September 2017

Rogue Audio RH-5 Headphone Amplifier And Stereo Preamplifier
A venerable two-channel company's maiden voyage into headphone audio.
Review By Dave Hanson

  The headphone amplification category has grown exponentially in recent years, and with it, several brands have risen from start-ups to household names for personal audio enthusiasts: Schiit, Woo, Cavalli, Questyle, Bottlehead and Eddie Current, just to name a few. One name that has likely evaded many of those enthusiasts, however, is Rogue Audio. For over 20 years, Mark O'Brien and Phil Koch have been making quite a name for Rogue in the world of two-channel audio amplification, where their products are very well regarded. After beginning to dabble a bit in some truly high-end headphones such as the Abyss Headphones AB-1266 ($5495), O'Brien decided to dip his toes into the headphone amplification waters.

"I wanted a really good headphone amp for myself and I loved the challenge of creating it," O'Brien says.  "I wanted it to be powerful, quiet, balanced, and completely flexible in terms of headphone connectivity. I also wanted it to be reasonably affordable." To achieve these goals, Mark felt a tube hybrid design would make the most sense, and employed a mu follower circuit – a topology Rogue often uses in their preamplifiers. The result is the Rogue Audio RH-5 Headphone Amplifier and stereo preamp ($2495).

Welcome To First Class
A mu follower circuit is designed to deliver a low noise floor, low distortion and excellent audio performance. Providing some insight into the design, O'Brien says, "This design uses one half of a dual triode (the 12AU7) arranged to act as a constant current source for the other half. This forces the tube to act as a pure voltage amplifier, which works very well in this application." And because the circuit is also well-suited for the needs of a preamplifier, the RH-5 gives owners a nice two-for-one: an amplifier that can sit at the heart of their personal audio and two-channel systems. For the purposes of this review, I'll be focusing on its performance as a headphone amplifier.

That being said, the RH-5 has no shortage of input and output options for either application. The standard model comes with three analog RCA inputs, one set of balanced inputs, one set of RCA stereo outputs, one set of balanced stereo outputs, a balanced 4-pin headphone output, and balanced dual 3-pin headphone outputs that also double as two 6.3mm unbalanced outputs. If that wasn't enough already, there is also an option to add a phono board (add $400) that is MM/MC switchable and has 8 loading options. Sheesh! All of the outputs are solid-state buffered, allowing the RH-5 to generate the current required for even the most difficult headphone loads while still doing all of the signal amplification in the tube domain.

The RH-5 is well constructed, with a classy modern look and a very nice digital display on the front panel. The buttons and stepped attenuator have a nice tactile click to them as they are pressed or rotated. All the connectors, buttons and dials are clearly higher quality than stock grade, and the overall fit and finish of the RH-5 is quite high-end.

The amp features protective start-up and shutdown delays, and pressing in on the volume button will turn off the digital display while the amplifier is still running, which is nice in low-light situations. My only complaint here was that it was a little too easy to turn off the display when turning the volume dial, and I did it by accident more than a few times. Still, this was only a minor inconvenience, and audio continued, uninterrupted.

Overall, it's an impressive and polished package. But at the end of the day, the level of refinement in all of these features and aesthetics pales in comparison to the importance of sonic performance. So how did the RH-5 fare? Let's find out.

A Gentleman's Spacecraft
Much like the build, the RH-5's sonic presentation is incredibly refined. This is a gentleman's amplifier through-and-through: there's no extra bloat or slam in the bass, no extra dryness or thickness in the mids, and no extra brightness in the treble. It's an A student, a sonic Eagle Scout that always raises its hand and minds its manners. If it strays from perfect neutrality in any area, it's to deliver a treble presentation with just a little extra bit of extra forgiveness, just to ensure it offends no one. If that sounds boring, let me assure you that it is not, because just as the RH-5 takes care not to offend, it also takes care not to bore listeners with flatness, dryness or lifelessness. It really just provides a very solid technical platform for your headphones to perform upon.

But there is one area where the RH-5 really leaps out, and differentiates itself. And that is in the absolutely massive soundscape it offers. Of all the amps I've heard, the RH-5 is probably easily in the top five in terms of the expansiveness of the stage. It is especially impressive in terms of width, projecting a massive concert-hall-like expanse for the sonic images to live in. Height, width and depth imaging are impressively clean, especially when paired with a good source like the Chord Hugo 2 ($2195).

The sonic images are especially tall when listening to the RH-5, and everything felt that much more epic and grandiose when I was evaluating it. The depth extension and depth layering were also quite excellent, although this was the one area of soundscape performance where I felt the RH-5 ceded a few points to some truly excellent all-tube designs. Even still, I had more than a few of those moments where I had to take the headphones off because I thought the sound was coming from inside the room.

It should really come as no surprise at this point that this is an absolute dream amp to pair with the HD800, especially with classical music. RH-5 gives instruments plenty of separation to pick out tiny nuances and details that are easily missed on other amps. This stands out as especially noticeable with highly revealing sources, allowing the listener to really home in on any instrument they want, and hear it in vivid detail.

The background is reasonably black, which helps the positioning of the images stay in clear focus. I did notice a slight high-pitched hum when there was no music playing however. I'm not sure if this was the amp, or if the tubes might have had some slight microphonics, but once the music started, I didn't hear it anymore on full size headphones. With IEMs, it was much more noticeable along with some lower pitched hum that was inaudible on full-sized cans (neither of which went away once the music started), so I definitely wouldn't recommend it for in-ears.

Still, the background is more than dark enough to make it plainly obvious that the attack and decay of the RH-5 is quite clean. If I had to find a flaw here, I would say that I didn't find the note delivery to be as violently incisive as my reference Wells Milo ($1699). Instead, the Rogue stays true to its gentlemanly approach, delivering dynamic musical texture that is neither flat nor aggressive, but completely by the book. It's hard to complain about an amp that takes this approach, but still, I wish it would have dug-in a little bit harder at times and given me a touch more pop. I feel this would have just added a pinch more emotional engagement and funk factor that would have been nice at times, especially with rock genres. With classical, I think the RH-5's approach is probably just right.

If I were going to compare the RH-5 to a couple of other amps, I would say it sounds a little like the lovechild of the Audio-GD Master-9 ($1430) and the Questyle CMA800R monoblock amplifiers ($3998 per pair). All three are quite neutral in tonality and presentation, with just a slightly warmed top end to prevent unnecessary harshness. Similar to these amps, it possesses a lot of "uprightness" and "cleanliness" in its technique, but it is a bit more fun to listen to than the Master 9. It also possesses a lot of the vast open expanse of the Questyle dual monos, but maybe just a hair less emotional gravitas. Slotted safely in the middle at $2495, the RH-5 is an attractive option for those chasing that clean, upright sound.

Finding The Right Destination
Overall, this is a very good sounding amplifier, with a squeaky clean "reference" type of sound. So who is it right for? I actually used it for a little bit of audio production while I had it on hand, and I found it suited the task perfectly. If you are looking for a reference amp for pro audio applications, I actually think this would be an outstanding choice, especially paired with the Sennheiser HD600 or HD800 and a good balanced cable. I also think this is a great option to satisfy those who want to hear their music on a massive stage, especially classical fans. Every time I popped on a big orchestral piece, I was quickly reminded of just how epic the RH-5's presentation can be. For those who love listening to classical music on the HD800, I would say this is an amplifier you should most definitely check out.

The Rogue Audio RH-5 also pairs quite nicely with the Abyss Headphones AB-1266, providing a clean, clear canvas for the Abyss to pound out its dynamic thunder on. It has plenty of power, and at $2495, it's one of the more affordable options for driving the notoriously difficult Abyss to its full potential.

And finally, in terms of all-around value as a headphone amp, the RH-5 strikes me as being very appropriately priced at $2495. It's not a steal, but it's not overpriced, by any means. It performs at the precise level I would expect for $2495. But, if you are able to use it as a preamp for your two-channel system, I think there is certainly a good opportunity to extract a whole heck of a lot more value out of it. And for those who are able to do that, I would also say this is a piece of gear that is definitely worth an audition.

Additional Equipment Used During This Review
Sennheiser HD800
Sennheiser HD600
Abyss Headphones AB-1266
ZMF Atticus
HiFiMAN HE400
HiFiMAN HE500
Campfire Vega IEM
Wells Audio Milo Headphone Amplifier
Glenn OTL Tube Amplifier
Chord Hugo 2
Audio-GD DAC-19
DanaCable Lazuli Headphone Cables
DanaCable Onyx Interconnects
DanaCable Trustream USB Cable
Wireworld Electra 7 Power Cables
PS Audio Duet Power Conditioner
FiiO X5 Gen III DAP
Tidal Hi-Fi Streaming
Audirvana

Specifications
Type: Solid-state stereo headphone amplifier and preamplifier
Tube Compliment: Two 12AU7/ECC82 tubes
Frequency response: 5Hz to 50kHz (+/-1dB)
THD: <0.05% 
Gain Line Stage: 3dB/12/dB/16dB (selectable)
Rated Output: 3.5W @ 32 Ohms
Output Impedance: <0.1 Ohm (1kHz)
Phono Stage Gain: 43dB and 58dB
RIAA Accuracy: +/- 0.1dB
Phono Overload: 40mV
Dimensions: 15" x 13.5" x 4" (WxDxH)
Weight: 19 lbs. 
Price: $2495 standard, or $2895 with phono stage

Company Information
Rogue Audio, Inc.
3 Marian Lane
Brodheadsville, PA 18322

Voice: (570) 992-9901
Website: www.RogueAudio.com