dCS Bartók APEX Headphone DAC

The Headphone DAC is the version of Bartók APEX that most headphone listeners buy, and it differs from the standard model in one respect: a headphone amplifier on the front panel, with a 4-pin XLR balanced output and a 6.35 mm jack, driven from the same Ring DAC APEX. The converter is the dCS design shared with Rossini and Vivaldi, a thermometer-coded array of equal-value current sources switched by 48 latches under an FPGA mapper, so that each sample is produced by a different combination of sources and component errors are spread as random noise rather than appearing as distortion. The APEX board of 2022 lowered the impedance of the reference supply feeding those sources, improved the symmetry of the summing stage and introduced a new compound-amplifier output stage; dCS quotes more than 12 dB better second-harmonic linearity and a lower noise floor than the previous board. The headphone amplifier itself operates in Class A, in balanced or unbalanced mode, and is specified at 1.4 W rms into 33 Ω and 0.15 W into 300 Ω, with four gain settings to suit anything from sensitive planars to 300 Ω dynamics; 33 Ω is the minimum rated load.

Herb Reichert's Stereophile review of the Bartók APEX, which made it the magazine's 2023 Digital Source Component of the Year, found it "unquestionably smoother, less grainy, and more powerful sounding" than the original, with a "wet feel to its clarity"; his earlier follow-up on the first Bartók Headphone DAC had already singled out its filters and crossfeed for headphone use. Neil Gader in The Absolute Sound heard "a weightier unmovable foundation" and an airier, "wetter" sense of ambience from the APEX version. For headphones, the Expanse processing is the addition that matters: two settings (E1 and E2) widen the stereo image ahead of a delayed crossfeed stage so that a mix sits in front of the listener instead of inside the head, while leaving the recording's reverberation and the headphone's own character alone. It is switched from the Mosaic app and suits some recordings better than others.

As a source the Headphone DAC is identical to the standard Bartók APEX. Ethernet carries Roon Ready, TIDAL, Qobuz, Spotify Connect, Deezer, internet radio, UPnP and AirPlay through Mosaic, with full MQA decoding on the network and USB-B inputs. The asynchronous USB-B input accepts 24-bit/384 kS/s PCM and DSD128, a USB-A port plays from a drive, two AES/EBU inputs run singly or as a Dual AES pair to 384 kS/s, and S/PDIF is on RCA, BNC and Toslink. Balanced XLR and unbalanced RCA line outputs are switchable between 0.2 V, 0.6 V, 2 V and 6 V full scale, so the same unit feeds a loudspeaker system through a preamplifier or directly into power amplifiers, with headphones plugged in when wanted. Two word clock inputs take a Lina or Rossini Master Clock, and a word clock output lets the Bartók act as master for a transport.

Within the dCS range this is the one-box headphone system; the alternative is the three-box Lina stack of Network DAC, Master Clock and Headphone Amplifier, whose separate amplifier offers 2 W into 30 Ω, three inputs and three output connectors, at a combined $32,300 against $24,100 here. Above it, Rossini APEX and Vivaldi have no headphone outputs of their own. The Headphone DAC is available to order; ask us to arrange an audition, and to set up the standard Bartók APEX DAC so the shared DAC section can be heard first.