Rogue Audio RP-7 Preamplifier

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Equipment report
Solid-state preamplifiers
Rogue Audio RP-7
Rogue Audio RP-7 Preamplifier

“Don’t I know you? Haven’t we met somewhere before?” My very thoughts when I first laid eyes on the Rogue Audio RP-7 preamplifier. Then I remembered: It was the Rogue Audio RP-5 that I reviewed back in Issue 260. In all fairness to my powers of observation, the new RP-7 is nearly the spitting image of the RP-5. Externally, it’s the same handsome, full-featured linestage tube preamplifier. Dressed in an immaculate brushed silver aluminum enclosure and accented by round balance and volume knobs and an oval display, there’s a hint of retro-style informing its looks—appropriate considering the quartet of tubes glowing discretely within. So then, given the obvious similarities to the RP-5, what exactly is an RP-7?

The RP-7 is basically everything you may have wanted in the RP-5 and much more. And for some, actually a little less. A quick stroll around to the back panel clarifies this. Arrayed neatly across the expanse of real estate is one of the most comprehensive input layouts I’ve seen in a long time. No longer limited to unbalanced RCA inputs and outputs like the RP-5, the RP-7 goes all-in by offering dual pairs of balanced XLR inputs and outputs. They are MOSFET-buffered to provide a low output impedance for driving long cables or difficult amps. And these are in addition to the trio of RCA line-level inputs and the pair of RCA outputs. You can never have enough outputs, and these (unbalanced or balanced) are especially handy should you get the hankering to add a subwoofer or second amplifier. Adding a finishing touch are the fixed output and processor loop (it will bypass the active circuitry) and unity-gain inputs.

With only minor changes, the front panel retains the commonsense layout of the RP-5. Arrayed along the lower portion of the panel are microprocessor-controlled input buttons that include a selector for mono playback. The display has been upgraded to OLED (custom-designed for Rogue) from the fluorescent unit of the RP-5. Large, readable characters provide volume, balance, and source info. The balance indicator button has been replaced by a display-defeat button, indicative of the more serious sonic intent of the RP-7. Another key change is the excellent stepped-attenuator volume control providing 192 steps and 0.5dB increments—a clear advancement over the RP-5’s 60 steps at 1dB per increment. There are no op-amps in its signal path. Carried over from the RP-5 is a “slow-start” on/off sequence with automatic muting when powering up or down. A ¼" headphone output provides the finishing touch to the RP-7’s comprehensive package.

How did Rogue find the interior real estate for balanced operation? Here’s where the “little less” aspect comes in—the RP-5’s phonostage took the hit. This is due to the fact that the RP-7 is based around an entirely different circuit than that of the RP-5, one that’s more complex and space intensive. Permit me, but I think it was a justifiable sacrifice. At this price level, vinyl enthusiasts become real sticklers for their LP playback rigs. They require a wider range of settings, and easier access to those settings as well. Additionally, of all the analog components that benefit most from an “outboard” chassis and the isolation it offers, the phonostage is top of the list. Noise and resonances are much harder to control when a phonostage and its delicate low-level signals reside within the preamp. And as it happens Rogue Audio makes some fine outboard phonostages in its Triton, Ares, and Ares Magnum designs.

Internally, the tube complement comprises four 12AU7/ECC82’s. Rogue employs a mu-follower—a high-gain, low-output-impedance inverting stage known for good power-supply rejection ratio, low noise, and low levels of non-linear distortion. Like the RP-5, the RP-7 incorporates Rogue’s RP-X hardware/software platform, developed in-house in order to bring more functionality to Rogue’s designs. The tube circuitry is computer optimized for accuracy, ultra-quiet operation, and reliability. The headphone amplifier is a tube/solid-state hybrid that’s fed from the outputs of the tube stage. It’s been designed to offer sufficient power to drive higher-impedance headphones.

The ten-button remote control, the same as the RP-5’s, allows you to access volume, balance, source, mute, mono, and on/off functions from your listening position. In my opinion a more upscale version in a brushed silver housing would better complement the RP-7, rather than the econo-black plastic unit that is supplied. One operational nitpick: The mute feature is not accessible from the front panel; you can only mute via the remote control. So keep that RC handy!

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