B.M.C. Audio CS2 integrated amplifier
- Alan Sircom
- Jan 2015
A few issues ago, we raved about the B.M.C. Audio BDCD 1.1 CD player/transport and DAC1 DAC/preamplifier. We liked these products because they represented some of the truest aspects of high-end audio as it used to mean; high performance sound, significant build quality, and ‘reassuringly expensive’ without being utterly financially unattainable. There is a big piece missing from this B.M.C. Audio line up, however: the power amp.
In this case, it’s not just a power amplifier. The CS2 is a cleverly configurable amplifier that can be used as an integrated, or the power amp in a pre-power system. Also, if used with B.M.C.’s own system architecture, it can easily adapt to become potentially an even higher level of amplifier, and the clever fibre-optic comms connections between DAC and amp (or amps) means installing the system is extremely easy.
Easy, that is, in terms of plugging the thing together. Things are a little different when it comes to physically lifting the CS2 into place. In today’s Class D, slimline world, this is a beastie. Behind the big front panel, large VU meters and huge volume and control knobs is an amplifier built for the big game. Open the amp up (not an easy task, it’s all vents and fins rather than a simple top-plate) and you are met with an exercise in transformer and capacitor use. It’s not weighed down by a heavy chassis; it’s rooted in place thanks to the sort of power reserves that could jump-start an Airbus. Any amplifier with 2kW of toroidal transformer in the power supply is very likely going to be dynamic, powerful, and stable… and the amp is all of those things.
However, it’s not simply a big amplifier. Instead, this uses B.M.C.’s own LEF (Load Effect Free) design. This uses a very small single-ended class-A output stage with a low-impedance voltage output. This stage, as well as the gain stages, has no feedback loop whatsoever. An independent circuit, not attached to the music signal, measures the current inside the voltage stage and keeps it constant by supplying an external phase independent current. Combined with a floating voltage cascade, the voltage stage hardly moves on its non-linear curve and thus doesn’t produce any THD. Uniquely, this is actually avoiding THD instead of correcting it by an overall loop.
This partners with BMC’s Current Injection system, which replaces the gain stages with a special current/voltage converter, thereby preserving the original current of the signal source through the CS2. Moreover, when used with other B.M.C. electronics, the CS2’s Discrete Intelligent Gain Management circuit moves the gain control out of the input and effectively controls level at the output stage itself, thereby reducing input attenuation and excessive noise and distortion from additional amplifier stages. It’s pretty clear this is not just another 200W amplifier.
Do not expect a plethora of inputs and outputs though. The amp has just three RCA single-ended inputs and two XLR balanced, as well as the Toslink-cabled opto control system that allows the DAC1 to take over preamplifier duties. There’s not much in the way of control, either; the big knobs turn the amp on and alter the volume, while the two buttons run through the inputs and dim that big display. The display has both power meters and a zero-to-66 volume level in 1dB steps (although using the conventional ‘more is louder’ relative scale than the correct, but counter-intuitive dB scale), and the relevant input is indicated along the top of the dial. Forget tape loops or balanceand tone controls; this is old school purist high-end, and arguably all the better for it.
Like the CD player and DAC before it, there’s actually not much you need say about the sonic performance of the CS2. And what you do say, tends to be reflections of negative aspects of other products in its price class. In other words, “X isn’t as detailed as the CS2” or “Y isn’t as dynamic as the CS2”. But, even pulling out these aspects is doing the B.M.C. Audio something of a disservice, because it implies individuated aspects of a performance, where the CS2 shines in delivering the whole package.
You don’t focus on the ephemera here. You aren’t listening for the detail or defining the soundstage. You are listening to music, as a complete and contiguous whole. It’s like it manages to combine the grace of a good valve amp with the power of good solid state. That combination of effortless power and a lot of respect for the music makes the CS2 the perfect foil for some of the larger, more demanding, and great sounding loudspeakers out there. They brought my Wilson Duette Series 2 to life (but that’s not really difficult), they brought Avalon Transcendents to life (a much harder proposition, especially in a small room), and practically everything you could put on the end of this amplifier sounded like it should.
The CS2 presents the sound it’s fed honestly and accurately. It’s fundamentally neutral to the core, and that is what makes it so attractive for use with high-end loudspeakers. I’m finding it a little difficult to be entirely rational about this because of what it represents (high-end the way it always used to be) as much as how it sounds, but the fact is it sounds extremely good indeed.
We’ve lost our way a little, and the musical examples audio reviewers pull out of the hat can sometimes reflect this. It’s a function of preaching to the choir and not having enough new blood to be able to play a more diverse range of albums. But the CS2 needs none of that selective audiophile album nonsense. It’s just as comfortable wigging out to Puscifer as it is being cerebral to a Mozart piano concerto. While that doesn’t make for pulling out good musical examples to highlight performance aspects (just point the amp at your collection and you’ll find such examples) it does make for an amplifier that at once ticks the audiophile and the everyman boxes alike.
We had this amp (and its monophonic M2 counterpart) at last year’s Whittlebury Hall show, playing in a huge room with a pair of large Usher loudspeakers and a lot of GIK Acoustics room treatment. In truth, I didn’t expect it to work as well as it did given the size and volume constraints of the room, but the level of grip and control this amplifier brought to the party helped a lot. Any loss of control in this setting would set the room off in an instant (a pair of LS3/5as could boom in that room) and the loudspeakers were more than capable of putting a lot of energy in that room, and yet it worked. OK, so playing ‘Chameleon’ from Trentemøller’s The Last Resort [Poker Flat] triggered the aircon ducts to start rattling, but that would happen regardless. Fact is, this amp made the sound ‘right’; tonally neutral, as dynamic as the source, detailed, and fast in one fairly heavy package. We briefly moved over to the M2s and game was raised, although this proved almost overkill, because the amount of control meant you could push the system to the limits, which meant Wagner, played at whirlwind-raising levels. At one point I turned the volume, looked over my shoulder and saw people cowering – not wincing, but physically cowering from the power this system was capable of producing.
A brief word on cables. B.M.C. has its own monocrystal cable at a less heady price point than the usual suspects that works extremely well, and Colab distributes the excellent Iso-Kinetik Cabezon cables that also make a great case for their inclusion in any system. Were it not that the CS2 does its job so well that you end up thinking everything else a footnote, these would be stars of the show. I suspect in an ‘all roads lead to Rome’ manner, there will be many who start speaking to Colab through the medium of Cabezon cable and end up catching the B.M.C. bug. But, whatever, it’s all good.
I’m surprised by the CS2 and by the state of the rivals at the price. There are a lot of amps at this price point, but few seem to hold that goal of ‘high fidelity’ in as such high esteem. Some place emphasis on aspects of musical performance or on shaping the tonal balance in manners euphonic, quixotic, exotic, or neurotic. And some will be drawn to one of these outcomes. But is it right? The B.M.C. Audio CS2 asks this question of its rivals, and many will shy away from the answer.
I think B.M.C. is the intelligent choice in high-end audio right now. Aside from the monoblock option, you have to spend more – vastly more, an order of magnitude more in fact – to achieve any significant uptick in performance. There are many who say there’s no such thing as a law of diminishing returns in high-end audio, but I’d disagree. For me, it starts where B.M.C. Audio stops. Highly recommended.
- Type: Integrated amplifier:
- Inputs: 2x balanced XLR and 2x unbalanced RCA
- Input Impedance: 50kΩ to ground, 100kΩ differential at XLR
- Input Sensitivity: max 750mV (RCA), 1.5V (XLR)
- Output: 2x 200W/8Ω, 2x 360W/4Ω
- Frequency response: 20Hz-20kHz +0dB/-0.08dB @ 1W
- THD+N under 0.1%: from 0.3mW to 150W
- Signal/Noise ratio at DIGM 40 (relative to 1W): 103dB
- Damping factor: 250
- Dimensions (WxHxD): 43.5x45x15cm
- Weight: 40kg
- Price: £4,595 (M2 mono amp, £4,595 per channel)
Manufacturer: B.M.C. Audio GmbH
UK Distributor: Colab Audio Ltd
Tel: +44(0)7768 720456
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