KRELL K-300i

The most important design feature is that the K-300i incorporates Krell’s proprietary iBias circuit, which monitors current flowing through both the positive and negative halves of the K-300i’s output stage and makes sure that the inactive half, that would otherwise switch off in a typical Class AB design, receives some minimum current. This way the inactive half never switches off completely and does not create switching distortion. It also means, according to Krell, that the amplifier’s operation is not affected by speaker impedance and operates in Class A for the first circa 90W, then it switches into AB up to 2x150W into 8 ohms or 2x300W into 4 ohms. This also means that the Krell takes 46W of power even if no signal is present on its speaker terminals.

I found interesting that Krell does not recommend to use power filters in the powerline that is feeding the K-300i. The company explains that beefy power supplies have always been the heart of their amplifiers and the filter should handle (in case of the K-300i) the peaks of 750W not to limit current.

In its standard version the K-300i is just a good old analogue amplifier. However, there is an optional digital module that turns it into a modern digital hub. The digital module adds ESS Sabre Pro based DAC that facilitates network streaming of AAC, ALAC, AIFF, FLAC, WAV, WMA, and DoP files up to 192kHz/24-bit from UPnP music servers or NAS devices. Via mconnect Control App (for Android and iOS) one can stream from Spotify, vTuner, Tidal, Deezer, and QoBuz, and is Roon and MQA friendly. HDMI 2.0 inputs and output supporting 4K UHD with HDR are available for TV viewing with audiophile grade sound quality. A USB port on the front panel plays music from USB flash disks, another USB port on the rear panel makes streaming music directly from a computer possible. The digital option also includes, optical Toslink and coaxial inputs, and a Bluetooth receiver featuring Qualcomm aptX connection technology.