Integrated Amp Reviews

When I put together my first hi-fi system in the late 1960s, the amplifier was a Kenwood integrated. Soon I replaced the Kenwood with a Sony integrated, and then, a few years later, I bought a Lecson preamplifier and power amplifier pairing. It's been separates for me ever since.

However, a reader wrote this comment on Stereophile's website a while back: "It will be interesting to see if Stereophile catches up to the focus on active, integrated designs. The relevance of separates seems to be waning in comparison to these sexy and modern designs." The commenter was referring to fully integrated, active loudspeakers, but his point could equally refer to the increasingly common integrated amplifier that incorporates line and phono analog inputs plus a versatile, network-connected D/A section.

In January 2020, I reviewed such a streaming integrated amplifier, NAD's Masters Series M10, which I purchased after the review was published. The M10's Dirac Live low-frequency room equalization made it a natural partner for my long-term reference standmounts, the KEF LS50s, which I had also purchased following a review.

So when Editor Jim Austin emailed me to see if I would be interested in reviewing a new streaming integrated amplifier, the Attessa from British manufacturer Roksan, which, like the M10, can be controlled with the BluOS app and is priced at an affordable $3399, he didn't have to ask twice.

The Attessa...
... is housed in a slim, rack-width steel chassis with an anodized aluminum front panel. A large control knob dominates that panel visually. Rotating it controls the volume; pressing it mutes the outputs; pressing and turning it switches between inputs. This knob is said to give haptic feedback, ie, to vibrate when you use it, but I found this very subtle.

To the right of the knob is a horizontal, orange, thermometer-style, OLED volume display with a 3.5mm stereo headphone jack at the far end. To the knob's left is an array of input-indicator icons, each of which lights up orange when selected.

The back panel has, on its far left, two pairs of loudspeaker binding posts; next come three pairs of RCA jacks, for a moving magnet phono input, and two line-level analog inputs, one labeled "Variable Input (No signal sense)," the other "Fixed Input with signal sense." Next to those is a fourth pair of RCA jacks, labeled "PRE OUT/SUB." Also found back there are several digital connections—two each coaxial and optical S/PDIF, an Ethernet port, two USB Type A ports—one is used for a Wi-Fi receiver—and a USB 3.0 port labeled "BLUOS SERVICE ONLY." The Attessa also accepts Bluetooth audio data encoded with the SBC, aptX, and AAC codecs.

The Ethernet and Wi-Fi ports accept audio data sourced via the BluOS app. As well as playing back audio files from local storage, BluOS serves up a plethora of streaming services including Qobuz, Tidal, Amazon Music, Spotify Connect, Deezer, and TuneIn Radio. The Attessa's volume can be adjusted and its inputs chosen with the BluOS app or with the provided slim plastic remote control.

The chassis interior is dominated by a massive, 400VA-rated, toroidal power transformer on its left and by the amplifier's printed circuit board, with its heatsinks, on the right. The power amplifier's output stages each use two pairs of complementary devices, these biased into class-AB. Between the transformer and the back panel are two stacked printed circuit boards carrying the digital S/PDIF input, Ethernet, USB, and BluOS receiver circuitry and the D/A processor. D/A conversion is handled by a Texas Instruments/Burr-Brown PCM5242 DAC chip, a two-channel sigma-delta part that's capable of handling sample rates up to 384kHz with bit depths up to 32, though the datasheet on the TI website quotes a S/N ratio of 114dB, which is equivalent to a resolution of 19 bits.

Setup
After installing the Attessa in my system and powering it up, I followed the setup instructions in the excellent manual. The first line of business was to install the MaestroUnite app on my iPhone. This connected with the Attessa and before I could continue with the setup, the amplifier updated its firmware. Once that was done, the app allowed me to choose the sensitivities for each of the Attessa's inputs and the headphone output and to customize the input icons. I stuck with the factory settings.

Although Roksan intends the Attessa to be a Roon Ready device, when I opened Roon 1.8's Settings/Audio page on my Mac mini, I got the message "There's a problem with this device. The manufacturer has not yet completed certification for this device." The rep from Roksan's North American distributor confirmed that they were waiting for full Roon Certification but reassured me that this will be updatable via firmware. I could still stream audio data to the Attessa from Roon using Apple's AirPlay, but as AirPlay is limited to 16/44.1k data, I used the BluOS app instead.

When I ran BluOS for the first time on my iPad mini, it allowed me to name the Attessa, log into my Qobuz and Tidal accounts, and locate my favorite radio stations with the TuneIn function. When I selected "Library" from the list of inputs, BluOS found my network-attached storage and spent a while indexing the files. Once that was done, I was able to use BluOS to select albums, artists, composers, genres, songs, and favorites, as well as folders on local storage. The only idiosyncrasy was that with some locally stored albums, it played the tracks in alphabetical order.

To audition the Roksan's physical inputs, I connected my Ayre C-5xe^MP disc player's single-ended outputs to the Attessa's variable line inputs and its coaxial digital output to one of the S/PDIF inputs. I regret, because of how well it measured—see the "Measurements" sidebar—that I have neither a moving magnet phono cartridge nor a step-up transformer to use with my Linn Arkiv B moving coil cartridge, so I wasn't able to audition the Attessa's MM phono input.

Listening
I started my auditioning of the Attessa with it driving the Mission 770 speakers I reviewed in the November 2022 issue, which I had been powering with the Parasound Halo JC 1+ monoblocks. The news had just come in that pianist Lars Vogt had passed away, aged just 51. I used BluOS to cue up his performance of Brahms's Second Piano Concerto with the Royal Northern Sinfonia (24/48 FLAC, Ondine/Qobuz), a favorite recording.