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2014 Midwest Audiofest Tent Sale & Vintage Audio Swap
Audio Music 805S Monoblocks / RT-2 Preamplifier Review
I used to think that the law of returns was cast-iron; up to a point you get what you pay for, beyond it, progressively less for considerably more outlay. Yet recently I’ve heard two absolutely rocking systems built around some really quite humble components. A lot, for a lot less, is entirely do-able.
Go to a live acoustic music event and it’s the headroom that is most noticeable. Even an instrument as delicate as a solo violin is felt close up as visceral, physical. And so what I listen for in any audio system is first and foremost dynamics. I’d go as far as to say that for me, 85% of musical satisfaction is not in the timbre, or the soundstage, or in a finger-on-chin appreciation of a ruler-flat frequency response. Without dynamics two-channel is mere musical wallpaper – an uninvolving event pasted to the front wall of the room.
Don’t kid yourself Wayne. It’s not about Watts. You’re unlikely to achieve my kind of satisfaction from speakers that are inefficient, no matter how much solid state grunt you throw at them. And particularly with tube amplification, interconnects too make a profound difference, with low capacitance, low inductance designs more often than not enabling well-founded components to produce notably more openness and dynamics than does any old connectivity string.
What prompted this mini-essay on the world according to KevinF was the loan for review purposes of a rather interesting combination of a pair of monoblocks and a tube pre-amplifier designed and manufactured in China by Am Fang, a Chinese gentleman who now heads his own Audio Music brand having previously been for some years the design brains behind Silver Knight. The AM805S monoblocks and RT-2 preamplifier are imported and retailed by Iain Borthwick of LW Audio in Bury St. Edmunds. We are, aren’t we, long past the point where mention of Chi-fi prompts a snigger from the back of the class? Really, if you think that nothing worthy of being called hi-end comes out of China, then perhaps you need to get out more.
Still, the Audio Music combination is a bit of a paradox: on the one hand at circa £16k it is emphatically in the realm of unobtanium for many people, yet it is not so stratospherically costly that it’s only affordable by investment bankers and members of the Islington or Edinburgh elites. If its price point is neither one nor the other, then the technology similarly faces in two directions at the same time, being part tube and part solid state.
The AM 805S monoblocks (£8,500) use 805 broadcast triodes as their output device, yet employ integral solid state, not tube rectified power supplies. The RT-2 preamplifier (£7500) is also hybrid in the same way – solid state power supply followed by tubes – in this instance 6H30 as drivers and a pair of 6922s to provide voltage gain. Mr Fang does not approve of tube rectified power supplies. When I enquired why via email he replied that they are invariably noisy, introduce distortion and don’t enable a firm grip over bass frequencies to be achieved.
That assertion will come as a surprise to the many manufacturers who do use tube power supplies in their products with great success, including Modwright, whose truly excellent LS 36.5 preamplifier was the subject of my last review for the ‘wam. The LS 36.5 preamp has a tubed power supply and yet not only has a vanishingly low latent noise level, but exerts astonishing grip, most evidently at the bottom end of the audio spectrum.
Superficially the 805 tube looks on paper to be the answer to many a maiden’s prayer. It is the most powerful of the 211 family, in the AM 805S able to achieve an output of 45 Watts even in single-ended mode.
But the 805 has a high impedance and was designed for class C applications where it would drive a constant load, no-one worried about distortion and where a low impedance driver stage was easily to hand. A designer I discussed it with told me that it could be used with great success for high power sound reinforcement – 500 Watts and up – but in class A single ended mode its design characteristics pose real challenges that can only be overcome by applying loop feedback in order to achieve a respectable damping factor (and this is either desirable or not, depending upon your personal view), and by making a driver stage able to provide zero power at points in the audio band when the tube’s grid is negative, yet at other points when the grid is positive, deliver low impedance grunt, otherwise output is not linear across the audio band.
Remarkably, Mr Fang has pulled it off, creating in the AM 805S (the ‘S’ signifies silver, by the way) a monoblock whose sonic traits will appeal strongly to a wide section of the buying public. A pair of them sound quite powerful and controlled, yet have a good touch of the mid-range magic that many people love triodes for. I fancy a large part of that achievement is less to do with the 805 tube and a lot more to do with the truly excellent quality of the transformers that Audio Music designs and makes. Opinion differs but for every audio designer that claims OTL is the way to go, there are many more that say only transformers can deliver. As a consumer, not a designer, I am in the latter camp. Why would anyone go OTL? Because it’s cheaper and demands way less of your designers and manufacturing process, that’s why. Does it sound as good as a well executed tranny amp ? Hell no, in my view. Am Fang understands this and has done the hard yards to develop some seriously good transformer iron and windings.
The build quality of the AM 805Ss and the RT-2 is right up there among the best. Does Mr Fang have a relative who owns an aluminum plant? Looking at the amplifiers you have to wonder; the monoblocks and the preamp use aluminum so thick, so massively internally braced in the corners and so beautifully machined that they give the impression cast monolithic integrity rather than of something that’s been screwed together. With the lids of the RT-2 and its companion power supply removed, and the base plates of the monoblocks set aside it’s evident that the quality is more than simply skin deep. In addition to the own-build transformers Audio Music has copper foil capacitors of its own design manufactured in its own factory in Mexico. Am Fang and his colleagues liked what Jensen, Audio Note and a few others were producing, but didn’t like the prices, so decided to set up in competition. Audio Music U-Caps are the result.
Internally, the RT-2 especially is a work of art. It is properly dual mono from power chord onwards. The feed splits as it enters the power supply chassis to feed two separate circuits, then travels to the preamp via separate ubilicals. To the front of the preamp box, massive machined alloy yokes hug the two 33-step-transformers for volume control, and at the rear another yoke holds the two larger output transformers. Across the middle is a vertically mounted tube socket board bolted onto its own, again massive, aluminum plate. Signal path capacitors are AM’s own U-Caps. The point to point wiring, all silver, is neatly executed. In all, it’s a joy to behold, especially when lit by the four tubes, which is why Iain Borthwick provides owners with an optional Perspex top plate so that the beauty can be more easily admired. You don’t want to be moving the AMs very often though. Each 805S weighs 31 Kg and the RT-2 and its companion power supply together a back-popping 38 Kg. Their combined weight did not push my 40mm oak audio table beyond its design envelope, but I fancy some of Iain’s customers for the 805S monoblocks and RT-2 are going to have to factor in the cost of more robust racking.
The RT-2 accepts just three single-ended or XLR balanced inputs. The front panel is simplicity itself with left and right channel volume controls either side of a rotary three position input selector switch. Tiny green LEDs indicate the position of the volume control settings.
The AM805Ss are similarly massively engineered in machined aluminum. The double C-core output transformers, mains transformers and driver transformers are hidden beneath aluminum shrouds. On the top surface sockets accept the 6V6 drivers, ECC88 amplifier and 805 output tubes. At the rear, behind the transformer shroud, are vertically mounted speaker binding posts, biasing test meter points, mains socket, plus balanced and RCA inputs.
Mr Fang describes himself as a self-confessed extreme audiophile for whom the best possible reproduction of symphonic music in all its complexity is the audio goal. In our exchange of emails via L W Audio, he identified three critical areas that AM pays great attention to in all its designs.
“The soul of a tube amplifier is its transformers, so I have spent more than ten years on
research and development, not only designing transformers for our products, but also
developing a high-accuracy machine which can wind two transformers at the same time. This helps us achieve consistency and symmetry between left and right channels.
“As you know, capacitors too are very important and influential to the sound. We use a large number of capacitors so we did the research and now make our own capacitors in our own factory. As well as wiring, we pay great attention to how acoustic vibration affects the sound of an amplifier. This tells you why we build the way we do, using such thick materials, very accurately assembled. Apart from good basic circuit design, all of these factors play a part in how a product will sound.”
For the review I teamed the AM amplifiers with Audio Note AN-E Spe Signature speakers and my own Origin Live vinyl rig and Audio Note CD transport and DAC. Interconnects and mains cables were a mixture of Audio Note litz and Cut Loose silver ribbon .
I initially introduced the 805 monoblocks on their own to the system, using my Audio Note M8 phono preamp to drive them. My immediate reaction, once I’d got over the heat produced by the 805 tubes, and the strong white light they emit, was one of surprise. Ultra quiet with no tube rush or hum to intrude into the music, the 805Ss have a dry muscularity. In the midband they lent voices some of the luminosity that SETs are famed for, and they gave a good sense of air, but at the bottom end they tended to sound arid, with less of the textural bloom that people tend to associate with tubes, and which many audiophiles criticise.
The substitution of the RT-2 for my own Audio Note M8 in the system showed what a class act the Audio Music preamplifier is. It is astonishingly quiet, pleasingly to my ears on the warm side of neutral and, as one might reasonably expect given their common design and manufacture pedigree, proved a good match with the 805Ss. I was lucky enough to have a Leema Elements Ultra phono stage here on loan at the same time, so was able to press this into service with the RT-2 to play vinyl as well as CD material. As was noted by the ‘wam’s James Palmer, the Elements might be characterised as belonging to the more ‘assertive’ end of the phono stage spectrum, and careful system matching can pay dividends. However, it worked well with the Audio Music combo, delivering detail without sounding granular and hi-fi. I suspect the Audio Music amplifiers relative laid-backness had quite a bit to do with this.
Did I mention that before? Aaah yes. The AMs are indeed laid-back. I don’t intend that to sound in any way pejorative or critical. I get what Mr Fang has set out to achieve with his voicing of the amplifiers and I think to a very large extent he’s succeeded. Feed them with his beloved symphonic music and they respond with a presentation that many people will find impressive and very satisfying. They present complex layers with an unforced clarity, throwing among the most remarkably detailed sound stages I’ve ever heard in my listening room. They also have a top-to-bottom evenness about them that doesn’t highlight any particular frequencies at the expense of others. This may well be in large part due to the lack of capacitors in the signal path. However, I found that with simpler combo jazz and other forms of acoustic music the 805Ss were less convincing for my tastes. While they do as previously noted have a large helping of that triode-sound in the midrange and, therefore render voices very well, and also deliver the leading edge of notes in a way that that illuminates nuances of timing, still there was something about the presentation that I couldn’t immediately put my finger on.
Switching back and forth between other kit including my Yamaha CR1000 receiver configured for power-amp-only mode, I eventually cottoned on; the sonic character of the AM805Ss is a halfway house between tube and solid state. While they don’t have quite the easy loose-limbed muscularity that some similarly priced tube amplification can deliver, they do sound powerful and driving in a solid-state kind of way. Mr Fang has created in the AM 805Ss a duo of amps that are at home in a niche of the market that is not over-served at the moment – people who perhaps like the look of tubes and for whom that tubey midrange is appealing, but who can’t live with the distortion of tubes, and can’t live without what they think of as a more truthful solid-state-style bass. As such the 805Ss are an astutely pitched product aimed at the majority buyer rather than the tube purist like me.
From that very personal perspective though, I think the RT-2 is a veritable blinder, able to mix it with some very illustrious and expensive company indeed. I tell you, it pushed my own Audio Note M8 hard into a corner. Nose to nose it asked: “You really worth that much, big boy?” Of course, and ultimately given the law of diminishing returns, the question is not so much one of £££s worth, but of sonic satisfaction. In others words eight point five tenths versus ten tenths – but for a lot, lot less money, if you want to characterise it that way.
The RT-2 is genuinely that good sonically, in my view. Its minimalist approach to input flexibility and user convenience probably doesn’t make it a particularly easy sell. Without a remote control it forces users to get up from the listening chair to change volume, and it only switches three sources. But does that honestly matter much when sonic quality of this order is available? Better yet, if £7,500 is too much to spring, there’s always the RT-1, copper wired version instead of silver, but otherwise identical in design and component quality for £2000 less. I haven’t heard one myself, but I bet it runs the RT-2 very close indeed.
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