Rogers High Fidelity KWM-88 Corona Integrated Amplifier

High-Tech Meets Tubes

Equipment report
Categories:
Integrated amplifiers
Rogers High Fidelity KWM-88 Corona Integrated Amplifier

You probably wouldn’t use a $15,000 amplifier to drive a $1500 speaker, but I did. In order to see how the Corona drove a different speaker, I connected my KEF Q700 speakers. This three-way cost $1500/pair when last produced, but represents an alternate load for the amp. I’m glad I tried it, as the KEFs have never sounded so good. I was particularly amazed at their bass performance. In the Ultralinear setting with the KT150 tubes, on Folia: Rodrigo Martinez 1490, bass extended quite deeply, with good pitch definition and surprising impact. I haven’t heard such bass from the KEFs before. Surprisingly, their treble performance was equally good; the opening cascabel whacks were extended and harmonically accurate, with just the right amount of impact.

“Miserere” had an agreeable soundstage, possibly a bit left-skewed. There was a slight high-frequency distortion (it’s a characteristic of the recording). The sound of the distant solo group was a lifelike blend of echo and direct sound, which produced realistic separation of the groups.

The “Snilla Patea’” fiddle was spot on, with a full, rich harmonic spread sounding whole and accurate. Choral dynamics were agile, ready to change levels at the drop of a hat.

Comparison
My Audio Research LS28 linestage and VT80SE are somewhat similar to the Corona in that the VT80SE has a similar automatic bias circuit that allows it to use different output tubes. I’ve tried KT88s in addition to the stock KT150s. It’s only rated at 75Wpc, however, with tube life anticipated at 3000 hours. The 6H30 tube is used as the driver tube. A meter in the rear of the amplifier tells you how much time is on the output tubes. The LS28 linestage uses only 6H30 tubes in a hybrid circuit. Unlike the Rogers amp, the LS28 has many controls, including a channel-balance adjustment, phase-reversal switch, and even a display of hours used on the tubes (a 4000 hour lifespan anticipated). Prices for the VT80SE and LS28 are $9500 and $8500, respectively. Of course, an interconnect is required to connect the two components, and that can be as expensive as you like. I use Van den Hul’s balanced The Mountain interconnects in my system, priced at $1454 for a meter length. So that makes $19,454 for the Audio Research/Van den Hul system, a bit more than the Corona. The Audio Research requires two shelves, and is larger than the Corona amp. So there’s a space cost as well as a monetary one. 

The Audio Research LS28 has a normal metal remote which operates smoothly and quickly. All the controls on the linestage are on the remote. Tubes were KT150s, the stock tubes offered with the VT80SE. The amp has no remote.

On Folia: Rodrigo Martinez 1490, cascabels were located in the expected position in the soundstage, a bit to the right of where they appeared with the Corona. Bass was deep and pitch accurate, but less punchy than with the Corona. The viola da gamba tone appeared spot on. Dynamics were forceful, but the Corona’s were even more so.

On “Miserere,” the solo tenor had a bit of the left skewing the Corona had exhibited, but the soundstage was more evenly spread between the speakers. The distant solo group sounded more deeply immersed in reverberant mush, obscuring some of the words. The Corona caught the echo and words pretty close to ideally. Finally, there was some overlaid shatter distortion, which I hadn’t noticed before.

Finally, “Snilla Patea” sounded as realistic as I’ve heard it. The fiddle harmonics were perfect, the chorus sounded like very well-trained vocalists singing together, capable of startling dynamic shifts. Wow!

So does the Corona represent a good value for its high price? Unfortunately, I had no similarly-priced integrated amp for comparison, but the Corona was quite close in performance to the slightly more expensive Audio Research amp and preamp, which are highly regarded, so I think its value must be excellent. And it has some technical features, like the very useful remote control, that surpass the Audio Research duo.

Bottom Line
Let’s review the positive and negative factors for the Rogers KWM-88 Corona integrated amplifier. Appearance—outstanding. The red chassis adds a touch of class. Technology—very advanced. Uses cell phone or tablet app for remote, and an automatic bias circuit to manage tube settings. Sound—very high quality. Best bass I’ve heard from a tube amplifier, fantastic dynamics, very good harmonic accuracy. Size and weight—heavy but manageable. (Sooner or later this will be important to you.) Ease of operation—extremely easy to operate. Controls are a piece of cake; the remote app running on a cell phone makes remote operation easier than ever and informative. Someday all remotes will work this way, but the Corona had it first. Build-quality—dreadnought construction. Warranty—best in the industry. In sum, the Corona is expensive but worth it.

Specs & Pricing

Power output: Ultralinear 100W RMS, triode 80W RMS
Tube complement: 2x 6SJ7, 2x 6SN7, 4x KT88 or KT150
Frequency response: ±0.1dB from 20Hz to 20kHz
Gain: 35dB
Input/output impedances: Four unbalanced, 100k ohms/2 ohms to 32 ohms
Weight: 60 lbs.
Dimensions: 17" x 14" x 11.5" 
Price: $15,000

ROGERS HIGH FIDELITY
10 Holden Street
North Adams, MA 01247
(845) 987-7744
rogershighfidelity.com 

Associated Equipment
Speakers: Affirm Audio Lumination speakers
Amplifiers: Audio Research VT80SE stereo amplifier
Preamplifier: Audio Research LS28 linestage Digital sources”Dell Latitude E6330 laptop computer running 64-bit Windows 10 Professional and Roon music server software version 1.6; PS Audio DirectStream DAC
Interconnects: Van den Hul The Mountain balanced interconnects, High Fidelity Cables CT-1 Ultimate interconnects
Speaker cables: Van den Hul The Cloud speaker cables
Power cords: Purist Audio Design Venustas power cords, Blue Marble Audio Blue Lightning power cords, Clarity Cables Vortex power cords, Audience powerChord e, Au24 SE LP powerChord power cord
Digital cables: Paul Pang TZ YUN Red II USB Cable, Audience Au24 SE USB cable
Power conditioners: Shunyata Denali, Audience aR6-T