Integrated Amp Reviews

I was less than thrilled by Editor-in-Chief Jim Austin's suggestion to review the solid-state Krell K-300i integrated amplifier ($7000, plus an additional $1000 for the optional DAC). I had recently reviewed another $7000 integrated amplifier, the quite different hybrid Aesthetix Mimas, and while I ended up liking the Mimas a whole lot, I felt decidedly lukewarm about having to recalibrate expectations for another integrated, especially one that costs far less than my reference Dan D'Agostino Progression monoblocks ($38,000/pair) and whose DAC option is a fraction of the price of my reference dCS Rossini DAC/Rossini Clock combination ($31,498 plus cables). How good could it be?

There's something happening here (footnote 1)
There were also lingering questions about what had happened to Krell after its founders and co-owners, Dan D'Agostino and Rondi D'Agostino, were axed by an investor who, in the words of Krell's present-day COO Walter Schofield, "did not respect the legacy of the brand." Eventually, Schofield reports, the investor "walked away from the company."

Since Dan had already moved on and founded Dan D'Agostino Master Audio Systems, his former wife, Rondi, repurchased Krell in May 2016. After Schofield proposed a new business plan that would address reliability and performance issues, he came onboard as COO. The first all-new product from the re-envisioned and reinvigorated company, the Krell K-300i integrated amplifier, was released in early 2019 as the successor to Krell's US-manufactured Vanguard integrated amplifier.

That I had nothing to worry about (as if it were possible for a Jewish only child not to worry) became clear when I heard the K-300i shortly after its release, during Graham Audio's launch of their LS5/9f loudspeaker at Gig Harbor Audio near Seattle. After spending several hours listening to the speaker with an amplifier that did not do it for me at all, my ears perked up when proprietor Erik Owen switched to a brand-new, hardly-broken-in Krell K-300i. One listen to the difference in midrange (the Krell had a full and warm one, thank God) and top (the Krell's was smooth and extended rather than hard and unwelcoming) made clear that my editor was on to something. A mere two months later, a K-300i made its way to Port Townsend for review.

What it is . . . became increasingly clear
While my sample of the K-300i was breaking in, Dave Goodman, Krell's longtime director of product development, gave me a rundown of its key attributes. Goodman, who was working for Sikorsky Aircraft when he discovered Krell's headquarters by chance while driving through an industrial park, has either designed or served as lead engineer for multiple Krell products over his 32 years with the company. Most recently, he designed the K-300i's optional DAC section and was responsible for the final development and implementation of its trademarked iBias technology (footnote 2).

The K-300i's key features include low-negative-feedback, fully differential circuitry, a 771VA power transformer with 80,000µF of capacitance, and a Cirrus Logic CS3318 volume control that runs balanced to ensure that balanced input signals, including those from the DAC, remain balanced until they reach the amplifier's main gain stage. All circuits up to the driver stage operate in pure class-A. Krell claims that this integrated was designed to output up to 150Wpc into 8 ohms and 300Wpc into 4 ohms, with its iBias technology allowing the amp to deliver up to the first 90W in class-A—"without the excessive heat and power consumption of traditional Class-A designs," Goodman told me by phone. (For his complete discussion of iBias and other unique aspects of the K-300i's design, please see the sidebar.)

The front panel includes power, source selection, navigation, menu, and volume buttons; a USB-A receptacle for playback from USB sticks; and an illuminated display. All of the panel's indicators except for volume level were easy to read from my music room's sweet spot, which is located approximately 12' away from my Wilson Audio Alexia 2 loudspeakers. You can assign custom names to sources, adjust volume offset to compensate for different source output levels, choose between variable and fixed output levels, and use the Fixed option to enable a home theater surround-sound processor to control the volume of the left and right front speakers along with all of the other home theater speakers.

The Krell K-300i's rear panel includes two pairs of balanced analog audio inputs and three pairs of single-ended analog audio inputs. Given that my reference D'Agostino Progression monoblocks only accept balanced inputs, I stuck with balanced interconnects throughout the review period. Because the K-300i's sole pair of preamp outputs is single- ended, and I didn't want to use single-ended–to-balanced adapters (which might have compromised sound quality),

I was unable to pair it with the Progressions to test it as a stand-alone preamp.

The Krell's loudspeaker outputs come with EU-approved plastic safety fittings, a challenge for bifocal wearers. But once you get the hang of things, it's easy to connect and tighten spade lugs.

A number of the K-300i's rear-panel inputs and outputs are activated with the optional digital module, which uses the ES9028PRO Sabre DAC chip. These include a USB-B input, which accepts signal from external devices such as HDs, NAS drives, and computers; a Bluetooth receiver with aptX; HDMI 2.0a and HDCP2.2 inputs and a single HDMI output; and TosLink optical and S/PDIF coax inputs. An Ethernet input comes standard, as do an RS232 control, baseband RC5 input, and 12VDC trigger input and output.

The DAC, which fully decodes and renders MQA and is a Roon endpoint, decodes PCM up to 24/192 through the rear-panel coax, HDMI, and USB-B inputs; the optical input is limited to 24/96. Higher PCM rates are downsampled. The USB-B input also plays DSD up to 128; DSD256 may be converted to a lower DSD rate, depending on the capabilities of the source device. Both network audio and the front-panel USB-A input work in conjunction with a downloadable ConversDigital mConnect Control app for iOS and Android to decode PCM up to 24/192; those inputs only play DSD64 and will not down-convert higher DSD rates. Depending on the capabilities of your network music server software, you can get around DSD limitations by setting it to down-convert higher DSD rates to DSD64 or to PCM. (Roon can do this.) The mConnect Control app also handles network streaming audio from Spotify, Tidal, Deezer, Qobuz, and vTuner internet radio. It won't wash your windows, however.

There's also a very handy remote control that can select inputs, control and mute volume, adjust balance, and access menu functions. Replacing its two AAA batteries is a pain, however, because it involves using a supplied Torx screwdriver to remove and replace four teeny, easily lost T10 screws.

The K-300i's manual cautions against plugging it into a power conditioner. When questioned, Goodman said, "Krell amps have always had very large power supplies that deliver a lot of current. This means that the power conditioner has to be at least as big as the power supply in the amplifier to avoid limiting power and negatively impacting the sound. The K-300i may be one of our smaller amplifiers, but it has an over-750W power supply. To get everything you can out of it, your power conditioner should be rated for at least 1000W." Goodman subsequently acknowledged that conditioners such as AudioQuest's Niagara 5000, which, when run from a 120V supply, can sustain 20 amps for up to 25ms, should be adequate when the K-300i is connected to one of its high-current outlets. Thus, I stuck with my own Niagara 5000, which I use with my reference D'Agostino amplifiers.

Stop: Hey, what's that sound?
My review strategy was pretty straightforward, at least at the start. To evaluate the K-300i solely as an integrated amplifier, I bypassed its DAC section by sending signal from the Rossini DAC's balanced analog outputs to one of the Krell's pairs of balanced analog inputs. After turning the Rossini DAC's volume all the way up, I used the K-300i's front- panel navigation menu to select the correct input. (I could have used the remote control instead, but I kept it on the couch to control volume.) The source was my customary Roon ROCK-equipped NUC, with playback controlled by a Roon app downloaded to my iPad Pro.

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Footnote 1: With thanks to Buffalo Springfield, whose 1967 song "For What It's Worth" figured in one of my many awakenings.

Footnote 2: Former Krell engineer Todd Eichenbaum did the original proof-of-concept work on iBias.