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Tuesday, June 26, 2012

Audiophile Amplifier Review!
Rogue Audio Medusa Digital/Tube Amplifier:
Modern Hybrid Improves Amplifier Accuracy


Price: $3,995
Like: ultra-accurate, smooth sound
Dislike: can't see logo on black version
More info: Rogue Audio Medusa
by John Gatski

  Although digital technology and innovative design have permeated the high-end audio niche for decades with CD players, SACD/DVD-A players, digital downloads, etc., amplification has remained largely analog. Strides in power supply efficiency have been made, but the heart of amplifiers still work as they have for years with varying twists on bipolar or MOSFET output.
  Early digital amps were detailed and tightened up the bottom end, but were often characterized as sharp, harsh and edgy (full of ear grit as I would say). Over the last few years, however, great strides in digital amplifier technology have resulted in improved detail, bass speed and realism, but also smoothing out the grainy, hard edge of previous generations of digital amps.
  One example of this new class of digital amplifiers is Rogue Audio’s Medusa. Who would have thought that a company that had exclusively designed traditional tube amps and preamps would come up with a digital/analog hybrid that is so breathtakingly accurate. Yet the amp is under $4,000 and still made-in-the USA.

  The Rogue Audio Medusa is a 200-wpc, hybrid digital amplifier, utilizing a tube input stage, three-stage analog power supply and a Class-D output stage utilizing Hypex digital modules with MOSFET output. According to chief designer and company president Mark O’Brien, the hybrid design offers the smoothness of tubes, but with the bass speed and accuracy of the best solid state. 
  O’Brien noted that he does not use the Class D modules as is, but the circuit is extensively modified to get the best sound possible. Much of the module is bypassed in favor of the custom, proprietary Rogue Audio design, he explained. The two 12AU7s hand-selected signal tubes serve as the phase inverter and internal front gain stages.
  O’Brien noted that three massive linear power supplies are used to power the amplifier circuitry and ultra-high quality parts are used extensively throughout the design.
  The Rogue Audio digital hybrid amps are available in two power configurations: the 100 watts per channel Hydra ($2,995) and the reviewed Medusa at 200 watts per channel ($3,995). They also come in black or the tinted silver finish that Rogue often uses. its hard to see the Rogue logo on the black version.
  The Medusa’s stereo input connection options include fully balanced XLR, or unbalanced single-end RCA, and the speaker outputs are five-way binding posts. 
An IEC power cord connection rounds out the back panel.

The hybrid tube/Class D digital Rogue Audio Medusa is one of the best amplifiers I have auditioned. It renders a very accurate soundstage with tight bass and a very layered top end that matches or exceeds much more expensive analog amps.

  The front panel is simply the power switch and the standby/normal/fault operation LEDs. Overall, the look is quite attractive in its Rogue Audio, minimalist family resemblance. The anodized silver pigment hue is slightly darker than past Rogue products, but it looks and feels way more expensive than its list price would suggest.
  Although the amp is part digital, it is not a lightweight. It still weighs in at just under 40 pounds, with most of the heft in the power supplies and sturdy chassis. The manual is pretty basic and measured performance specs are sparse; only distortion and output power. No slew rate, damping factor or power draw numbers are cited.

The setup
  I installed the Rogue Audio Medusa in my main listening room. Speakers included Legacy Focus 20/20s, Legacy Studios HDs, Paradigm Signature S8s and a set of Westlake Lc2.65 two-ways. I mated the Medusa with several preamps including my all-tube Rogue Audio 99 Magnum (6SN7 tubes), Pass Labs XP-10 MOSFET preamp, and my trusty Legacy/Coda high-current solid state output preamp.
  Source material was mostly high resolution and included music Blu-rays, DVD-As, SACDs, HD Tracks and ITRAX digital downloads, and my own 24-bit recordings of acoustic and jazz guitar. Players included the Oppo BDP-95 universal player, and an Esoteric DV-50 DVD-A/SACD player.

Medusa's Digital Modules

  To test my theory that the Medusa design would be superb for LP listening, I also listened to a number of high quality LPs via a Marantz TT-15 equipped with an Audio-Technica AT150ML cartridge, using the Pass Labs XP-15 phono preamp.
  All line and speaker connections were made using Alpha-Core Goertz silver cables. All components were plugged into the AC using an Essential Sound Products Essence power strip and Essence AC cables.
**After connection to the initial system, I let the Rogue burn in for three days and then commenced extensive listening sessions through the various sources and speaker options.

The audition
  As soon as I started listening to the Medusa through the Legacy Focus, I immediately noticed the tight bass. The bottom-end speed and precision made my reference Anthony Wilson Trio - Our Gang SACD sound extraordinary. On tube amps, the Legacys can be a bit plump, but the Rogue Medusa hybrid output projects this as clean as I’ve ever heard this jazz guitar/organ/drums recording. Yet the extension and fullness of the recording were there — like a well-setup live recording. Via the Medusa, the drum cymbals were unveiled — sharp, but not harsh, transient response that sounded natural with precise width and depth. When the bass is properly proportioned the treble and midrange are easier to wrap your ears around.

 The Rogue Audio Medusa is a 200-wpc, hybrid digital amplifier, utilizing a tube input stage, three-stage analog power supply and a Class-D output stage utilizing Hypex digital modules with MOSFET output.

  As I went through disc after disc and download after download, the Rogue never sounded thin or edgy. It is one of the few digital amps that I have liked (loved?) in my system. Even overly dense dance/pop music sounded damn good on this amp; usually, a no-no with traditional tube amps.
  Those of you who like your classical music through tube gear, will not be let down by the Medusa, in fact, the balanced sonic presentation will allow you to hear detail you may have never noticed — especially during the full power of a symphony. Violin harmonics, and the deep, yet tight wrapped tympani are much more life like on the Medusa than most tube amps I have owned or auditioned. A good example of this was the Popov - Symphony No. 1 Op. 7 - Leonard Botstein with the London Symphony Orchestra (Telarc). On either the Paradigms or the big Legacy Studios, when called for, this recording was conveyed with authority and sweetness.
  On my own live-to-stereo 24-bit PCM and DSD recordings played back through a TASCAM DVRA1000-HD professional deck, my Martin and Gibson guitar recordings were clear and concise, yet the width of the stereo image was deep and wide. The solid rosewood and spruce top acoustic guitar’s sonic signature was spot on — with that plucked presence you get from strumming new phosphor bronze strings. The Rogue Medusa is very natural sounding with acoustic instruments.

  Versus my $6,000 Bryston 14B-SST amp, the midbass seemed slightly tighter on the Rogue with the big Legacy Focus. On the smaller two-way speakers, the bass presentation was equal. The midrange and treble seemed more present with Rogue. But it did not sound edgy or harsh at all. (Maybe my 10-year old, heavily used Bryston is starting to show its age).
  Versus my all Class A Pass Labs XA30.5, the Rogue had a significantly leaner presentation, but I mean that in a good way. The Rogue’s bass again was so damn tight that it makes you think that other amps have a tone control turned up somewhere — especially with the generation two Focus speakers I use.
  Compared to the my reference Pass X350.5, priced at $13,000, the Medusa was similar in bass presentation, with maybe an edge in tightness when listening to the Legacy Focus. The Rogue was slightly more present in the treble, and the Pass supersymmetry MOSFET design seems to have a slightly less analytical presentation than the Medusa. The Pass’ stereo image is a bit larger and diffuse, while the Medusa’s image is precise and measured.


  The Medusa’s ability to deliver deep, precise bass and clean, smooth (but accurate) mids and treble was showcased through all my speaker setups. The ribbon-tweeter based Legacy Studio never sounded better on the top-end. The Westlake LC2.65 and Paradigm 8s also were perfect mates for this amplifier, The Paradigm Signature S8’s beryllium tweeter transients are excellent with good amps, and the Medusa manages to transfer its midrange and treble presence through the Paradigms — without sounding exaggerated. 
  One extra point of emphasis: vinyl-obsessed audiophiles will want to try this amp. The Medusa’s bass speed makes LP listening a more satisfying experience. Depending on cartridge used and that pesky RIAA curve, records can sound a bit thick (warmed, if you will) in the mid bass that gets re-thickened through preamps and low slew-rate analog amps; the Rogue does not impart any extra emphasis or sluggishness in the bass. Almost all the LPs I played via the Marantz TT-15 turntable, Pass XP-10 line preamp, XP-15 phono preamp and Rogue Medusa amp seemed more detailed and with less bass bloom.
  I had no problems with the Medusa — except when I stripped out a screw when putting the cover back on after my photo session with the amp’s internals). This build quality is typical of Rogue Audio ‘s hand-assembled quality. It never missed a beat. It ran warm, but never hot, and was quiet as a digital church mouse.
  In thinking about this amp as I wrote the review, the inevitability of digital amplifiers in the audiophile world came into clearer focus. The hybrid amps, and new generation of all-digital designs are going to become more plentiful; there is no stopping it. You already see digital amp technology used extensively on the professional side where smaller and energy efficient amps are made necessary because they are attached to speakers. And with digital amps like Rogue, the newer Bel Cantos and Pioneer’s new Elite class receivers entering the consumer fray, the market is destined for growth. If they sound as good as the Medusa, I am all for it. Definitely going to get a Medusa for my reference system.

The verdict
  The hybrid tube/Class D digital Rogue Audio Medusa is one of the best amplifiers I have auditioned. It renders a very accurate soundstage with tight bass and a very layered top end that matches or exceeds much more expensive analog amps. It can drive most any speaker, and simply gets out of the way when playing the more revealing, high-resolution music. Combine the sound with less produced internal heat, longer component life and a very reasonable price tag for a high-end audiophile component, and the Medusa just might be the ideal, modernaudiophile amp. We are proud to give it a Stellar Sound Award.

The EAN Interview!
Rogue Audio Chief Talks About
New Digital Hybrid Amplifier
Rogue Audio President
Editor’s Note: I have known Mark O'Brien since 1997, shortly after he created his small company, Rogue Audio. In that time, he has created a series of finely crafted, built-in-Pennsylvania tube amplifiers and preamplifiers. Breaking out of that traditional tube amp realm with the addition of the new Medusa hybrid amplifier, I recently conducted a brief Q/A session on his latest creation.
—John Gatski

EAN: As a tube amp designer, What made you want to design a digital amplifier?
MO: Class D amplifiers offer some significant benefits in terms of size, efficiency “green operation” and cost of ownership. Furthermore, the power tube maintenance associated with tube amplifiers can be a deterrent to ownership for some audiophiles. By combining the best of both worlds, I wanted to develop an amplifier that offered the sonic benefits of a large tube amp without any of the downsides. Essentially a compact, cool-running, yet powerful tube amp that an owner can just stick in a cabinet and forget about.EAN: What do you think the sonic benefits are of such a design?
MO: I think both of our new hybrids sound terrific and have excellent resolution as well as tremendous bottom end slam. They also provide tube smoothness without being overly euphonic. I really like the way they sound!
EAN: Can you gives a brief design run down on your design's circuit? Signal path components, etc.
MO: We use an OEM Class D module but bypass virtually everything on it except the modulator and MOSFET output section. All of the input and buffering is our own design and realized on our own circuit board. Generally speaking we use a proprietary input and intermediate stage that forces the output section to take on more of a tubelike sound quality. We also use large linear power supplies and very high quality parts to get lots of headroom and a very clean sound.
EAN: How does it differ from some of the other digital designs currently on the market, ICE, etc,.
MO: During the development phase we built some pure Class D amps as a baseline, and they tended to sound pretty much the same. It took us awhile to get it just right, but when you bring tubes into the mix I believe it really brings the sound to another level.

 ©Articles on this site are the copyright of the Everything Audio Network. Any unauthorized use, via print or Internet, without written permission is prohibited.

Monday, June 18, 2012

Audiophile Amplifier Preview!
Bob Carver LLC Introduces
20-Watt WPC Stereo Tube Amp

Bob Carver's Black Magic 20

by John Gatski
Audio industry veteran Bob Carver has introduced a new stereo tube amplifier, the Black Magic 20, through his company, Bob Carver LLC.
The vintage-looking VTA20S, (think of old Fisher or Macs) is a EL84-based amp, and will be built in Kentucky. Features include point-to-point wiring, auto-bias and low idle current. Carver says his new amp features premium parts and a special power supply, which contributes to its open, sonic signature. The amp's specs show that the VTA20 is surprisingly light at 17 pounds.
The Black Magic 20 joins other Bob Carver LLC products including the Black Beauty 305 and (VTA305M) and Cherry 180 (VTA180M). Click Bob Carver VTA20S for more info.

Tuesday, June 12, 2012

Headphone Review!
Shure SRH1840 Ups HP Ante
With Bass Accuracy, Extended Highs

Price: $699
For: audiophiles, recordists, pros
Likes: bass is right on, accessories
Dislikes: We love this headphone!
More info:
Shure SRH1840

by John Gatski

Shure’s new SRH1840 headphone reveals how committed the venerable microphone company is to producing high-quality accurate headphones. Since it created the SRH line a few years ago, each new flagship model has upped the accuracy.
The latest version of the SRH headphone series, the SRH1840, priced at $699 retail has been designed to such a degree that it seriously challenges high-end headphones that cost considerably more.

The SRH1840 contains 40-mm neodymium drivers that are tuned to get the great accuracy, especially in the bass. The drivers are also contoured for an extended high-end response without too much presence. As Shure’s flagship headphone, premium parts and materials are used on the SRH-1840, including high-grade aircraft aluminum yokes, all-steel driver frames, lightweight headband materials, an oxygen-free copper cable and Kevlar reinforced cable jacket to assure the cable does not break at the maximum stress point. The headphone weighs less than .6 of a pound.
**The SRH1840 comes with a nice vinyl case equipped with 1/8th-inch to /1/4-inch adapter, an extra cable and replacement earpads. The Shure folks sure don’t skimp on their headphones.

Thankfully, Shure has allowed the bass of the SRH1840 to be much more natural in response. It does not have a heavy midbass boost. To me that characteristic is key to its accurate sound.

Spec-wise, frequency response is listed as 10 Hz to 30 kHz with no tolerance listed. Typically, real world bass response of headphone drivers extend to 50 Hz. It’s hard to get true low bass out of a small driver that is not housed in a big box. Thus, in order to give headphones an audible sense of bass, many manufacturers increase the mid to upper bass response (80 to 200 Hz) so that the listener actually hears bass. How much of the midbass bump is added, depends on the manufacturers intended design.
Thankfully, Shure has allowed the bass of the SRH1840 to be much more natural in response. It does not have a heavy midbass boost. To me that characteristic is key to its accurate sound. The midrange is dead on as well — with just a hint of presence boost.
Others specs worth noting include a rated sensitivity of 96 dB SPL/mW @1 khz. Impedance is 65 ohms.

The setup
I reviewed my SRH1840s with several headphone amps including the Benchmark DAC1 PRE, the Benchmark stand-alone H1 headphone amp, a Lavry DA10, the headphone amp section of AVA FET/Valve preamp, as well as a number of handheld recorders and a Trident/ORAM console that I use extensively for home recording.
I compared the Shure SRH1840 to other headphones I had on hand, including AKG K701/702, Sony MDR-7510, Ultrasone HF 2000, as well as the Shure SRH940 closed-back ‘phone. Sources included SACDs and DVD-As via the Oppo BDP-95 player, digital downloads from HD Tracks and numerous high-res 24-bit recordings of my own guitar recordings — jazz guitar and acoustic guitar.
To break in the SRH1840, I plugged into a CD player, popped in a CD, keyed in repeat, and let it play continuously for three days to loosen up the drivers.

The audition
Right off the bat, the Shure’s spacious, wide and deep sound stage impressed me, but the key aural ingredient was the bass accuracy. No midbass humps and boomy thickness that often pervade headphones these days — just a relatively flat low end that does not distract from the music. This kind of clean bass allows you to hear deeper into the music for pleasure listening, or deeper into a mix if you are using them for tracking recordings.
For example, the 1995 Natalie Merchant Tigerlily DVD-A cut, “Beloved Wife,” has a prominent electric bass line that many headphones over hype making the bottom end too muddy. On the Shure ‘phones, the bass is noticeable, like on my reference speakers, but never gets in the way of the song. It sounds like an electric bass instead of a Hip-Hop car stereo war.
Initially, this bass accuracy might make music sound brighter than some listeners expect, but after listening for awhile you really appreciate the clarity of the midrange and the high-end — without the distracting bottom-end mud.

Benchmark DAC1PRE amd SRH1840
I found the Shure SRH 1840s to work well with all kinds of music, including all sorts of vocal arrangements, Classical, Jazz, and Pop. Classical violin was rendered with a smooth, yet present, top end, and I could easily hear the string overtones on 24-bit recordings.
With my assortment of handheld and portable digital recorder/players, the Shure SRH 1840 was an ideal mate. They are not hard to drive. I used the headphones extensively with my TASCAM DR-100 high-resolution, handheld-recorder, and even my gain-challenged Yamaha Pocketrack W24 portable recorder/player could drive the Shure to adequate levels.
Versus the AKG K701 or the K702, the Shure matched up very well. The AKG’s have a wee bit of midbass bump compared to the Shure, but it is not extreme. Both headphones have the ultra-detailed upper end presentation. The AKG may have an edge in smoothness, but it is really close. The AKG is as comfortable, but bigger. The lightweight Shure SRH1840 almost disappears on your ears. It has a fantastic feel on my larger ears and does not press against my glasses.

Since acquiring the SRH1840, it has become my go-to, open-back headphone for use with all my portable high-res players. I also use it extensively with all my home audiophile headphone-enabled equipment, home-recording master recorder and analog consoles.

The Shure SRH1840 is not a low-cost headphone at $699, but neither is it high-end audiophile priced. The SRH1840 is very well made, and Shure should be commended for offering so many included accessories; a classy vinyl case, extra ear pads, the termination adapter and an extra cord just add to the perceived value of the headphone.I had no complaints at all with the SRH1840; it is comfortable, light weight, not difficult to drive and it looks thoroughly modern. Since it is an open-back ‘phone, it does not isolate the sound from external noise, but that is why we have closed-back phones. If you want isolation, try Shure’s SRH940. Its sonic signature is similar on the top-end, but it does have a more pronounced midbass — not excessive, but noticeable.

The verdict
The Shure SRH1840 is a terrific, high-end headphone that is moderately high-end in price at $699, but certainly not way out there. I have auditioned headphones in excess of $1,500 dollars that are not this clean. Since acquiring the SRH1840, it has become my go-to, open-back headphone for use with all my portable high-res players. I also use it extensively with my audiophile headphone-equipped gear, home-recording master recorder and analog consoles. Its accurate bass delivery, detailed midrange and treble make this headphone a no-brainer. Ditto for the Stellar Sound Award.

©Articles on this site are the copyright of the Everything Audio Network. Any unauthorized use, via print or Internet, without written permission is prohibited.