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Rogers High Fidelity EHF-100 integrated amplifier
I can't imagine what went wrong.
Description
The EHF-100 integrated amplifier ($6350) is one of two products made by Rogers High Fidelity, a new company in rural Warwick, New York. (When I first saw a Rogers amp, at Stereo Exchange in New York City, I assumed the brand name had something to do with the late, lamented Rogers loudspeaker company of Great Britain, but that turned out not to be the case.) Roger Gibboni, who studied engineering at Drexel University and who has over 20 years' experience designing RF circuitry for the military and NASA, founded Rogers High Fidelity in 2009 with an eye to offering very high-quality, US-made tube amplifiers at less-than-extortionate prices.
In contrast with some recent integrated amplifiers, in which power amplifiers are paired with passive front ends, the Rogers EHF-100 has sufficiently high gain to be considered an integrated of the more traditional sort. Here, the majority of voltage gain is provided in the first stage: an EF86 miniature pentode tube. From there, the signal goes to a 12AX7 dual-triode tube, which is used in common-cathode mode to split signal phase for the push-pull output section that follows.
Power tubes in the Rogers amp are KT88s, operated in auto-bias mode: The cathode of each is held above ground by a chunky Dale resistor, ensuring that the KT88's signal grid maintains a steady negative charge relative to the cathode. (I measured approximately 44V across each cathode resistor; consequently, although there was 514V between plate and ground, each KT88 sees a total B+ of only 470V.) The output section of the EHF-100 runs in Ultralinear mode, with plates and screen grids connected to the tapped primaries of very large Hammond output transformers. (I don't know what percentage of primary windings are given over to the screen grid, but other Hammond Ultralinear transformers of my experience are set for 40%.) In addition to its Ultralinear operation, the Rogers EHF-100 also uses a small amount of global feedback. Gibboni says that the amp is fully class-A.
The EHF-100's build quality is excellent—impressively so, given its relative affordability in the context of other US-made tube amplifiers. Every component is hand-wired, most by means of silver-plated hookup wire and thick, clean tag boards. Threaded parts are held in place with Loctite thread sealant and Glyptal red enamel; long runs of cable are tied in place with something very like dental floss (the knots in which also get the Glyptal treatment); and large capacitors are incapacitated with generous dabs of silicone sealant. Solder joins are as close to perfect as I've seen. Parts choices include the aforementioned Hammond transformers (and power-supply choke), plus metal-film signal resistors, polypropylene and silver-mica signal capacitors, Micalex tube sockets, and rhodium-plated copper binding posts from Furutech.
The Rogers EHF-100 offers four pairs of line-level inputs, with one pair of jacks on the front panel—just to the right of the four-position input-selector switch—and the other three on the back panel. A phono section is not provided, although Gibboni says he's considering making one as a standalone component. As with other notable amplifiers, powering up the EHF-100 is done by flipping, in order, two switches: one, Power, to send the requisite voltage to all of the tube filaments; and the other, Operate, to apply the rail voltages. Apart from those and the selector switch, the only other control is a stereo volume pot. (A balance control is not provided.) At the center of the front panel is a power-output meter, calibrated in peak watts from 0 to 100.
The very substantial aluminum-alloy case is finished in what Rogers refers to as an automotive-grade finish, in glossy black (other colors can be had for an additional charge). I love the EHF-100's simple, utilitarian shape; it calls to mind such disparate products as the beautiful Marantz 8B and Shindo Montrachet amplifiers. My only complaints have to do with what seems the amp's excessive size (one thinks of Mary Wollstonecraft Shelley's line "As the minuteness of the parts formed a great hindrance . . . I resolved, contrary to my first intention, to make the being of a gigantic stature") and its disproportionately large, splashy logo and other graphic touches. But that's just me.
Installation and setup
Because my house is only three hours away from the Rogers High Fidelity factory, Roger Gibboni delivered my review sample by automobile, rather than shipping it via brown truck. That said, there was nothing extraordinary about unpacking, installing, or operating the EHF-100—although I was impressed by the exceptional quality of its carton and packing materials. The operating manual was also quite good, and my review sample came packed with a spiral-bound booklet titled "Amplifier Profile": an illustrated collection of reports on tests to which this particular amp had been subjected, including THD vs level, group delay vs frequency, squarewave performance at 1 and 10kHz, and others. I'm told that every Rogers amplifier sold includes such a report.
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Source : stereophile[dot]com
Nordost’s Engaging Comparisons
“The bottom line is, despite the science involved, if you can’t hear it, it matters not,” Nordost’s West Coast distributor Michael Marko told me outside the demo room.
The power cable comparison, performed on a Simaudio Moon CD player connected to a Hegel preamp and monoblocks and Raidho’s X Monitor ($20,000/pair with stands), began with a stock power cable, and shifted to Nordost’s Blue Heaven ($299/2m), the show debut of Red Dawn ($499/2m), Heimdall ($799/2m), Frey ($1899/2m), Valhalla ($2999/2m), and Odin ($16,000/2.5m). Similarly, the interconnect comparison went from generic “cheapie” through maybe a dozen Nordost lines, starting with White Lightning ($179/1m pair) and ending with Odin ($16,000/1m pair).
The resonance control comparison, which covered Nordost’s four models of Sort Kones—from AS (aluminum tip with steel ball, $65 each) to TC (titanium tip with ceramic ball, $350 each)—addressed supports under both the CD player and the power strip on the floor. I recall my own amazement when, years ago, a dealer brought over an early model of Shunyata’s Hydra for me to hear, and how different it sounded when, after listening to it placed directly on the floor, we elevated it on some half decent equipment supports. I often have to remind myself, each time I plug my laptop into my reference system, to stick supports under it, because they greatly improve the sound.
The final comparison, which called into play a NAD DAC with HDMI input, pitted Nordost’s new Blue Heaven HDMI cable ($350/1m) against a stock HDMI cable ($5/1m), Audioquest’s Carbon HDMI ($169/1m) and Diamond HDMI ($1095/1m), and Monster 1 HDMI cable (approx. $40). Need I say that Nordost would not have performed such a comparison in public had it not been sure that its HDMI cable, the only one of the batch, I am told, manufactured entirely in the USA, would come out on top?
Source : stereophile[dot]com
AudioQuest DragonFly USB D/A converter
Thus spoke AudioQuest's Steve Silberman, VP of development, of their brand-new USB D/A converter, the DragonFly. "There are a lot of very good DACs out there," he continued. "There are even a lot of very good affordable DACs. But the problem is, people outside of audio don't want them: They don't want old-style components like that.
"I know a lot of people who have started and sold companies, who could have anything they want. People who love music. And they don't want what our industry makes. For so long, our industry has dictated to the customer: 'You want to play CDs? You need a CD player, and this is how it has to be.' Same thing with DVDs and lots of other things: The manufacturers and the retailers dictate to the customers. I wanted to make a really high-quality audio product that meets people on their own terms."
The product that Silberman and AudioQuest had in mind was an outboard D/A converter that would sell for the same price as an Apple iPod Classic: a mere $249. The AudioQuest DragonFly measures 2.5" long, weighs three-quarters of an ounce, streams up to 24 bits and 96kHz, and plugs directly into the user's laptop or desktop computer. And it's a heck of a thing.
Description
Ideas in mind, Steve Silberman approached Gordon Rankin, the man who created what many of us regard as high-end audio's first USB D/A converter: the Wavelength Audio Crimson. The Crimson, which went on sale in 2004, wasn't Rankin's only computer-audio first. He also invented the first cross-platform asynchronous USB protocol, which allows the clock in an outboard DAC to override the clock in the datastream coming from the computer—the native frequencies of which are mathematically unrelated to audio sampling rates, to near-catastrophic effect in terms of timing errors, or jitter. Rankin has since licensed that code, given the trade name Streamlength, to a number of well-known manufacturers, and it now resides in the ROMs of many computer-audio components that have received glowing reviews in Stereophile.
The Streamlength software resides on the Texas Instruments TAS1020 controller board inside the DragonFly: one of three chips at the heart of the new converter. Rankin, who designed every aspect of the DragonFly except its connectors and cosmetics, says that AudioQuest expressed admiration for the Wavelength Proton D/A converter ($900; see my review in the October 2011 issue). Thus he began by basing a prototype on the Proton's Wolfson D/A chip. "I got it working," Rankin says, "but, for me, there was something lacking. I asked [AudioQuest] to let me do whatever I wanted, and so I ended up using the 24-bit ESS Sabre DAC." A Burr-Brown headphone amp/line amp, incorporating a 64-step analog volume control, completes the picture.
Rankin seems almost surprised at how well the finished DragonFly turned out—but he adds, with a laugh, "You don't know how much of a pain in the ass it was to get it that small! There are 107 parts inside, including five regulated power supplies." The scale of the thing's innards are typified, Rankin says, by the 1mm microdot LEDs that enable the dragonfly emblem on the DAC's zinc-alloy case to change color in accordance with the sampling rate of the file being played: green for 44.1kHz, blue for 48kHz, amber for 88.2kHz, and magneta for 96kHz. Yet for all that, the DragonFly is made in the USA.
Last but not least, the DragonFly's connectors are the sorts of things one might expect from a maker of perfectionist-quality cables: Its 3.5mm jack and USB plug feature silver-plated contacts. is machined from a compound of copper and beryllium (the latter said to add strength and elasticity), while the USB pins are copper. Both connectors undergo AudioQuest's direct-silver plating.
Installation and Setup
Installing the AudioQuest DragonFly, which is designed to work with the latest versions of Microsoft Windows and Apple OS X, took a little less than 15 minutes. Physical installation consisted simply of plugging the unit's integral USB plug into an available jack on the back of my Apple iMac and fitting the 3.5mm jack at the DragonFly's other end with an appropriate audio cable (about which I'll say more in a moment). Finishing the job was a simple matter of clicking on the Mac's Systems Preferences window (footnote 1), clicking the Sound icon, and then, under the Output tab, selecting "AudioQuest DragonFly," which appeared there as if by magic. (Under the Sound Effects tab I selected Internal Speakers, thus denying myself the pleasure of using a five-figure music system to alert me to every new kitten photo on Facebook.)
I mentioned the DragonFly's 3.5mm output jack, which might pose a challenge to The Unprepared. I still have a mini-plug-to-phono-jack adapter left over from my days as a Sony Walkman Pro owner, but I didn't press it into service. Rather, I accepted the loan, also from AudioQuest, of one of their new single-run Bridges & Falls interconnects. The interconnect cable I borrowed is a 5m run of AudioQuest Yosemite, with a 3.5mm plug of silver-plated "red" copper at one end, a pair of RCA plugs of the same composition at the other end, perfect-surface copper+ conductors, fluoropolymer air-tube dielectrics, and AudioQuest's 72V dielectric bias system: a sophisticated cable by anyone's definition. The retail value of this 5m Yosemite cable—the second-most-expensive in the Bridges & Falls line—is $1395. (I'm cheered by the existence, at the other end of the range, of the Evergreen single-run cable, which would sell for $53 for this configuration and length. I look forward to trying it.)
I've used a few different Mac-based music players in recent months, with still more on my to-do list. My reference remains Decibel v.1.0.2, by Stephen F. Booth Software, but rest assured—there are more than just one or two very good players out there. If you're still using iTunes, you're not getting the performance of which your system is capable, plain and simple.
Footnote 1: My iMac runs OS X 10.6.8.
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Source : stereophile[dot]com
