B.M.C. Audio CS3 integrated amplifier

A couple of years ago, we raved about the B.M.C. Audio CS2 integrated amplifier, for a number of good reasons. Like the CD player/transport, DAC, and power amps – and supposedly like the phono stage – we liked the B.M.C ethos and its products because it all represents some of the truest aspects of high-end audio as it used to mean; high performance, significant build quality, and something ‘reassuringly expensive’ without being utterly financially unattainable. But this year, the CS2 received some useful upgrades and became the CS3. How could we resist the chance of a revisit?

Like its predecessor, the CS3 is a cleverly configurable amplifier that can be used as an integrated amplifier, or the power amp in a pre-power system. Part of the reason it can so readily be swapped from one to the other is that it’s in essence a power amplifier with what B.M.C. calls its Discrete Intelligent Gain Management system and a source selector. Usually, integrated amplifiers are a cross between a preamp and a power amplifier in one chassis. Used with a suitably equipped DAC, the whole gain structure of the amplifier is modified on the fly to suit the volume level set by the converter. This is different from signal attenuation, it’s more like changing the size of the amplifier relative to the volume level.

Discrete Intelligent Gain Management circuit moves the gain control out of the input and effectively controls the level of the output stage (thereby reducing input attenuation and excessive noise and distortion from additional amplifier stages). Of course, a ‘suitably equipped DAC’ is one of B.M.C.s own and this therefore relies fully on B.M.C.’s own system architecture. Without that we are just looking at a very heavy integrated amplifier, albeit one that retains that DIGM circuit as part of its internal make-up. From memory, the effect was more marked when used in harness with a whole B.M.C. system, but equally from memory CS3 seems to be a bit more volume-precise than CS2.

In outright, absolute terms, there’s not a great deal of difference between the CS3 and CS2 it replaces. They deliver identical specifications, have indentical inputs and outputs, and even the dimensions of the amplifiers are basically the same. The change is down to a revised circuit designed to increase stability and make the sound of the CS3 even less compressed and more dynamic than before. In theory there is an upgrade path between CS2 and CS3, but unless you were using them in mono amp mode, with a CS2 on one channel and a CS3 on the other, I would struggle to think why you should make the jump. Especially as that would mean loading that 40kg amplifier back into its box.

In today’s Class D, slimline world, this is a beast. Behind the big front panel, large white blue 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. This has not changed. It’s not simply a heavy chassis; it’s rooted in place thanks to massive power reserves. Any amplifier with 2kW of toroidal transformer in the power supply is very likely going to be strong and stable… and not in the ‘Theresa May’s mantra’ sense!

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.

Partner this to its Current Injection system (which replaces the gain stages by a special I/V converter that maintains a low impedance through to the loudspeaker output voltage, thereby preserving the original current of the signal source through the CS3) and – especially when used with other B.M.C. electronics – it’s pretty clear this is not just another 200W amplifier.

Like its predecessor, the amp has just three RCA single-ended inputs and two XLR balanced, as well as the Toslink-cabled opto control system, which allows B.M.C.s own DAC1 to take over preamplifier duties if called upon. 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 white blue display. The display has both power meters and a zero-66 volume level in 1dB steps (although using the conventional ‘more is louder’ relative scale than the counter intuitive dB scale), and the relevant input is indicated along the top of the dial. Forget balance, tape loops or tone controls – this is old school purist high-end, and arguably all the better for it.

Given the weight, the huge warning on the box telling users not to rest the amplifier on its knobs, or store it fascia down, is probably wise. As is finding at least a couple of strong people to lift it out of the box.

Like the CS2, the CD player, and DAC before it, there’s actually not much you need say about the sonic performance of the CS3. And what you do say, is often just a reflection of the weaker aspects of other products in its price class. In other words, “X isn’t as detailed as the CS3” or especially  “Y isn’t as dynamic as the CS3”. 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 CS3 –like its predecessor 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 CS3 the perfect foil for some of the larger, more demanding, and great sounding loudspeakers out there. And yet, used with more humble loudspeakers and you get a smaller, more taut sound. The CS3 is the combination of mail’d fist in velvet glove with a gentle soul at its base. It’s tempting to use this amplifier with difficult loudspeaker loads at high volumes, because the amp can take it and it’s fun, but this is also an amplifier for the long haul. It sounds good, honest, and accurate whatever you throw at it, or whatever you throw it at.

Having some water under the bridge between the CS2 and CS3 does make for some observations, that either I missed last time, or maybe have become more important to me over the last few years. The sound of the B.M.C. is very much in the big amp design, but in some respects its very much in the older big amp, er, camp. This is a surprisingly fast sounding amplifier all things considered, but it’s not the most rhythmically precise as I’ve heard of late. I do think I am becoming more aware of rhythmic properties of music recently, or more particularly, I’ve become less tolerant of their absence. I’ve still not quite reached that level of tunesmithery that means you can walk into a room, listen to someone count off a four-four beat, and then walk straight out saying “it doesn’t time”, but that temporal and rhythmic precision I once had from smaller Naim amps is calling again, and it’s somewhat found wanting here. This is an incredibly powerful amplifier that puts a smile on your face, makes music sound exciting and percussive when called for, but there’s just that niggling little need to tap your foot along with the beat, which this gets so close to fully achieving. For many, this is a non-issue, and the combination of dynamic range, excellent soundstaging, and almost perfect vocal articulation will outweigh any perceived pace issues. But I stuck on ‘Come Together’ from Abbey Road by The Beatles [Parlophone, CD] and Ringo Starr’s louche drum style was almost too correct.

Regardless, the CS3 presents the sound it’s fed honestly and accurately. It’s fundamentally neutral to the core, and that is what makes it so attractive to 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 CS3 needs none of that selective audiophile album nonsense. It’s just as comfortable playing Puscifer as it is being cerebral to a Mozart piano concerto. And 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.

A brief word on cables. Don’t get too fussed by them. B.M.C. still makes its own monocrystal cable at a less heady price point than the usual suspects and that works extremely well. But, frankly, the CS3 is not a fussy amplifier in terms of cable demands. I found it worked extremely well with Cardas Clear interconnects and speaker cables, and I didn’t feel the need to push the envelope to something in the hyper-price league. The CS3 is best used in balanced operation if it is not to be in an all B.M.C. rig. Single-ended is pretty good, but not quite as essential as balanced and you would be strongly recommended to go for this connection if it were at all possible. But, more importantly, remember the ‘it’s not fussy’ line.

Having lived with the CS3, I am reminded of the CS2, and the question deserves repeating – Is it worth upgrading or changing from one to the other? The answer is a resounding ‘no’. Not because the CS3 is worse than the CS2. It’s ever so slightly better, in fact. And that’s why I suggest holding off. If you have a CS2, you already have a great amp with years of life in it. If you haven’t, check out the CS3, because it does practically everything a classic Krell does, for less.

I was surprised by the CS2 and what it did so well is aped by the CS3, and it still highlights 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 CS3 asks this question of its rivals, and many will shy from the answer.

What held for the CS2, and still holds for the CD and DAC, holds just as much with the B.M.C. Audio CS3. This is the intelligent choice in high‑end audio right now. Aside from the CI monoblock option, you have to spend more – vastly more, an order of magnitude more in fact – to achieve any significant uptick in performance in every aspect apart from possibly its portrayal of musical timing, and even that’s questionable. 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.

TECHNICAL SPECIFICATIONS

Type: Integrated amplifier:

Inputs: 2× balanced XLR and 2× unbalanced RCA

Input Impedance: 50kΩ to ground, 100kΩ differential at XLR

Input Sensitivity: max 750mV (RCA), 1.5V (XLR)

Output: 2× 200W/8Ω, 2× 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 (W×H×D): 43.5 × 45 × 15cm

Weight: 40kg

Price: €5,998

Manufacturer: B.M.C. Audio GmbH

URL: www.bmc-audio.com

Tel: +49 30 692 006 061