Thursday, May 1, 2008

Flying Mole CA-S10 integrated amplifier

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The naming of audio companies is a tricky business. Ideally, the name should be distinctive, so that people will remember it, and descriptive of the products. However, given the proliferation of audio manufacturers, it's getting more and more difficult to come up with a name that fulfills these criteria, and some names are similar enough to lead to confusion. In one of my show-report blog entries from the 2007 Consumer Electronics Show, instead of correctly listing a company name as Divergent Technologies, I called it Definitive Technologies, which is the name of an another audio company—and was rightly chastised for it in a comment by a reader. I'll bet that no such confusion will occur in the case of Flying Mole Electronics. (As far as I know, there is no Flying Groundhog Electronics.)

My first encounter with Flying Mole products was at Home Entertainment 2006, and I was impressed with their demo. Although I hadn't heard of Flying Mole before that, I found out later that it is not the tiny company that I somehow assumed that it was. Flying Mole amplifiers apparently have a considerable following in Japan, where, according to their website, the company's monoblocks were the fifth-best-selling amplifiers in 2005. The name of the company, which was founded in 2000 by some ex-Yamaha engineers, is said to represent "accomplishing the impossible by tireless efforts underground." Flying Mole Electronics' motto is "Resolution Revolution," and their products are said to be "in harmony with nature and are environmentally friendly." The CA-S10 ($2000) is the latest Flying Mole product to embody this philosophy.

Description and design
Flying Mole takes pride in making their amplifiers small. At roughly 11" wide, 2" high, 10" deep, and weighing less than 9 lbs, the CA-S10 is smaller and lighter than most preamplifiers, let alone an integrated amplifier with 100Wpc output. However, the expected relationship between size/weight and output capability assumes conventional analog amplification. The CA-S10 is one of the new breed of digital amplifiers: it has a switching power supply.

The design of the CA-S10 (described in some detail here) appears to be quite sophisticated, with careful attention paid to every aspect of the circuitry. The first thing to note is that the amp is not based on the ubiquitous ICE module from Bang & Olufsen (used by, among others, PS Audio and Jeff Rowland Design Group), but uses Flying Mole's own proprietary By-Phase PWM circuitry. The CA-S10 features dual-monophonic construction, with a high-power switching power supply. Both digital and analog negative feedback are used to eliminate sonic problems caused by AC voltage fluctuation. The CA-S10's overall efficiency is 85%, in line with Flying Mole's environmental concerns.

Flying Mole takes a minimalist approach to inputs, controls, and outputs. There are just three sets of RCA inputs, a pair of speaker connectors, and a source-selection knob, power button, and volume control (no balance). The speaker connectors take only banana plugs or bare wire (if it's not too thick), not spades of any sort. My favored Nordost Nirvana speaker cables use spade lugs; Nordost kindly sent me another pair of Nirvanas, equipped with bananas at the amplifier end.

Although the CA-S10's appearance and price are not those of a luxury product, its fit'n'finish are excellent, the brushed aluminum case suggesting a component costing well more than $2000. Still, near the end of my time with the CA-S10, when I pulled the interconnect from one of the input jacks, the ground part of the jack came out with it, and I could see no easy way of putting it back in. For the rest of my listening, I used one of the CA-S10's other inputs.

My Avantgarde Uno 3.0 speakers have a sensitivity of over 100dB and do not take kindly to noise anywhere in the system. When I introduced the CA-S10 into my system, the level of noise—mostly a kind of buzz, with hum components—was excessive. I've encountered this sort of problem before; the solution usually involves changing the grounding of components in the system. So I did that, alternately connecting and floating the grounds of the CA-S10 and the digital source components. Nothing seemed to make much of a difference. I even temporarily unplugged the Unos' powered subwoofers, to see if there was a ground loop involving the subs' amplifiers, but no luck there either.

In the past, I've found that preamps and power amps with noise problems usually sound better when plugged into one of the regenerated-AC outlets of the PS Audio P500 Power Plant power-line conditioner. No matter how good a preamp or power amp's built-in power-supply filtering, supplying it with the pure AC of the Power Plant can have only a positive effect—or so I thought. When I was trying the various grounding arrangements, the CA-S10 was already plugged into one of the P500's regenerated-AC outlets. Finally, I tried plugging the CA-S10 directly into an AC outlet in the wall—and, to my surprise, the noise was considerably lower in level (footnote 1). It was still audible from the listening seat when nothing was playing, but now the level was low enough to be masked by music played even at a low level.

Because I couldn't use the P500's normally superior regenerated-AC mode with the CA-S10, I thought perhaps I could try one of its Ultimate Outlets, which uses passive filtering. That turned out to be the best solution in this situation, the noise being slightly lower than when the CA-S10 was plugged directly into the wall outlet, and much lower than through a regenerated-AC outlet. I used that hookup for the rest of my listening.

Listening I: Break-in
Initial impressions of the Flying Mole CA-S10: great clarity, lots of detail, excellent bass, but an excessively bright tonal balance. Chesky's familiar Jazz Sampler & Audiophile Test Compact Disc, Vol.1 (Chesky JD37) sounded as if it had been remastered, with re-equalization that made the percussion instruments on track 3 have more presence than I'd heard before, but with an unnaturally edgy timbre that suggested synthesized versions of the real things. The DePaul University Jazz Ensemble's Big Band Basie (Reference RR63-CD), which I don't think was recorded with a particularly forward or treble-emphasized tonal balance, sounded similarly edgy, the trumpets having a piercing quality that went beyond what these instruments actually sound like in real life. Recordings that themselves have a bright, forward tonal balance, such as Christiane Noll's Broadway Love Story (Varèse Sarabande VSD 5956), one of my 1999 "Records To Die For," were virtually unlistenable at anything other than a background level. This was after all the changes in grounding described above; the Flying Mole was hardly "just out of the box."

So, was this what the CA-S10 "really" sounded like? Before accepting that conclusion, I had some alternative interpretations to consider. One possibility was that this was one of those components that take a long time to break in. The break-in phenomenon, though scoffed at by much of the traditional audio-engineering establishment, is well known to audiophiles, and I've had experience with components whose sonic characteristics changed significantly during the evaluation period. Some components sound much the same after several months' use as they do when first turned on; the changes, if they occur, generally involve a "relaxing" of the sound, the highs becoming less prominent, less forward. A second possibility was that the CA-S10 was interacting in a negative way with one or more of the components in my system. My experience with the CA-S10 "not liking" the balanced AC from the PS Audio P500 made me alert to this possibility.

I spent a greater-than-usual amount of time investigating these possibilities. First, I left the CA-S10 on all the time. This is not generally considered to be enough for break-in, but it can help. Then, whenever I left the house and there was no one else at home, I left the system playing at a fairly high level. I even dug out Purist Audio's The System Enhancer, a CD containing complex tones that are supposed to be particularly effective in facilitating the break-in process, and played it, on and off, for a total of about 24 hours. At other times during the evaluation period I tried substituting various components in the system: interconnects, speaker cables, digital front-end.

Judging potential changes in the sound of a system over a period of three months is a difficult process. In addition to changes in the sound itself, there is the possibility of the listener "getting used to" the sound—or, conversely, becoming aware of aspects of the sound that were previously not noticeable. Still, I'm reasonably confident in reporting that the sound of the CA-S10 did change during the evaluation period, and in the direction that I had hoped for.

Footnote 1: I told PS Audio's Paul McGowan about my experience, and the first question he asked was whether the amp I was using (which I did not identify) had a switching power supply. I told him it did, and he said that some amplifiers with such supplies "don't like" the balanced AC supplied by the P500. (Interestingly enough, PS Audio's own GCC-100 integrated amp has a switching power supply, and works just fine with power from a filtered or a regenerated-AC outlet.)

There were also some changes as a function of its interactions with associated equipment. The only change of this sort that was unequivocally beneficial was my replacement of a 5m run of Nordost Quattro Fil interconnect between the digital front-end and the CA-S10 with the same length of PS Audio xStream Statement. The Quattro Fil is my preferred interconnect between my Convergent Audio Technology SL-1 Ultimate preamp and Audiopax Model 88 power amps, but with the digital source driving the CA-S10, the xStream Statement gave the sound a more forgiving character, detail still there but not thrust at me to the same extent. I don't know why the PS Audio xStream Statement interconnect worked better with the CA-S10 than the Nordost Quattro Fil, but if I had to guess, it would be to suggest that the Flying Mole might be particularly susceptible to EMI/RFI, that the long interconnect acts as an antenna, and that the xStream Statement's triple insulation is better at rejecting this sort of interference.

Substituting other components—an Onkyo DX-7555 CD player for the complex digital source of PS Audio transport and Perpetual Technologies/Modwright digital source, and various other cables I had on hand for the Nordost Valhalla speaker cable—also changed the sound, but not in ways that I could unequivocally say were improvements. The use of Aurios component supports, which provide a benefit with most electronics, made no difference that I could hear.

Listening II
Eventually, the CA-S10 apparently reached some sort of break-in plateau (it's hard to be absolutely sure about this sort of thing), and the PS Audio xStream Statement interconnect brought its virtues more to the fore. "Resolution Revolution" is not merely a marketing slogan. The CA-S10's resolution of details of vocal and instrumental performances and spatial definition—as well as technical details of recording such as an editing glitch I've mentioned before, on Sylvia McNair's Sure Thing: The Jerome Kern Songbook (CD, Philips 442 129-2, track 10, 1:35)—were about as clear and detailed as I've heard with just about any combination of preamp and amp. The sound had a lively, dynamic quality that made it easy to follow rhythmic patterns such as those on Mickey Hart's Planet Drum (CD, Rykodisc 10206).

Having said that, musical is not the first word that would occur to me to describe the sound of the CA-S10. Perhaps accurate. I found much to admire in the sound, but even after the long break-in and efforts to provide a more synergistic match with associated components, it was still a bit too much on the clinical side for my taste. To use an analogy with digital photo processing, the sound of the CA-S10 was like a photo whose apparent ultrasharpness has been produced by somewhat heavy-handed application of Photoshop's Unsharp Mask sharpening tool. At first glance, the image looks very sharp, but a closer examination reveals that the edges have been emphasized, and that there are faint halos around the outlines of objects. I wouldn't take this analogy too far, but if the CA-S10 had a Sharpness control, I would have wanted to turn it down a notch or two. Judgments of sharpness of photos is very much a subjective thing, and people differ in their preferences. I would expect that people will also differ in their responses to the "sharpness" of the CA-S10's presentation.

Compared to...
The Flying Mole CA-S10 was the second digital amplifier I've had a chance to evaluate at some length; the first was the PS Audio GCC-100 (Stereophile, January 2006, Vol.29 No.1). As I still had the review sample of the PSA on hand while reviewing the CA-S10, a comparison seemed in order.

I found the products similar in a number of ways: they're both integrated amps (although PSA calls the GCC-100 a "variable gain power amplifier"), both are rated at 100Wpc, and both use class-D amplification. However, the GCC-100 is a fully balanced design, with a more extensive array of inputs, a left/right balance control, a remote control, and a numerical readout. It's also much bigger and heavier than the CA-S10 (26 lbs vs 9 lbs) and costs more ($2795 vs $2000).

In my review of the GCC-100, I said that the interconnect that sounded best with it was the Nordost Quattro Fil—better than PSA's own Audio xStream Statement. And as I've said above, the opposite was true for the CA-S10. I hate this sort of interaction! To keep potentially confounding factors constant, I used both the CA-S10 and the GCC-100 with the xStream Statement, which favored the CA-S10. For comparison purposes, however, I decided to use each amplifier with the AC source optimal for it: PS Audio Ultimate Outlet passive-filtered for the CA-S10, and one of the P500's regenerated-AC outlets for the GCC-100. Levels, measured with a voltmeter at the amplifiers' speaker terminals, were matched to within less than 0.2dB. I think precise level matching is critical only for rapid-switchover comparisons, but, hey, it can't hurt.

The most immediately obvious difference between the two amps was in their levels of noise: with the CA-S10, as noted above, some audible buzz/hum came through the speakers; the GCC-100, while not having absolutely the lowest noise I've had in my system, was considerable quieter. The noise in both cases was audible from my listening seat only when there was no music playing; at even a fairly low level, music masked the noise in both cases.

The amplifier sections of the CA-S10 and the GCC-100 operate in class-D and so might be expected to sound alike. There were some similarities, but they were largely eclipsed by the differences. Both can be described as high-resolution amplifiers that do not gloss over or smear sonic subtleties present in the source. The amps' top and bottom extensions were comparable, the CA-S10 sounding a bit cleaner in the midbass. However, the GCC-100 managed to avoid the clinical, ultrasharp presentation that characterized the CA-S10, and was generally easier on the ears, especially with music played at high level. Christiane Noll's orchestral accompaniments still had a bit of an edge with the GCC-100, but were less annoying than with the CA-S10. (This recording really benefits from the "sweetening" action of the combination of the CAT SL-1 Signature preamp and Audiopax Model 88 tube power amp.) Although the amount of detail presented by the CA-S10 was perhaps even more impressive than that of the GCC-100, listening to the latter was more satisfying in the long run.

The Avantgarde Uno 3.0, while highly revealing of differences in the sounds of components in the system, is not exactly your typical loudspeaker, so I thought it would be worthwhile to try the CA-S10 with a speaker that's more in the mainstream. I remembered that I had a pair of Paradigm Studio/20s in the closet, loaned to me to temporarily expand my home-theater system from 5.1 to 7.1 channels for the review of a surround processor. In his review of this speaker in the February 1998 Stereophile (Vol.21 No.2), Bob Reina had referred to it as being, "by a wide margin, the finest under-$1000/pair speaker I've ever heard." While he might not make the same statement nine years later, the Studio/20 is still a very fine speaker, and its price level represents a good match with the $2000 CA-S10.

The Paradigm Studio/20 is much less sensitive than the Avantgarde Uno 3.0, and, as expected, noise through these speakers with either amplifier was low enough to be inaudible unless I put my ear right up to the baffle. I won't recount all the ways that the Studio/20s sounded different from the Unos; suffice it to say that my conclusion about the differences between the Flying Mole CA-S10 and the PS Audio GCC-100 didn't change: the CA-S10, while impressively detailed in its presentation, was a little too clinical for my taste.

The Flying Mole CA-S10 was a difficult product to evaluate. First, its sound seemed to change during the evaluation period, making it hard to pin down its ultimate sonic character. After a good three months of use, I would assume that the sound quality had plateaued, but it's hard to be absolutely certain. The sound of the CA-S10 was also highly influenced by the choice of interconnect feeding its input, and by the nature of the AC power source, the supposedly superior balanced power resulting in a higher level of noise.

After prolonged break-in, and with AC source and associated equipment optimized as much as possible, the CA-S10 produced sound with an exemplary level of clarity, detail, dynamics, and bass extension. However, I found myself merely admiring these sonic aspects without being fully drawn into the music. While the CA-S10 delivered on Flying Mole's promise of high resolution, the sound also had a clinical, somewhat synthetic quality that tended to keep me at arm's length from the music. Of the CA-S10's class-D output stage, audiophiles who dislike digital amplifiers on principle might very well say, "No wonder—it's digital!" However, I didn't have this reaction to the PS Audio GCC-100, which is also class-D.

These responses may not be shared by everyone. If you place the highest value on an amplifier that delivers the utmost in sonic details, the Flying Mole CA-S10 may be the right one for you, especially if the rest of your system complements its sound. It just didn't float my boat.

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