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

Monday, August 24, 2020

The Quick and Dirty 300B tube shoot-out


The 300B vacuum tube must be one of the most talked-about vacuum tube models, especially in Asia. Critics like to pan it as hyped-up, before introducing their own favourite directly heated triode tube. Others on the other hand revere it as the lighted path to sonic bliss.

The 300B tube was introduced in 1938 by Western Electric to amplify telephone signals. It is a large directly heated triode tube, with a typical power of 8-9 watts for a single-ended design, and about double the power for a push-pull or paralleled design. I recall that it's popularity was at its peak in the 1990s and 2000s, coinciding with the surge in popularity of single-ended triode amplifiers. 

The Shoot-Out

One of my audiophile pals recently bought an Elekit 8600R integrated amplifier and loves it to bits. His set has the works, including upgraded resistors, premium coupling caps (V-Cap CuTF), Lundahl output transformers and a TKD potentiometer. He recently bought a pair of Elrog 300B tubes and I offered to "help" (more like push him down the slippery slope) with some tube rolling activities.

The Elekit 8600R is an affordable 300B integrated tube amplifier, with a single 12AX7 and two 12AU7 tubes used in the input and driver stages. It uses solid state rectification and is available with a variety of upgrade options. The catch ? You have to build it yourself. The circuit is laid out on PCBs, but there are a lot of parts to solder, and some of the solder pads are small and very close together. This is definitely not a kit for a beginner and you should have a bit of soldering experience and good soldering equipment before tackling this. Your reward is a great sounding amplifier at a fraction of the cost of a completed product.

Here is a group picture of our contestants :-

(Clockwise from top left) - Shuguang Treasure 300B-Z, Elrog, Takatsuki, Genalex, Sophia Electric Royal Princess.

As a disclaimer, none of these tubes have considerable time on them, with about 25-50 hours of playtime except for the Sophia Electric which is used and has at least a few hundred hours on them. Some claim that these premium tubes may need about 500 hours of burn-in time to sound their best. Secondly, the logistics and timing of this get-together only permitted us to warm up the tubes for about 10 minutes before playing 3-4 tracks. There were three other participants besides myself (one person left after the Elrog and Takatsuki comparison - he was too deeply traumatised to continue having sold off his Takatsukis during a moment of foolishness !).

Elrog ER-300B

There were reports of unreliability in the early days, but things are said to have improved significantly after Thomas Mayer took over. The Elrog stands tall and proud. The taller than usual height meant that the Elekit tube cage could not fit and had to be removed. 

The Elrog retails for EUR 1,240 per pair including VAT and shipping within Europe. These tubes have a maximum plate voltage of 600V and 40W dissipation ! The re-issue Western Electric 300B in comparison has a maximum plate voltage of 450V.

I really liked this tube. It has a Teutonic precision to it, with very tight and controlled bass and a linear sound throughout the frequency range. Among all the tubes tested, I found it to have the best dynamics and speed. The soundstaging is laidback and the tonality is slightly dark. 

Here are the comments from the other participants :-

"Neutral, dynamic, tight bass, good extension of highs and lows. Suitable for fast music and rock."

"Open sounding. Linear and muscular. Detailed sounding as well."

".... pushed the vocals and focus "in front", towards the listener. The soundstage was more intimate, but may actually be more transparent- it had a precise and narrow focus to the sound made the ANJ's sound more like other ANJs I've heard ..."

Takatsuki TA-300B 

Kyoto isn't just great for sight seeing and eating Japanese sweets and snacks. It is also home to Takatsuki Electric Industry Co Ltd. Currently they only produce two models of vacuum tubes, the 300B and the 274B rectifier. 

Like any high-end Japanese product, the Takatsuki comes in exquisite packaging with the tubes packed securely in a wooden box, full literature on the product including individual test results from their Amplitrex tube tester. A pair of Takatsukis will set you back about USD 1,500-2000 per pair.

This was definitely a crowd favourite and elicited plenty of excited superlatives. The Takatsuki is a very clear and open tube with the widest and deepest soundstage. The top end has incredible amounts of air, which created the most realistic acoustic space among the tubes on test here. I found the staging to be slightly forward, with noticeable midrange projection, contrary to the findings of one of the participants who felt that it had recessed soundstaging.

It had less tonal density and heft compared to the Elrog, and careful matching is required to avoid excessive brightness. Otherwise, it was the clear leader in terms of detail retrieval, imaging and soundstage precision. The crowd begged for the Valvo Heerlen 12AX7 to be put in place of the Telefunken (more details below), but I politely declined to maintain a consistent test base for our shootout. 

Here are the comments from the other participants :-       

"Big soundstage, airy, good extension of highs and lows, slightly colored compared to elrog. Suitable for vocals and recitals."

"Open, lit, detailed. Excellent soundstage and so holographic sounding"

"Voicing "behind" the speakers, incredible microdetail and filled out the space. Extremely holographic, clean, and refined. the Takatsuki opened up the sound and removed the ANJ flavouring."

Sophia Electric Royal Princess

This tube was generously on loan from TC. Although he did not participate, he had very high hopes for his tube. 

This tube had two big problems, the Elrog and the Takatsuki. While the Royal Princess was more open sounding that the Genalex, this came with a subtle grit at high-frequencies. There is also more midrange glow compared to the rest of the tubes here. Objectively, this is a decent tube but viewed against the very high price it commands, it was underwhelming. According to the Sophia Electric website, these tubes cost USD 1,200 per pair. 

"Shuguang Treasure/Sophia Princess-both are good tubes. Good details. But a bit of sibilance can be heard."

"Sophia was noticeably less open, but still detailed sounding. As mentioned by Eric, the sibilant treble was a minus. Still quite holographic"

"Good soundstage, falling behind the Takatsukis, clear warmer focus and more bassy than the other two. However lack of refinement compared to both the Takatsuki and Elrog."

Shuguang 300B-Z Black Treasure

Shuguang of China makes tubes, a lot of them ! Their tubes are supplied as stock by many equipment manufacturers. In recent years, they launched their premium offering - the Treasure Series. 

Apart from differences in construction and materials, only senior technicians are deployed to assemble these. The most visually striking part of Treasure Tubes are their polymer carbon coating with gives the glass their characteristic blacked appearance.

I have previously used Black Treasure tubes, their KT88s and the CV-181. I lost one KT88 after about 500 hours, but otherwise they have held up reasonably well.

These tubes sit squarely in the middle price wise between standard and premium offerings. They typically sell for about USD 300-400 per pair. 

I found these tubes to be very good value for money. They did everything the Genalex did, with a slight but noticeable improvement. Tonally, they are warmer and denser than the Genalex, while maintaining good levels of detail retrieval. There was a bit of midrange harshness in the beginning, but this was missing by the time we reached the last test track. I suspect this tube may be a dark horse as my previous Black Treasure tubes sounded their best after more than 500 hours of burn-in.

Here are the comments from the other participants :-     

"Good tube. Good details. But a bit of sibilance can be heard."

"Shuguang was Genalex level up. Meaty and full sounding while retaining an acceptable amount of details. More refined than the Genalex."

Genalex Gold Lion PX-300B

These Russian tubes are made in the old Reflektor plan in Saratov, but under foreign ownership. New Sensor Corporation now owns the rights to a lot of the big trade names of the past and churns out an impressive line of tubes under various labels. Locally, they cost about USD 300 per pair. 

These tubes are to me perfectly listenable and very good all-round performers. You are unlikely to get any sonic wows, but there are no nasty surprises either. Tonally, they are slightly on the warm side of neutral. I thought that they had good staging and projection, but the Takatsuki showed how much was being left on the table. 

I would rate their field reliability to be similar to the Shuguang Treasure. I lost a KT-88 years ago, so that makes one death count each. Alternatively, maybe I just have bad luck with KT-88 tubes ?

Here are the comments from the other participants :-     

"Perfectly listenable if I didn't hear the rest. But after hearing the rest, it was meaty but flat sounding."  

"Good all rounder. Value-for-money."

The Unsung Heroes

We also took some time to roll the 12AX7 tube. Our host had Telefunken smooth plates installed. Changing this tube had as much effect as the 300B tubes. We tried a JJ ECC83S, and two vintage Valvo tubes, one produced in Heerlen, and another from the Hamburg plant. All three tubes had a warmer and denser tone compared to the Telefunken (no surprise really), and the host liked the Valvo Heerlen tube the best. The above shoot-out was carried out with the Telefunken tubes installed.


Your mileage will vary. Each tube will sound different when deployed in another system, due to circuit differences, as well as system synergy. 

Also to be clear, none of these tubes made the system unlistenable or objectionable in any way. As one participant pointed out, we could have had a happy outing with the Genalex if we did not hear the rest of the tubes. So please experiment for yourself and happy rolling ! 

Don't forget to let us know your favourite 300B by leaving a comment.