December 2017

World Premiere Review!
Rogue Audio RP-7 Vacuum Tube Stereo Preamplifier Review
A very flexible and fantastic high-end vacuum tube preamplifier.
Review By Tom Lyle

  It was about a decade ago when I last reviewed a component manufactured by Rogue Audio. I distinctly remember my time spent with that preamp because I was very impressed with its sound quality. But when I un-boxed their new RP-7 preamplifier it looked as if it was made by a different company.  As good as their older component looked, the Rogue Audio RP-7 seemed as if its fit and finish was light years better than the older unit. Of course I'm exaggerating a bit, as I don't remember the older unit looking so bad. Plus I didn't have the older preamp in front of me to compare the two, and I certainly don't remember the older component looking bad, but I was very impressed with how modern and stylish this new rectangular black box looked.

After I connected it to my system and switched its power on, I was even more impressed with the preamplifier's appearance when it's blue LED display lit up. But when I began my listening sessions, I wouldn't have cared if the RP-7 was the ugliest component on the high-end market. This is a modern tube preamplifier that checks every sonic box on a checklist of what one should require, not only a tube preamplifier, but any preamplifier. And as a bonus it looks damn good while performing the task.

Rogue Audio's RP-7 is a stereo tube preamplifier with three pair of gold-plated unbalanced RCA inputs, two pairs of balanced XLR inputs and a pair of both RCA and XLR outputs. Its front panel sports a row of buttons for direct access to each of its inputs, a mono switch, defeatable display, and its processor loop for those using the preamp in a home theater set up. There's a large control knob for balance, and an even larger OLED (organic light emitting diode) display.

The RP-7 has slow start circuitry, and a host of internal features including four 12AU7 vacuum tubes, and a "massive" power supply. Not to be outdone, the RP-7 has a tube-based headphone amplifier with its headphone jack on the front panel.  Its full function remote has a mute switch and controls all that is on the preamp's front panel. The RP-7 is built with some solid-state circuitry inside the chassis, so this officially makes it a hybrid design, but all of the amplification is done in the tube domain. It is a very interesting circuit that takes advantage of the strengths of both technologies. This is a sweet-looking 30-pound preamplifier, plus its sound quality is sure to make buyer's-regret inconceivable.

With all of the information given above I could have ended the review of the Rogue Audio RP-7 right now. And now that I've lived with this preamplifier in my system for a while, I'll save you some time by writing the conclusion of this review now, and fill in the details later: I'm convinced that if one is looking for a mid-priced ($4995) tube preamplifier, this is the one I'd recommend. But there are some that would like it if I describe what it was to live with this Rogue Audio preamplifier. I'm happy to oblige.  I'll start by letting you know what system the Rogue Audio RP-7 was tested in, and that this system was and is quite revealing, and in turn revealed the sonic character of the RP-7.

Auditioned
The system in which I auditioned the Rogue Audio RP-7 has changed a bit since my last review. Until recently the analog-front end of the system trounced the digital-front end. That's not entirely true anymore. This is because I've recently installed into my system AURALiC's latest DAC, the VEGA G2, which replaced the non-G2 version of the AURALiC VEGA. I'm not sure why they decided to keep the VEGA name, since the newer version, along with a major cosmetic upgrade, is sonically far superior than the older model. A review is forthcoming.  I'm very proud of the analog front-end of my system. It brings me hours of musical joy. For a while I've been using the marvelous Italian phono cartridge built by Gold Note called the Tuscany, mounted on a Tri-Planar 6 tonearm, one of the last built by original Tri-Planar owner and manufacturer Herb Papier. The turntable is a Basis Debut V.

When I acquired it, it was a Debut Gold, but then Basis upgraded the turntable to a Debut V, which meant that its plinth had to be re-machined to accept a new AC synchronous motor that replaced the old DC motor. Now that it has an AC motor it means I am able to use the turntable with an outboard power supply. which enables me to change the turntable's speed simply by changing the frequency of the power supply to either 60Hz for a 33 rpm record, or an 81Hz signal for a 45rpm record. Plus, the power supply I use regenerates the AC signal as a perfect sine wave.

The power amplifier in the system remains the Pass Laboratories X350.5, which provides 350 Watts per channel to the Sound Lab Majestic 545 full-range electrostatic speakers. Their lowest bass is augmented by a pair of Velodyne 2500W 15" sub-woofers. At the same time that I'm reviewing the Rogue Audio RP-7's I'm also auditioning the best system-wide power conditioner I've ever encountered, the StromTank S2500. This 135-pound brute uses lithium-ion batteries to completely remove one's system from the AC power that comes into the home. The improvements in sound quality are therefore monumental, since now the system is removed from the power grid. I'm able to connect every AC power cord in my system the StromTank, which sits beside my Arcici Suspense equipment rack, where the Rogue Audio RP-7 rests on its fourth shelf.

Rogue Audio's RP-7 was a pleasure to use. The only complaint I have is that there is no mute switch on its front panel, it is only available on the remote. This was a minor inconvenience only because I listen to so many records. I had to remember to mute the preamp from the listening seat, because if I forget to bring the remote with me across the room to where the turntable is located I either had to lift the tonearm with the volume raised, or go back across the room to retrieve the remove to mute the preamp. Yes, this is definitely a first-world problem.

And so, I had to train myself to mute the preamp from my listening seat – a skill that I learned rather quickly, otherwise, the cartridge would thump, thump, thump in the run-out groove of the record while I would fetch the remote. While I'm at it, I might as well say that for the price of admission, I was expecting the Rogue Audio RP-7's remote to have a metal case rather than the bush-league plastic one that is provided. Again, this is only a minor complaint, but I thought that I should mention it. Other than that, the use of the RP-7 proceeded without any problems whatsoever.

Criticized
Because of many technological advanced, tube components can no longer be criticized using the same language as reviewers and owners of tube equipment once did. This has been a fact for quite some time now. High-end component designers that cannot build a tube component that has a quiet background, extended highs, and a deep, and a pitch stable bass, among other high-end attributes might be better off finding a new line of work. That's not to say that the best solid-state and tube preamplifiers end up sounding the same. Many, including me, find it odd that when considering transparency and lifelike reproduction of music that there can be differences in the sound between a tube and a solid-state component, yet both of them can be considered true to life sounding – or at least as true to life as can be possible with the technology at hand. And this is certainly true of the Rogue Audio RP-7.

For all its positive characteristics, its most impressive is the lifelike reproduction of the instruments and voices it reproduces. And if the recording isn't up to it, or is not reproducing real instruments and voices recorded in a real space, it seems to me as it is awfully close to reproducing exactly what is on the recording without adding any sounds of its own or committing any sins of omission. Yet its sound is different than what I hear from the the best solid-state reproduction in the same price class, or if not in its price class, equivalent level of engineering craftsmanship. The realistic reproduction of instruments and voices, and its ability to be true to the source is due to many factors.

The RP-7's pitch black background has lots to do with this, because if the background is not extremely quiet, this can lead to a decrease in both micro- and macrodynamics, not to mention a preamp's overall transparency. The frequency extremes of the RP-7 were also exemplary – the bass was pitch stable, went as low as the recording demanded and my system reproduces, the treble, as one would hope for from a modern tube preamp, went as high as the recording demanded and my system would reproduce, along with a natural sweetness that tubes are known for and music is meant to sound like (an instrument played "in real life" may hurt one's ears due to its loudness, but its treble shouldn't be "annoying").

Rogue Audio's RP-7 also had a trait that is present in many well-designed tube amplifier, and that is its ability to establish a dynamic distance between the instruments, sounds, and voices it reproduces. Not only could the RP-7 separate instruments and groups of instruments and voices in its huge soundstage, but it did this when two or more instruments were at the same volume, and in the same area of the soundstage. In other words, I could hear the air of the recording venue between the instruments and voices. This occurred even when the sounds reproduced by the PR-7 were not real instruments and voices recorded in a real space, and instead of that air or ambience will be dead silence. Which is pretty cool if you ask me.

With that in mind, when playing either the LP or CD of Jimi Hendrix's Electric Ladyland album, it begins with a sonic blast that is the introduction to "And The Gods Made Love", where drummer Mitch Mitchell strikes a drum, I assume a floor tom, that has bass frequencies dialed in so deep, it is the epitome of the cliché "it rattled the window frames of the listening room". No, this is definitely not a "lifelike" reproduction of a floor tom, but rather the engineering skills of one Eddie Kramer, who might as well have been credited as a member of The Jimi Hendrix Experience on this album. Throughout the album the Rogue Audio RP-7 demonstrated that it had no problem reproducing both the real and the unreal as close as I've heard to what I can only imagine was the original intent of both Hendrix and his studio engineer when painting their psychedelic petroglyph carved into magnetic tape.

When the voices and instruments are "real", as in most of what's laid down during Jimi's cover of Earl King's "Come On", the 60-cycle buzz from his guitar amplifier bleeding into the vocal microphone was loud enough to be annoying, but his voice still sounded real enough to easily imagine him in the room singing the vocal track in the same room as his guitar amp. The genius of "Gypsy Eyes", Hendrix's octave jumping stoner guitar riff combined with Kramer's manipulation of the recording tape to produce a flanging effect, which he did by mixing two identical signals, delaying one by slowing down one of the tape deck's reels by laying his hand on the flange of the reel (thus the name of the sound attained). This creates what's called the "comb filter effect".

Technically, this is explained as peaks and notches within the frequency spectrum related to each other in a linear harmonic series. Varying the speed of the second tape, and thus the time delay, causes them to sweep up and down in frequency. It's easily explained as a swooshing sound, and even easier explained as just freakin' cool. It messes with reality, that's for sure, and is the point of the entire exercise.

Combining this sound with panning the instruments and voices and sometimes the entire program from right to left and left to right is meant to be dizzying, and again, cool. Reproducing this in a high-end stereo system that contains the RP-7 makes "Gypsy Eyes" sound even cooler, mostly because this tube preamp is reproducing the sound as it was meant to be heard. And most likely better than Hendrix and Kramer ever heard it through their crappy headphones and primitive studio monitors. The Rogue Audio RP-7 made it so I was able to enjoy this album from beginning to end without ever doubting I was hearing exactly what was on either the LP or CD, and without ever doubting I would hear it much better through any other preamp.

When I first started listening to the Rogue Audio RP-7 it took me some time to become accustomed to its less forward midrange when compared the two top-flight solid-state preamps I had on hand. I've found this is typical for most tubed based components I've had in my system. This gave the RP-7 a more relaxed, less fatiguing sound than the solid-state units. Both the tubed RP-7 and the solid-state preamps have what I would call a very realistic sound, but they were different, and so this brings me back to the conundrum of attempting to decide which one was more realistic than the other. I found this to be an impossible task. Yes, I know what realistic sounds like, as I've spent countless hours in the recording studio, concert halls, clubs, and even homes where live music was being performed.

The Holy Grail of not being able to tell the difference between a recording and a live performance might not become a reality within my lifetime, but with components such as the the Rogue Audio RP-7 it seems as if we're inching closer and closer every minute. There were times when listening to music when, even if just for a second, an instrument would enter the soundstage from its farthest edge and I'd swing my head to the side of the room as if a stranger had entered the room. I love it when that happens. But that is more akin to a parlor trick, so it is helpful to know that for long stretches of time I'd become immersed in the music, not caring whether or not the preamp was able to fool me into feeling the proceedings were live or not, but instead having the sense that I was hearing exactly what the recording artists, engineers, producers, and anyone else who had a hand in making the recording, intended me to hear.

Love
I also listened to (again) the Mercury Living Presence LP of Antal Dorati conducting the London Symphony Orchestra in the orchestral suite from Prokofiev's opera Love For Three Oranges, the Classic Records 200 gram reissue of this 1957 recording. This LP side makes clear all I've been saying about the Rogue Audio RP-7 being true to the source, and much more. No, I wasn't even born yet when this recording was made, neither was I present when Dorati and the engineering and producing team were listening to the playback speakers and making comments about the recording, or present when Classic Records was cutting the master to press the record. Besides, it is physically impossible to replicate the sound of a 100-plus member symphony orchestra playing in an auditorium with a fifty-foot proscenium with the microphones ten feet above the orchestra located in strategic positions. And yet...

What came forth from my two speakers when playing this LP sounded as I was listening to a symphony orchestra playing on all 16 cylinders at London's Kingsway Hall.But in miniature, so to speak. This was a symphony orchestra sonically drawn to scale, much of it thanks to the Rogue Audio RP-7. The Love For The Oranges suite is a great demonstration piece. It uses a relatively large orchestra loaded with percussion instruments, including timpani, bass drum, cymbals, gong, orchestra bells, snare drum, suspended cymbals, tambourine, triangle, and xylophone, plus instruments one wouldn't expect to be included in a typical orchestra such as tenor saxophone, mandolin, and a viola d'amore that it's such a great piece of music, and one of my favorite Prokofiev scores is almost beside the point.

The music has plenty of melody to satisfy the more conservative music listener, but there's also plenty of darker, more foreboding passages, and at least one passage where Prokofiev creates dissonance by layering disparate melodies atop one another. There are typical Prokofiev rhythms along with a physicality that will test both a component's dynamic abilities, and that's where the Rogue RP-7 again would shine.

This preamplifier seems to take the opposite approach to handling dynamics as one would expect from a tube component of yore – its transients are sharp but almost organic sounding, where the cliché "a straight wire with gain" wasn't exactly true, because I could imagine my system's sound being less natural sounding without the RP-7 in the chain. If you're now expecting me to roll-off all the audiophile clichés such as lengthy reverb trails, a midrange with a palpable presence existing on all the instruments, pin-point imagining, spectacular midrange transparency, the deepest bass, the highest treble, superb transient response, and more, OK, the Rogue Audio RP-7 has all of this and more. But when playing the recording of Prokofiev's suite for The Love For Three Oranges, all I could think about was that this preamplifier sounded like music. And that's the highest praise I could bestow upon high-end audio component.

Happy
I'm happy to say that the Rogue Audio RP-7 was good enough for me to use without yearning to switch back to my reference preamps. Of course, I did switch back to these reference preamps for comparisons sake. I put back into the system the Balanced Audio Technology (BAT) VK-33 preamplifier for a while, a vacuum tube preamp that is one I've used on and off in my system for over two years. This preamp sells for two thousand dollars more than the RP-7 in its standard configuration, and although this isn't a shoot-out, I can honestly say that the two preamps are more the same than different, and that is great praise for the Rogue Audio preamp.

I also reinstalled the two solid-state preamps I had on hand.  After becoming accustomed to the different sound that a solid-state preamplifier offers, it was easy to deduce that both these preamps sounded superior to the Rogue preamp. But I was also astounded that the reference units were not necessarily better in every area. This is not a trivial matter, not only because both these preamps are 2017 Blue Note Award winners, but because these preamps much costlier than the Rogue Audio preamp.

The $12,400 Merrill Audio Christine Reference I've been using as my reference for quite a while, ever since I finished my review in May of this year. The other preamplifier, the recently reviewed Mark Levinson No. 523 sells for $15,000. Before the heads of Merrill Audio or Balanced Audio Technology sit down and write me angry emails, I should repeat that the Rogue Audio RP-7 sounded better in certain areas, but was not better overall. There is also the matter of system matching that might also have come into play. But the Rogue Audio RP-7 tube innards were obviously giving this preamp an edge in the way in what I previously termed as its more "organic" sound. Some might say this was due to the way it minutely softened the transient attack of certain instruments and sounds, but still, it did this by not reducing its transparency, at least none that I could detect.

Fantastic
Rogue Audio's RP-7 vacuum tube stereo preamplifier is a fantastic unit! It is also very reasonably priced at a hair less than $5000. The RP-7 is extremely good looking, performed without a hitch from the beginning of the review period until its end, and is a preamplifier I could easily live with, even though lately I've been using much costlier preamplifiers in my system. It is also a very flexible preamplifier by featuring on its front panel and remote a mono switch, balance control, home theater processor loop, a dimmable and defeatable display, three unbalanced RCA inputs, two balanced XLR inputs, a pair of outputs (XLR and RCA), a fixed RCA output which can be used for an external headphone amp or CD burner, etc.,

Its fit and finish can be compared to units costing much, much more than the Rogue Audio RP-7. I realize that five thousand dollars isn't chump change. But the RP-7 is a modern tube preamplifier that I can recommend for those searching for a preamplifier anywhere near its price, and much more than that. That is why I consider the RP-7 not only a great preamp, but a relative bargain. Recommended? Absolutely.

Specifications
Type: Vacuum tube stereo preamplifier
Tube Complement; Four 12AU7 / ECC82 tubes 
Frequency Response: 1Hz to 50kHz
THD: <0.1%
Gain line stage: 14dB (20dB XLR)
Rated Output: 1 Volt
Maximum Output: 30 Volt
Output impedance: <10 Ohms
Dimensions: 18.5" x 4.5" x 4.5" (WxHxD)
Weight: 30 pounds
Shipping weight: 45 pounds
Power requirements: 115/230V – 50/50Hz
Price $4995

Company Information
Rogue Audio, Inc.
P.O. Box 1076
Brodheadsville, PA 18322

E-mail: info@rogueaudio.com 
Website: RogueAudio.com 

Shipping Address:
Rogue Audio, Inc.
545 Jenna Drive
Brodheadsville, PA 18322