Sidebar 1: Krell Designer Dave Goodman on iBias and Other Features
The K-300i uses modern techniques that we've implemented in the recent designs and upgrades we've issued since the split. First, it has a differential current-mode input stage that drives a fairly conventional output stage. Though we've done such designs before, I discovered that by fine-tuning parts of the gain stage I could significantly reduce distortion—specifically the second-harmonic component. The predominant characteristic is now the third harmonic, which we've found makes the K-300i sound much better.
In…
Sidebar 2: Specifications
Description: Solid-state integrated amplifier with iBias, class-AB output stage, and optional D/A module. Analog inputs: 2 balanced (XLR), 3 single-ended (RCA). Optional digital inputs: 1 Toslink optical; 1 S/PDIF coaxial; 2 HDMI (HDMI 2.0a, HDCP 2.2; supports DSD audio and 4K video); 1 USB-A (USB 2.0 host); 1 USB-B (USB 2.0 audio device); 1 Bluetooth with aptX. Outputs: 1 pair speaker outputs; 1 pair single-ended preamplifier outputs (RCA); 1 HDMI output; 1 12V trigger output. Output power: 150Wpc into 8 ohms (21.8dBW), 300Wpc into 4 ohms (21.8dBW). Voltage…
Sidebar 3: Associated Equipment
Digital sources: dCS Rossini DAC & Rossini Clock;
Mytek Brooklyn DAC+; Apple 2017 MacBook Pro computer with 2.8GHz Intel i7, SSD, 16GB RAM; Intel NUC7i7BNH with 8GB RAM, 128GB SSD running Roon; Linksys routers (2), Small Green Computer Systemoptique optical isolation bundle, TP-Link gigabit ethernet media converters plus multimode duplex fiber optic cable (2); Small Green Computer linear power supplies (4) & Small Green Computer 200W Linear Power Supply; external hard drives, SSD USB sticks, iPad Pro.
Power amplifiers: Dan D'Agostino Master…
Sidebar 4: Measurements
I measured the Krell K-300i using my Audio Precision SYS2722 system (see the January 2008 "As We See It"). I usually precondition amplifiers by running them at one- third power into 8 ohms for an hour. The Krell almost made it, turning itself off after 55 minutes, with the front-panel display showing the message "Over temperature left channel." The top panel over the heatsinks was hot, at 142.8°F (61.6°C), but cooler over the transformer at 113.1°F (45.1°C). This is a tough test for an amplifier with a class-AB output stage, as one-third power results in the…
My in-person introduction to Devialet's products was under auspicious circumstances. I was in Paris for what would be a month-long vacation; my wife was there to give some lectures, but I was free to roam the city, take pictures, practice my bad French, and enjoy the excellent food—the experience of a lifetime except that, a few days in, I was missing music. Still early in my visit, I wandered by the big Devialet retail store near the Paris Opera; it was closed but it gave me an idea. I soon had two Gold Phantom powered loudspeakers in our Paris studio apartment.
That was my hands-on…
Because the Expert Pro is such a versatile product—it's basically a music computer that incorporates everything except the music-data source at one end of the system and the loudspeakers at the other—you have to tell it what you want it to do. If you want to use a turntable, you need to set the analog inputs to phono and set the gain and loading parameters appropriate to your cartridge. If you want to use SAM to make loudspeaker-specific adjustments, you'll need to turn that on, choose your loudspeaker from a long list, and assign that function to a button on the remote control. (Because…
Sidebar 1: Specifications
Description: Remote-controlled, solid-state integrated amplifier/streaming DAC with software-assignable inputs, LCD screen, switch- mode power supply, and high-efficiency output stage. Inputs: 1 Ethernet on RJ45; 1 bidirectional USB 2.0; 1 S/PDIF on TosLink; 1 S/PDIF on miniTosLink; 1 pair RCA jacks assignable to MM/ MC phono, line, or two S/PDIF digital inputs. Main outputs: 2 pairs of binding posts. Other inputs/outputs: trigger, SD card (for configuration and firmware). Supported formats: up to 32 bits/192kHz PCM via USB; up to 24 bits/192kHz PCM via Ethernet…
Sidebar 2: Associated Equipment
Analog sources: Thorens TD 124 turntable (reconditioned by Schopper AG), Thomas Schick 12" tonearm; Ortofon Xpression cartridge.
Digital sources: Intel NUC computer running Roon Optimized Core Kit; Synology DS918+ DISKSTATION 4-BAY Network Attached Storage device, aka NAS with 4 WD 4TB Red 5400 rpm SATA III 3.5" Internal Hard Drives and my TP-Link 8-Port Gigabit network switch (unmanaged); Pro-Ject CD Box RS2 T CD Transport; Mytek Brooklyn Bridge Streaming DAC.
Preamplification: Auditorium 23 Standard step-up transformer, EAR 834P phono preamp,…
Sidebar 3: Measurements
I measured the Devialet Expert 140 Pro using my Audio Precision SYS2722 system (see the January 2008 "As We See It"). The amplifier as received was set to "High Pass 10Hz, Max. Level 2.0V." I usually precondition amplifiers by running them at one-third power into 8 ohms for an hour, which is thermally the worst case for a class-AB output stage. As the Devialet has a (partly) digital output stage, the preconditioning wasn't necessary. Nevertheless, the amplifier ran warm, with the top panel measuring 119.9°F (48.9°C) an hour or so into the testing. The menu's…
“Musical scavenger” Bryce Dessner, the composer/musician who gained fame as principal songwriter of American rock band The National, describes his process as collecting sounds that appeal to him and trying them out. Classically trained, he’s one of a growing number of artists whose cross-genre music, when performed by string quartets, orchestras, and ensembles, has been central to broadening the definition of classical music in the 21st century. Dessner is also one of eight “extraordinary artists, thinkers and doers” appointed to a collective that will help steer conductor/composer Esa-Pekka…
