| Jeff Rowland Design Model 2 + BPS-2 Stereo Amplifier  - Robert Deutsch reporting in Stereophile Aug'95 - I remember having a conversation with an audiophile some time ago about the thorny subject of choosing an amplifier. He was convinced, on the basis of an article he had read in Stereo Review, that all amplifiers of a given power rating sound pretty much the same. Although he was sufficiently well off to buy just about anything on the market, he didn't want to waste his money. He chose the amplifier for his system by going through the Audio Annual Directory Issue, calculating the price:watt ratio for each amplifier that was listed, and then bought the amplifier with the lowest price/watt figure that had enough power to drive his speakers. He didn't do any comparative listening and didn't consider buying anything that cost more for the same power, because he knew already that it wouldn't sound any different. The memory of that conversation came back to me after a recent chat with another audiophile, who had heard that I had a Rowland (footnote 1) Model 2 for review and asked me if I didn't think the Rowland was too expensive for its power output. The Stereophile Reviewer's Oath made me bite my tongue [the Oath has been responsible for a lot of chewed-up tongues], and I told him that he'd just have to wait for the published review to find out what I think of the Rowland Model 2. How do you define value in an audio component? For an amplifier, power output is obviously important, but it's not the only criterion; otherwise, we'd all be selecting our amplifiers strictly by price:watt ratios. The Rowland Model 2's $5800 for 75W puts it above the 95th percentile of amplifier price:watt ratios (footnote 2), although it's the least expensive amplifier from Rowland. Is it worth the money? Can you get sound that's as good or better from amplifiers that cost much less? Is this review going to provide the answers, or are these merely rhetorical questions? Description & Design Smallish, very heavy for its size, with classic proportions, and impeccably finished. Beauty, of course, is in the eye of the beholder, but in this beholder's eye, the Rowland Model 2 is one beautiful piece of equipment. Everything about it says quality. All chassis components, including the ¾"-thick front panel, are made of machined aluminum alloy; fit'n'finish are second to none. Dimensional accuracies are said to be held to within 0.005" tolerance; dimensional ratios are designed to be "golden mean" nondivisible, and the size of each cooling fin is non-harmonically related to the adjacent fin.  The construction of the Model 2 reveals an almost fanatical devotion to resonance control. The two toroidal power transformers are enclosed within a machined-aluminum tube, which is physically isolated via large Neoprene O-rings and sandwiched between two machined subchassis structures spanning the entire length of the amplifier. Power-supply capacitors are rigidly clamped to the subchassis. The critical audio circuitry is contained in plug-in potted modules, which are themselves clamped in place by aluminum bars. The top panel fits the chassis exactly and is held firmly in place by a set of bolts/washers. Finally, Rowland provides both machined metal cones and Sorbothane discs for a choice of coupling or decoupling support. (I used the metal cones.) The effect of all this resonance control is obvious when you tap or knock on the amplifier: all you get is a very dull thud (and sore knuckles). Both the front and the rear of the amplifier have clear, uncluttered layouts. The front panel has only an illuminated power button (no meters or flashing LEDs, thank you very much), which switches between Operate and Standby.  The rear is dominated by a 1.5"-diameter fitting that looks as though it's for hooking up a central vac. In fact, it's the socket for the cable that will connect the Model 2 to the optional battery power supply (to be available this summer). The Model 2 has XLR balanced inputs only, but Rowland provides a neat pair of XLR-to-RCA adaptors; the Model 2 can be driven balanced or unbalanced. (Rowland follows the convention of having pin 3 on the XLR connector as positive so that comparisons with equipment having the more common, ANSI-standard, pin-2-positive assignment involved reversing the absolute phase to compensate.) One toggle switch allows for selection of low-impedance (600 ohm) or high-impedance (36k ohm) operation; another the choice of 26dB or 32dB gain. I used the Model 2 with the high-impedance, low-gain settings. The rest of the space on the rear panel is taken up by a single pair of Cardas binding posts (they have enough clearance to allow biwiring), a socket for the optional remote control, an IEC 320 socket (for a heavy-duty 20 amp power cord), and an AC fuse. Jeff Rowland was one of the first audio designers to tout the benefits of fully balanced (differential) circuitry; needless to say, the Model 2 is not one of those amps that has balanced inputs but whose circuit topology is actually unbalanced. A fully balanced design like Rowland's requires essentially double the components of an unbalanced design; this is undoubtedly part of the reason for the Model 2's cost. The circuit topology is of the current-feedback rather than the more common voltage-feedback type; an approach that, according to Rowland, offers wider bandwidth, very fast settling time, and low distortion at all frequencies. The output section features four individually selected bipolar transistors per phase per channel, totaling 16 transistors overall. A sophisticated temperature-sensing circuit optimizes bias. The Model 2's output stage operates in class-AB rather than class-A. Jeff Rowland believes that a well-designed class-AB design can perform as well as a class-A, without the penalty of high power consumption and heat generation. In common with many high-end amplifiers, the Model 2 has no overall loop feedback. All amplifiers have transformers in the power supply, and tube amplifiers have transformers on the output side (except, of course, if they're the output-transformer-less variety); the Rowland Model 2 is unusual in having transformers in the signal path on the input side. The input transformer features proprietary winding techniques and high-percentage nickel core materials. The claimed advantages of using an input signal transformer include total isolation of ground currents, effective RFI filtering, pure resistive loading, response bandwidth to 200kHz, a common-mode rejection ratio (CMRR) greater than 60dB at 20kHz, extremely low distortion (±0.01% at 20Hz), and insensitivity to a wide range of source impedances.  The power supply itself features toroidal transformers with lower flux density than conventional designs (1.5 Tesla at 50Hz, if you must know); 260,000µF capacitance; and separate regulated positive/negative supplies for input, output, and "housekeeping" functions. Rowland points out that the advantages of balanced operation include a 50% reduction in power-supply voltage, which permits more reliable high-speed operation. Sound One of the problems in reviewing audio equipment is that it's sometimes difficult to be sure of the extent to which the "sound" of a particular component represents an interaction between the component and the rest of the system, rather than being the sound of the component per se. To guard against errors of this sort, it's important to use matching components that are as neutral and accurate as possible so that deviations from the absolute sound can be attributed to the Device Under Test. Still, if an amplifier being tested is disappointing, one wonders if it would have performed better with a different set of associated equipment (footnote 3), or if one found the right tweak that would allow it to sing. Of course, if an unfavorable interaction is suspected, the reviewer will try swapping components, changing cables, and tweaking the setup, but there's a practical limit to this, and one can question whether the typical consumer should be expected to follow this path. (Actually, my feeling is that, if a component needs to have everything tweaked to a fare-thee-well, there's something wrong with the design.) From the reviewer's perspective, the best situation is one in which the component sounds so good right off the bat that there's little or no need for tweaking or substitution of components. This was the case with the Rowland Model 2. Listening to track 3 of the first Chesky Jazz Sampler with the Model 2 in the system for the first time (after a few hours' warm-up), my immediate impression was of a level of detail and transparency that went beyond anything I had heard previously in my system. It was an impression that was to persist throughout the extended evaluation period. Now, it may be that I happened to hit on a particularly synergistic system interaction (Rowland and Dunlavy are both located in Colorado Springs, so it could have something to do with that mountain air), but I wasn't about to search for components that would make the Model 2 sound worse! In any case, my impression of the Rowland Model 2 was the same with any of the three preamps, two D/A processors, and the two sets of loudspeaker cables that were part of the system at one time or another. I also know that it wasn't a matter of the Model 2 somehow compensating for loudspeaker colorations: the Dunlavy SC-IV is as neutral and accurate as just about any speaker out there, with a linearity of impedance, amplitude, and phase response that makes it ideal for identifying the sound of other components, especially amplifiers. Rowland electronics have had a reputation for sounding "dark," with a top end on the soft side of neutral. A couple of years ago I had a sample of the Rowland Consonance preamp to compare with some preamps I was reviewing; although I liked the Consonance quite a lot, I thought it did sound a bit soft and forgiving. The Model 2 represented a distinct change from the traditional "Rowland Sound." The top sounded open and extended, while maintaining exceptional freedom from the "electronic" quality that is the bane of solid-state amplifiers. With the right source, like one of the Reference Recordings HDCD releases played through the HDCD-equipped Sonic Frontiers SFD-2 Mk.II, instruments with significant treble energy were reproduced with crispness as well as delicacy. Throughout the entire range, but especially in the highs, the Model 2 had stunning transparency, providing resolution of detail but adding little sound of its own. In fact, the aspect of the Model 2's performance that impressed me the most was its resolution. Parts of the sonic landscape that were slightly obscured with other amplifiers were clear and distinct through the Model 2. Depth and ambience seemed to be limited mostly by the recording itself. Through the Model 2, I could also easily hear the sonic effects of changes in associated equipment, such as the superiority of the Mk.II version of the Sonic Frontiers SFD-2 over the original. Two areas of performance where moderately powered amplifiers are often thought to be compromised are dynamics and bass extension. The Krell KSA-100S certainly suffers in these areas compared to its more powerful KSA-300S stablemate. I didn't have a chance to compare the Rowland Model 2 with the more powerful Rowland amplifiers; however, the Model 2's dynamic liveliness and firmness of bass response made it easily competitive with the various other high-powered amplifiers I had on hand. My usual bass-and-dynamics torture test, Mickey Hart's Planet Drum (Rykodisc RC-10206), was reproduced with a high "startle factor," the bass shaking the floor in a manner that was only marginally less convincing than when using a high-powered bass champ like the Bryston 7B. Although I no longer had the Krell KSA-100S around for direct comparison, my recollection was that the Krell, which is rated at 100W, was less dynamic and had subjectively less impressive bass response than the 75W Rowland (footnote 4). The quality of the bass was excellent: tight and tuneful. In terms of sheer volume, the Rowland Model 2 had no trouble driving the Dunlavy SC-IVs to any level that I found tolerable. At levels that I found intolerable (peaks of 103dB, "C"-weighting, on the Radio Shack meter, which is known to underestimate short-term peaks by about 6dB), the Bryston 7Bs and the Carver Lightstar Reference did sound more effortless, but this was apparent only in direct comparison. In normal listening, I never felt the need for more power. I should note, however, that my listening room is small, and the Dunlavy SC-IVs have a 91dB sensitivity. Those with large listening rooms and insensitive speakers may not be satisfied with the Model 2's 75W. The Rowland Model 6 monoblocks, with their 150W/channel output, would likely be more suitable in these situations (footnote 5). Shoot it out My formal listening to the Rowland Model 2 concluded with a three-way shootout: matched-level comparisons (peak spls around 90dB) among the Model 2, the Threshold T-200, and the Carver Lightstar (reviewed in Vol.18 No.4. and Vol.18 No.5, respectively). For a test piece I used Sylvia McNair's recording of what has been called the best American popular song ever written: Kern and Hammerstein's "All the Things You Are" (from Sure Thing: The Jerome Kern Song Book, Philips 442 129-2). For this comparison, rather than concentrating on detail, imaging, depth, bass extension, ambience, etc., I just allowed the sound to wash over me, and I used the extent of my involvement in the music as an overall indicator of the system's effectiveness in creating an illusion of reality (footnote 6). I have a lot of respect for both the Threshold T-200 and the Carver Lightstar; I'm particularly fond of the Threshold, which I had thought worthy of a Class A "Recommended Components" rating (Vol.18 No.4). Nevertheless, in the head-to-head comparisons, my preference overall was for the Rowland Model 2. With the Rowland amp in the system, the illusion of the presence of Sylvia McNair's voice in the room was just a bit more convincing; I had to do less work of imagination to pretend that I was listening to a real singer and real instruments rather than an electro-mechanical contrivance. Conclusion So, does the Rowland Model 2 offer good value? Can you get sound that's just as good from amplifiers that cost much less than its $5800? Ultimately, answering these questions with any confidence would require familiarity with every amplifier on the market as well as knowledge of what's important to the individual audiophile. I possess neither, but I set myself up to answer these questions, so I'd better at least take a stab at it. Given today's high-end audio marketplace, and assuming an audiophile ethos that finds it acceptable to spend large amounts of money for what are arguably small sonic improvements, I think the Rowland Model 2 does represent good value. By a small but significant margin it's the best, most natural-sounding amplifier I've had a chance to evaluate. The battery power supply that's about to become available (which I will report on in due course) promises further improvement. Can the Rowland Model 2's sound quality be matched or exceeded for less? This is a really tough, even impossible-to-answer, question. There are a lot of amplifiers out there, with new ones being introduced all the time. You can get very good sound from amplifiers that cost much less (you'll find some of them listed in Stereophile's Class B of "Recommended Components"), and if you have insensitive speakers that you like to play loud in a large listening room, the Rowland Model 2 clearly would not be your best choice. However, power considerations aside, I can't think of a less expensive amplifier that fully matches the Model 2's collection of sonic virtues. It's the kind of amplifier that, in the right system, is likely to make you forget about amplifiers and just listen to the music. Footnote 1: Thankfully, the Rowland Design Group is still headed by Jeff Rowland, so we don't have to go through that "Are we talking about the Man or the Corporation" nonsense (cf Mark Levinson, Carver). Footnote 2: The percentile estimate is just a guess. I didn't plot a frequency distribution of price:watt ratios. After all, this is just an intro. Anyway, price:dBW ratios would be more meaningful but still misleading. Footnote 3: Given a negative review, Standard Manufacturer's Comment No.2 is: "It's obvious that our product allowed the reviewer to hear, for the first time, the colorations of his system." Footnote 4: Of course, the difference between 100W and 75W is only 1.25dB. Footnote 5: Although you have to look closely at each amplifier to tell the difference between the Model 2 and a single Model 6 monoblock, the Model 6 is not just a bridged Model 2. In fact, the Model 2 cannot be bridged for mono operation (it's already bridged); but, with suitable adapters, a pair of Model 2s could be used in a biamped setup. Footnote 6: I listened to each amplifier several times, varying the order of presentation, and used the Sonic Frontiers SFD-2's polarity-reversal switch to compensate for the different XLR pin assignment conventions (pin-3 positive for Rowland, pin-2 positive for Threshold and Carver). - RD wrote again about the Model 2 in Dec'95 - In my four years of doing equipment reviews for Stereophile, I've had in my listening room, for varying periods, tube amplifiers from Audio Research, Sonic Frontiers, Luxman, VTL, Cary, Audion, Conrad-Johnson, and Quicksilver. Some had the "magic" (tubeophiles will know what I mean) but were deficient in other ways: insufficient power to drive most speakers to realistic levels, weaknesses at the frequency extremes, etc. Others had lots of power and wideband frequency response, but were missing the magic. What is this "magic"? Simply, it's the ability to avoid sounding like an amplifier, an absence of "electronic" sound... Of the solid-state amplifiers I've listened to at any length, the one I've found to have the least amplifier sound was the Rowland Model 2 (reviewed in Vol.18 No.8). This is the amp I used for explicit comparison with the Balanced Audio Technology VK-60. Like the VK-60, the Rowland Model 2 is a fully balanced design, but it uses different XLR pin-assignment conventions (pin-3 positive for the Rowland, pin-2 positive for BAT), which means that the two amps' absolute polarity is reversed, a problem easily corrected by use of the Sonic Frontiers digital processor's polarity reversal feature. The Model 2's rated 75Wpc puts its power output just 1dB higher than the VK-60, and the $5800 price is correspondingly higher. When I started the Rowland/BAT comparison, I hadn't listened to the Rowland Model 2 for at least a couple of months. Firing it up again, I was quickly reminded why I'd been so enthusiastic about this amplifier in the review. It is a truly excellent amplifier, worthy of Class A status. I required several back-and-forth changes between the Rowland Model 2 and the BAT VK-60 to identify their differences. The comparison between the amplifiers confirmed that the VK-60 is quite special when it comes to harmonic accuracy. The Rowland Model 2 is no slouch in this area; in fact, its preservation of the natural timbre of instruments and voices outpoints any other solid-state amplifier of my experience. Still, whenever I switched over to the BAT VK-60 (matching levels, and remembering to reverse absolute polarity), a layer of artificiality was removed, and I came closer to feeling that I was listening to the real thing. Also, although the depth of the soundstage with the two amplifiers was comparable (with the right recordings, very deep), the VK-60 evinced superior three-dimensionality of images within the soundstage. Thus the trombone solo in "Winter Wonderland" (Big Band Basie, track 13) seemed to have a more rounded physical presence, and there was greater differentiation of the individual voices that make up the Turtle Creek Chorale in Postcards (Reference RR-61CD). Well-designed solid-state amps tend to have better bass responses than tube amps; indeed, this was an area in which the Rowland Model 2 was superior to the BAT VK-60. However, the differences weren't as great as one might expect. With my usual torture-test, Mickey Hart's Planet Drum (Rykodisc RCD 10206), the bass from the VK-60 was actually quite impressive: deep and well-controlled, with perhaps just a bit of added warmth, but a far cry from the warm-and-woolly bass that characterizes so many tube amplifiers. Only when I switched over to the Rowland Model 2 was I reminded that the Dunlavy SC-IVs are capable of even better extreme-low-end performance. For those with speakers whose bass responses doesn't go much below 30Hz, the point is academic. For those with speakers that have subwoofing capability and who like to play music that tests that capability, the Rowland Model 2 might well be a better choice. - RD returned to the Model 2 in Jun'96 - To get a handle on the YBA 1 Alpha HC's performance in comparative terms, I spent a lot of time switching back and forth between it and the Jeff Rowland Design Group Model 2. In many ways, these amps are natural peers/competitors. They have similar power ratings (Rowland, 75Wpc; YBA, 85Wpc); they're in roughly the same price range (Rowland, $5800; YBA, $7000); they're both small but heavy; and both represent their designers' at-times-fanatical pursuit of the twin goals of accuracy and musicality. The Rowland Model 2 is firmly established as a Stereophile Class A Recommended Component. When I reviewed it in 1995 (Vol.18 No.8), I thought it was "by a small but significant margin, the best-sounding amplifier I've had a chance to evaluate," a statement that I would still stand by now, but I would add "solid-state" before "amplifier." (In some respects, I prefer the tube-based Balanced Audio Technology VK-60 to the Rowland Model 2.) Although the YBA 1 and the Rowland Model 2 have certain sonic similarities, both are superb by almost any standard. Listening comparisons revealed that each amplifier has a distinctive character. I've already commented that the Rowland evinced better bass performance (at least when driving the Dunlavy SC-IVs); it also had a somewhat more incisive and dynamic sound, the YBA 1 sounding a bit more polite or laid-back in comparison. Several times, after switching from the YBA to the Rowland, having matched levels at 1kHz and corrected for absolute polarity, I thought that the music played through the Rowland was louder. Each time, I rechecked the test signal voltage at the amplifier terminals, and confirmed that it was within 0.1dB of the YBA, even on the low side (eg, YBA, 1.207V; Rowland, 1.197V). The Rowland seemed ever-so-slightly more forward than the YBA, with a subjectively more extended top end that gave percussion instruments, especially cymbals and bells, greater presence. Is the YBA, in its pursuit of a grainless upper midrange, "shaving off" some information, or is the Rowland adding grain that emphasizes detail? Tough call. If the measured performance of the YBA 1, like that of the Rowland Model 2, is beyond reproach, as I suspect it is, the answer is not going to be found there, so we're back to listening to recordings. Do we, can we, know what a given recording really sounds like? I don't think so. Every recording has to be listened to on some kind of system, and every microphone has sonic characteristics that are apparent only when you listen to the sound it produces through an amplifier and speakers, each with their own sonic characteristics. What I can say is that with some recordings, like most Dorian, Chesky, and Reference Recordings releases, the sound of the Rowland Model 2 was more exciting and involving than that of the YBA 1. With others, such as the typical multimiked efforts from nonaudiophile companies, the YBA 1 allowed for a more relaxed, less in-your-face listening experience. It was not a matter of the YBA 1 being less revealing, but rather a matter of what it was revealing, which was, if you like, a "kinder, gentler" sonic world. - RD added the BPS-2 battery ps in Jul'97 - Like many audiophiles, I've been impressed with the effectiveness of dedicated AC lines and line conditioners. Although power supplies in audio equipment are supposed to provide isolation from the various sorts of interference (EMI and RFI) that may be present on AC, cleaner AC power usually translates to cleaner sound. If reducing EMI/RFI from the power source is worthwhile, it follows that eliminating it should be even better (footnote 1). This is the promise of battery power: by having a source of pure DC, you are, in effect, rolling your own. No EMI/RFI coming in through the power line, and you don't have to worry about the line-voltage variations that are common in most areas of North America. But wait, there's more! According to Jeff Rowland, conventional AC-based power supplies in amplifiers suffer from impedance fluctuations that are a byproduct of the conversion from AC to DC. This, in turn, results in ripples in the DC supply, particularly evident at low frequencies. With a battery supply, the AC/DC conversion is performed by the charger, so the battery may be thought of as a capacitor with high current capability, low DC resistance, and no AC ripple. Of course, battery power is not without its downside. First, there's the cost: batteries that produce sufficient voltage and current to run a power amplifier are likely to be expensive. The service life of a lead-acid battery can be reduced by too much or too rapid charging, and by allowing the battery to discharge completely before charging. (NiCads, on the other hand, must be completely discharged before recharging.) The battery's power reserve has to be sufficient to last at least the average listening session, so we're not just talking about using a couple of AAs. Audio circuits are sensitive to voltage drop, so to maintain sound quality the batteries' output must be monitored, and provision made for switching from DC to AC if the need arises (assuming that the amplifier has an AC as well as a DC power supply). Over the years, a number of high-end designers have introduced battery-powered products, but to my knowledge none has taken the uncompromising approach of Jeff Rowland.  The BPS-2 weighs over 50 lbs and contains six 6V, 12 ampere-hour, maintenance-free Sealed Lead Calcium (SLC) batteries, as well as a microprocessor-controlled circuit that monitors electrical parameters and provides charging to keep the batteries in peak operating condition. Charging is ripple-filtered, which smooths out the charging pulses that would otherwise result in mini-charge/discharge cycles, thus shortening service life. Unlike NiCads, SLCs don't suffer from the "memory" phenomenon; and, unlike lead-acid automobile batteries, they're not damaged by prolonged discharge. The batteries' expected lifetime is six to eight years of normal use, with the replacement cost currently about $400. Although the Jeff Rowland's Model 2 amplifier was initially available only with AC power, the battery power supply is clearly not an afterthought. From the time they were first manufactured, all Model 2s have been equipped with a large connector in the back that allows connection to the BPS-2 via a thick cable (made by Cardas).  The units are meant to be stacked, the BPS-2 providing a high-mass base for the Model 2, and have the usual impeccable Rowland fit'n'finish. Ergonomically, the Model 2/BPS-2 combination was a dream to operate, with no operational glitches. Pressing a button on the BPS-2's front panel toggles between AC and battery (DC) supply, with a small light indicating whether the BPS-2 has been sufficiently charged. If the BPS-2 isn't ready, then pressing the button has no effect, the Model 2 continuing to operate from AC. The changeover from AC to DC power was accomplished without switching noise or any interruption of the sound. When connected to a fully charged BPS-2, the Model 2 will operate for several hours without being connected to AC (playing music at moderate level, I got over four hours before the red warning light came on), although Rowland recommends that it be left plugged in. This was the way I used it most of the time. (But see below.) Promise fulfilled? Upon receiving the Model 2/BPS-2 combination (and after a suitable break-in period), my first task was to get my ears accustomed again to the Model 2 in its normal AC-powered mode. Much of the associated equipment in my system has changed since the original review, but my opinion of the Model 2 hasn't: I still think it's a superb amplifier, refined yet dynamic. On changing over to battery power, initial impressions were equivocal. Switching back and forth, replaying the same segments of music (with the preamp gain control untouched, volume remains the same), I first had a hard time detecting any change. Eventually I was able to get a fix on some differences, but they were generally minor. In the battery-powered mode, the bass was a bit leaner and tighter, although not more extended. (The Model 2 has very good overall bass performance, but it's no match for a bass champ like the Bryston 7B-ST.) The upper midrange/treble was slightly cleaner, more delicate, with transients ringing more freely, but this was apparent only in the most critical comparisons. The magnitude of the differences was less than I've heard among high-quality interconnects or speaker cables. The effect on dynamics was complex. At very high levels, louder than I normally play my system, I thought the battery mode was somewhat reticent, with not as much get-up-and-go as AC operation. At more sensible levels, however, the dynamic life of the music was enhanced by the battery mode, with a better sense of rhythm and pace. Once again, the differences were subtle, evident only on repeated comparisons. Not fair? I made these comparisons with a Chang Lightspeed CLS 9600 power-line conditioner and a dedicated AC line. While this sort of setup is not uncharacteristic of the kind of high-end system in which the Model 2 is likely to be found, it's arguably not the fairest set of control conditions under which to assess the benefits of battery power. In any case, it would be useful to know how battery power compares with "raw" AC. To do this, I repeated the AC/DC comparisons with the Model 2 plugged directly into the wall, without going through the Chang power line conditioner, but still using the dedicated AC line. Results: still pretty close, but the differences were a bit more clearly in the favor of battery power, the AC condition sounding somewhat fuzzy and subdued. Finally, I plugged the Model 2 into a nondedicated AC line. This time it was no contest: In the battery mode, the sound had greater openness and transparency, with a greater "suddenness" of transients. The percussion instruments on track 3 of the familiar Chesky Jazz Sampler & Audiophile Test CD (JD37) actually seemed louder, the music having a more dynamic feel, and the soundstage was more precisely defined. By ordinary standards, the sound in the AC mode was quite acceptable; but, having heard the difference, I was eager to switch back to battery operation. Oh, just one more thing... Although the BPS-2 is designed to be left plugged in all the time, I would not have been true to the obsessive-compulsiveness that characterizes all audiophiles had I not bothered to check whether the sound improved when the BPS-2 was unplugged from AC. The part of me that's not obsessive-compulsive would dearly like to report that this makes no difference, but I must say that it does. Not night-and-day, not chalk-and-cheese, but another subtle improvement that moves the sound away from the electronic and toward the musical. Having to unplug the BPS-2 is a pain, and remembering to re-plug it at the end of the listening session is even more so, but a man's gotta do what a man's gotta do. So, is battery power worth it? At $5800, the Jeff Rowland Model 2 is an expensive amplifier, and the additional $2600 for the BPS-2 is not exactly small change. Is this a cost-effective way to improve the sound of a system? Tough question. It depends (my favorite way to start answering difficult questions) on a number of factors, especially the nature of the system itself.  There's no doubt in my mind that the BPS-2 "works". Under certain conditions, it allows the Model 2 to operate in a manner that results in a more musically satisfying listening experience. However, the effect is greatest when the amplifier is not given ancillary support through use of a power-line conditioner and a dedicated AC line. Chances are, if you can afford $5800 for an amplifier, you're likely to have a listening room supplied with dedicated AC lines, and if you don't, you should. The cost of a good power-line conditioner and the installation of dedicated lines is considerably less than the price of the BPS-2, and will benefit the entire system. Using the appropriate AC power-line treatment gets the sound pretty close, albeit not all the way to that obtainable through battery power. Unless everything else in the system is beyond reproach, I'd be inclined to spend the $2600 on a component that offers a greater potential for improvement. - review by Robert Deutsch in Stereophile - AllegroSound (Est.1973) Los Angeles, California USA Rick@AllegroSound.com 
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