Rogers High Fidelity KWM-88 Corona Integrated Amplifier

High-Tech Meets Tubes

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

The signal circuit may use tubes, but the heart of the amplifier, the power supply, is all solid-state. Built around a 30-pound toroidal transformer (that’s half the weight of the entire amplifier), the power supply is rated for 1800W—way overbuilt.! The Corona is burned in for 100 hours to prevent any infant-mortality problems, and get you well on your way to total burn-in. 

Rogers emphasizes that the amplifier is constructed of aircraft-grade aluminum with military-spec wiring and electronic parts. I don’t know if such construction makes the amp sound any better, but it certainly does make it more rugged and stable. It’s got to be a factor in longevity—the warranty is transferrable limited lifetime, which is about as good as you’ll find, and far better than most competitors. It even applies to amplifiers that are re-sold by dealers. With the exception of replacement tubes, it sounds as if you’ll have a hard time spending any money on your Rogers amp, unless you do something goofy to it.

On the rear panel you’ll find four unbalanced inputs, an IEC jack for the power cord, and two Furutech solid-copper output jacks for the speakers. Input impedance is 100k ohms, which should work with any conceivable source. Unfortunately, there are no line-level outputs to drive powered subwoofers or other external amplifiers. There is also a connection for an included Bluetooth antenna, which is how the tablet or phone connects to the Corona. The volume graphic on the app drives a motorized control which operates the front-panel volume attenuator. 

The remote-control app on my iPad was named Rogers High Fidelity Corona at the Apple App Store. All I had to do was download and install it, and it connected immediately via Bluetooth to the Corona. 

The Corona is a very expensive integrated amp designed to provide extremely high-quality sound from a relatively compact unit. The price tag will place it beyond the reach of most readers, but as with any pricey item, the question of value comes into play. In other words, can you attain the same level of performance for the same price or less?

Setup and Use
Normally, when I get a component for review, I first read the owner’s manual, or at least the set-up guide. The Corona’s manual was provided in digital form as a Microsoft Word document on a USB drive. I quickly printed it out and checked out Section 2, Quick Start. It had pretty good step-by-step instructions for installing and setting up the amplifier—except, several items were omitted. For example, there was an antenna in the amplifier box, but no mention of its function (it’s a Bluetooth connection for the remote control). It appeared to screw onto a fitting on the rear panel of the amp, so that’s where I put it. If the manual had contained a photo or drawing of the rear panel, it might have shown me where the antenna should have gone. There was no specific reference to the remote-control app, either. After checking out a few guesses, I asked Rogers and learned that the app is named Rogers High Fidelity Corona. I probably would have guessed that eventually. But why not just put it in the manual? Once installed, the app connected effortlessly (as noted) to the amplifier via Bluetooth. I installed the app on both my iPad and iPhone, and discovered only one device at a time will connect to the Corona. The iPhone screen is necessarily smaller, but still easy to use. I found myself using it most of the time, since I carry my phone with me around the house.

The Corona isn’t a huge amplifier, 17" x 14" x 11½", but its 60-pound weight needs a sturdy shelf or support with plenty of ventilation for the tubes. For me, that meant the top shelf of my equipment rack, and was I ever glad to have help lifting the Corona to eye-level. 

I connected the Corona to my DAC via High Fidelity Cables CT-1 Ultimate unbalanced interconnects and to my speakers with Van den Hul Mountain speaker cables. Rogers furnished an accessory power cord manufactured by Transparent. It’s a molded cord, but needless to say, it uses top-quality parts in its construction, and is way better than most stock power cords. Of course, it’s not stock, selling for $75 for a 10-foot length. I normally use the stock power cord when reviewing a component, knowing that using an aftermarket cord could make noticeable differences, but since this aftermarket cord came from the Corona’s manufacturer, I used it. The power cord was plugged directly into the wall, not into the Shunyata Denali power distribution system where the rest of my system is plugged.

When I swapped out the tubes, removing the KT150 and inserting the KT88s, I waited the normal amount of time, 30 seconds, before switching from standby to play, and the new tubes worked without any fuss. The new tubes showed up in the information window and the app as being in good condition. I wished the amplifier had used the computer to track the time the tubes had been in service, so I could replace them when they were worn out, but maybe that feature will appear on a later model.

I found myself indulging in some Old Geezer nostalgia: I remember when tube gear was noisy. Not so much now, though; the only noise I heard from the Corona was a slight pop when the amp turned off and when switching between Ultralinear and triode mode. (Rogers says that this has been fixed in current production.)