Audio-gd Master 10 Mk.2 Integrated Amplifier | REVIEW


When I first saw the name “Audio-gd,” I might have been a little confused. It might have been a case of an initial misread–I thought the email said Audio G-D, and perhaps the manufacturers belonged to one orthodox church or another. Ever secular, I also wondered if this was a roundabout way to squeeze some profanity into a brand name, sort of like Schiit Audio. But no, Audio-gd is the name of this brand, and hopefully the discussion is now closed.

Words and Photos by Marc Phillips

Audio-gd is another member of the Underwood Hi-Fi family. Underwood Hi-Fi, under the tutelage of Walter “Underwood Wally” Liederman and Mark Schifter, has created a unique business model in the world of high-end audio. Instead of merely acting as distributors and importers, Wally and Mark scour the globe for worthy brands that might not otherwise see the light of American day–like an importer/ distributor, I suppose. They veer from that traditional approach, however, when it comes to releasing products under their multiple marques–instead of merely bringing products to the US, they work with longtime partners all over the world to create specific products to meet Underwood Hi-Fi standards and concepts. When something turns out really good, they introduce it to the world.

Audio-gd is a slightly different case. This is a Chinese company that has been manufacturing quality high-end audio products for 20 years now. When I say quality, I mean quality. The Audio-gd Master 10 Mk. 2 integrated amplifier I received from Underwood Hi-Fi is one of those proverbial beasts, built like a tank, and beautiful to boot. It’s the type of integrated where an audio salesman would keep asking you, “How much do you think this costs? C’mon, just guess.”

If you know Underwood Hi-Fi, you’ll know the Audio-gd Master 10 Mk. 2 integrated amplifier is going to be some sort of screaming deal. I know that, because I’ve reviewed a number of Underwood Hi-Fi products over the years and each one was a screaming deal. That can be a liability in our industry, where many great products have failed because they are priced too low and are not taken seriously by well-heeled audiophiles. But once you have seat time with the Master 10, you’ll discover it’s a very serious piece of kit that also happens to sound really, really good “for the money.”

marc phillips system

Inside the Audio-gd Master 10 Mk. 2

“Remember, lift with your legs.”

Bill Leebens, who represents Underwood Hi-Fi, told me that at least a couple of times. The Audio-gd Master 10 Mk. 2 integrated weighs almost 100 pounds. It didn’t take long for the two of us to start referring to it simply as “The Beast.” The Master 10 is big ‘n’ beefy for a reason–it has 250wpc into 8 ohms, 500wpc into 4 ohms, and 1000 wpc into 2 ohms. (That weight alone should tell you this is no class D amplifier.) The build quality is impressive, with massive heat sinks on the side. Despite that formidable heft, the Master 10 is also a beautiful amplifier with a clean, practical layout on the front and back.

Is the Audio-gd Master 10 Mk. 2 a class A amplifier, or a class AB? As the company states:

“Master-10 MK2 applies ultra-low distortion single stage ACSS amplifier and soldered directly on the motherboard. The gain stages and pre-driver stages [are] working on class A. The output transistors stages working on high idle current state. The diamond cross output stage design can avoid ‘switch distortion’ as good as the class A amp.”

This implies, of course, that there’s a lot of innovation in this design, starting with ACSS. I’ve never heard of ACSS until the Audio-gd Master 10 showed up, but that’s because it’s a proprietary concept. I wasn’t able to try out ACSS for myself because the three-pin connectors on the cables are designed for use with other Audio-gd components. If I get another chance to review Audio-gd, and I hope that I do, I will ensure that I can evaluate ACSS.

I also received the following explanation from LSA on ACSS:

“ACSS (Audio-gd Current Signal System) means that the amplification occurs in the current domain, rather than voltage domain. Advantages are greater linearity, very low levels of distortion without the use of any feedback, and distortion levels that remain consistent at all frequencies—in most amps operating in the voltage domain, distortion levels vary at different frequencies. Audio-gd’s theory is that by keeping distortion consistent across all frequencies, the character of the sound remains consistent.”
In addition to two sets of RCA inputs and two sets of XLR inputs, the Audio-gd features a fifth “ACSS” input. “No matter what kind of signal it is input, it is able to transfer it to balanced current signal and amplify it,” the website explains. Here’s a little more detail:
“The ACSS is a non-feedback technology made with fully discrete amplifiers. Most people know the global feedback design can offer better specs in test measurements, and non-feedback can’t do well in test measurements but can offer better sound for the human’s ears. Here is a conflict of the classic circuits. But the ACSS opens a new field, it can offer a least coloration sound which is more neutral with very low distortion and high linearity. So it can retain the dynamics, detail and neutral sound but not sound bright or harsh.

“All signal gain is in current, achieved by the unique, superb open-loop multiple output current mirror. Incomparably precise and ultra-low distortion in the gain signal is the result. The signal path is balanced throughout and all transistors work in class A mode.

“The ACSS parts use 4 groups of high-quality class A parallel connection PSU for dedicated DC supply. The class A parallel connection PSU has very high input impedance to avoid pulse from the PSU from affecting the gain stages, and low output impedance with very fast speed and high linear, so it is a very clean power supply.”

The Audio-gd Master 10 is more than just ACSS technology with an amplifier built around it. It’s a fully balanced dual-mono design, with the channels separated by an internal shield board. The 99-step attenuator is digitally controlled and relay-based and corrects channel imbalances. PSUs abound, with four groups alone arranged as class A parallel in the gain stage. Parts quality is high, with Dale resistors, WIMA and custom Nover caps and gold-plated sockets throughout.

This looks like a five-figure integrated in almost every conceivable way. But the Audio-GD Master 10 integrated amplifier will cost you just $3,999. It’s just plain nuts when you think about it, and especially when you listen to it.



The Audio-gd Master 10 Mk. II integrated amplifier is certainly heavy, but not so much so that I couldn’t hoist it onto one of the shelves of my Fern & Roby equipment rack without injury. There but for the grace of Audio-gd. I also managed to get the Master 10 hooked up, turned on, and playing music without once consulting the owners’ manual until I needed to figure out what those ACSS inputs were doing on the back panel. I loved the generous spacing of the jacks, which aided with proper cable dressing.

I will mention one more thing–The Beast does run hot. Not KT-88 hot, not pure class A hot, but warmer than I expected. Give it some space to breathe on your rack.

The Audio-gd Master 10 Mk. 2 served as the engine of this inaugural system, the first one in my new home. I used the ArgentPur AgPur12 speaker cables between the amplifier and several bookshelf monitors I have in for review from Gershman Acoustics, Aretai, Piega and Falcon Acoustics. You might think I’d have something bigger in mind to pair with an amp with this much sheer power, but at the same time I was dealing with several pairs of “bookshelf” speakers that are ambitious when it comes to delivering the bottom octaves. The Gershman Acoustics Studio XdB monitors, for instance, claim to reach down to 23 dB, and after my initial listening sessions with the Master 10, I believe it. This was in a large room as well, with the Studio XdBs a comfortable distance from the rear and side walls.

underwood hi-fi

Audio-GD Master 10 Mk. 2 Sound

The sound of the Audio-gd Master 10 wasn’t obvious at first. During break-in, I noticed a slightly glossy surface on most of the music, something I’ve experienced–and ignored–on most class D amplifiers. But for the most part this sounded like genuine high-end audio sound full of detail, and with a distinctly low noise floor.

As time went on, the Audio-gd started sounding more like genuine class A amplification, with added textures and a greater three-dimensional feel. But this amplifier did hold onto that initial smoothness, and over time I identified this as an honest sonic signature presented by the people at Audio-gd. It’s a bit strange, though, that I thought of that smoothness in the middle treble as sounding like class D, but after a couple of hundred hours I started hearing it as that sublime compromise between solid-state and tube sound, the same compromise that led me to pure class A sound with my reference Pureaudio gear.

There is warmth with the Audio-gd Master 10. Not too much warmth, but enough to run through the meadows hand-in-hand with that smoothness. That combination led to a sense of lots of space, with superb imaging overall. Before I knew it, I considered the Master 10 as one of those Bali Hai components, a term I came up with a few years ago to describe a South Pacific feeling of warm tradewinds, exotic beaches and a wonderfully empty itinerary for the next several days.


Listening Sessions

As I mentioned, the Audio-gd Master 10 Mk. 2 integrated amplifier has been holding court in my new listening room from the day we moved into our new house. Once it settled in, I had no immediate urge to try something else. I will mention one interesting thing about the Master 10–I tried many different loudspeakers with this amplifier, and many of them sound quite different from each other. The warm, lush Gershman Acoustics Studio XdB loudspeakers, for example, sound very different from the detailed and dynamic Piega Coax 411s, and yet I truly enjoyed both of these speakers with the Master 10.

It’s similar to inviting a group of very interesting guests to a very beautiful seaside location to discuss a wide variety of topics. Each guest has their particular and cogent viewpoint, but would you look at those waves? The Audio-gd Master 10s calm and relaxed manner provided a strong foundation for every speaker to excel. If you think my upcoming loudspeaker reviews sound overwhelmingly positive, Audio-gd is to blame.

First things first–I now live in a secluded area with no neighbors close by, and I’ve been waiting for three long years to crank some tunes–even if I have nothing but stand-mount monitors. As I conducted the obligatory Yulunga and Chocolate Chip Trip tests, I noticed that despite the Audio-gd’s massive power was coupled to a feeling of precise control. It’s been a while since I’ve turned the volume knob this high, and I generally listen at consistently moderate levels, so I felt as if I’d quickly discover some type of harshness or distortion that would force me to back off the SPLs and tell myself, “That’s why I don’t crank up the volume anymore.”

But that doesn’t quite work with “Chocolate Chip Trip.” The impressive thing about this drum solo track is the incredible dynamics, which perfect the illusion of Danny Carey sitting ten feet in front of you and going to town on his kit. At high-end audio shows, I let the exhibitors crank their six-figure behemoths and blast the Aqua Velva right off my cheeks, but I heard something quite different with the Master 10 and a variety of over-achieving monitors. I felt tight-fisted control. I heard a gigantic, natural soundstage that was well-defined, with superbly focused imaging. I heard my favorite living drummer having fun in my listening room, unencumbered by technology. It was a rush.

Just because you have an amplifier with 250, 500 or even 1000 watts per channel doesn’t mean you have to play everything at rock concert levels, of course. Sure, the Audio-gd Master 10 Mk. 2 was more than willing to rattle the pictures hanging on the wall, but it supplied a generous dose of delicacy–especially when I tested out the Luxman LMC-5 phono cartridge on my Pear Audio Blue rig through the Allnic Audio H-6500. The Luxman, in one word, is delicate.

I recently purchased two more Rhymoi Music LPs, Three Wishes for a Rose (cello and piano duets) and The Dancing Girl from Izu, which gathers both Chinese and Japanese musicians to play modern songs with traditional arrangements. (We’re talking “Desperado,” “Love Me Tender” and more.) One of the reasons why I love this Chinese record label so much is their attention to timbre, especially when it comes to the more esoteric and traditional instruments. The Luxman and the Audio-gd combined to present stunning insight into these performances and the physical movement required to deliver these sounds.

Is this $4,000 solid-state integrated amplifier perfect? It might be “for the money,” but you’ll get a little more air and space with a top-notch tube amplifier such as the Allnic Audio T-2000 or even the Lab12 Integre4, which costs just a little more than the Audio-gd Master 10 and indulges my need for a little more warmth. My class A go-to, the Pureaudio amplification from New Zealand, pulls you in closer to the music while the Master 10 sometimes keeps you at arm’s length. I’m just saying that if you’re looking for an amazing $4,000 integrated amplifier with tons of power and great looks and a natural, life-like sound, the Audio-gd Master 10 Mk. 2 should not be overlooked just because you haven’t heard of them until now.


Audio-GD Master 10 Mk. 2 Conclusions

pta reviewers choiceBefore I offer my final conclusions about the Audio-GD Master 10 Mk. 2 integrated amplifier, let me remind you of some of the gear that was used in its evaluation. First, I paired it with a number of high-falutin’ loudspeakers such as the Aretai Contra 100S ($9,000/pr USD), the Gershman Acoustics Studio XdB ($12,000/pr USD), the Piega Coax 411 ($10,000/pr USD)–not your likely candidates for a integrated amplifier from China that sells for $3,999. Then there’s the swanky digital gear I brought along for the ride–the Antipodes Oladra 1 music server ($25K), the Merason DAC 1 Mk. 2 digital-to-analog converter ($8K), and the Innuos Pulsar streamer ($6,899). Even the loudspeaker cables I used between the speakers and the Audio-GD Master 10 Mk. 2–ArgentPur, Ansuz and more–cost more per run than the entire amplification.

What does that mean? I could have used my reference amplification, about $25K worth of Pureaudio from New Zealand, but I didn’t. Not once did I think the Audio-GD wasn’t up to the task of informing what each piece of the puzzle contributed to the whole.

Once again we have a product on our hands that was brought to us by Wally Liederman and Mark Schifter via Underwood Hi-Fi, and it’s more than just a great value–it’s a new way of acquiring that level of performance through a distribution model that cuts to the chase and, because it’s sold directly, gives you a more streamlined way to get what you want without surpassing your budget. If you’re one of those audiophiles who balks at great deals or value propositions in this hobby, the type who can’t take a $4,000 integrated seriously–especially when it has this much power–you should know that Underwood Hi-Fi has a strong, dedicated group of clients who respect and even love Wally for his ability to release products like this in the states. They’re rolling their eyes at the nay-sayers despite the poo-poo faces congregating along the periphery.

I do want to test out the ACSS, which opens up the possibility of more reviews of at least two Audio-gd components and the specialized cables. This company sells an extensive line of DACs, headphone amps, preamps, power amps, integrated amps and cables. They manufacture both tube and solid-state components. I think I can open my schedule up to hear more from this intriguing company.

I was so impressed with the off-the-chart value of this integrated amplifier, in fact, that I was prompted to start listing our PTA Best Value nominees for 2023. As the halfway point of the year passed by quietly a few weeks ago, I haven’t encountered anything this year that’s this amazing for the money. I might even go as far to say that the Master 10 is easily my favorite product to come out of Underwood Hi-Fi so far. That says a lot.


marc phillips system


heat sinks master 10

1 Comment

  1. Hi

    “Audio-gd’s theory is that by keeping distortion consistent across all frequencies, the character of the sound remains consistent.” qtd LSA per M Phillips.

    For only 4 grands to own a 250Wx2 integrated amp is a good deal let alone its unique current amplification topology using large bias current & zero global negative-feedback. Surely it would cost much more to buy if not made in China.

    Though solid state amps are not my cup of tea as I am a class-A tube amps addict, whoever needs large power to drive low-efficiency loudspeakers without wrecking the bank account, should go for it after favourable audition.

    JACK L

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