bang for the buck, but if you spend a lot more, you can get even higher sonic performance." 

My caveats here are altogether different. Firstly, the high amounts of gain requires some care in matching with preamplifiers and sources. Secondly, the Audion is not affordable although it delivers exceptional sound quality for the price. The price tag puts it out of reach of most audiophiles but quality is never cheap. 

You could also make the argument that the Audion is not neutral. It isn't and to me it was almost certainly a deliberate design choice. Instead, it chose to be musical and delicate, while having the speed, power and control to bring realism to large-scale works. You can now have your cake and eat it ! 


The Audion is a truly revolutionary product. I understand that AGD already has several different GaNTube™ designs in the making, including a higher powered version, and a lower powered one for headamp use. The new modules may be installed in place of the current GaNTube™, which shows that the socketed GaNTube™ is not merely a whimsical fashion choice. 

Keep you eye on AGD, this is a truly special product that will redefine your notions of Class D and solid state technology - Highly Recommended.

This review was made possible with the kind assistance of Horizon Acoustics, sole distributor of AGD Productions Inc in Singapore. 

AGD Audion Monoblock Power Amplifier
Price : SGD 12,800

Horizon Acoustics

1 Pemimpin Drive
#08-11, One Pemipin
Singapore 576151