TAS 194: Weiss Engineering Jason CD Transport and Medea D/A Converter

Transports Do Make A Difference

Take a cleaver and hack a CD player into two functional halves. What you end up with is a transport and a digital-to-analog converter (DAC). Is that really necessary? Is there a good reason to break an integrated CD player, which is bound to be a more cost-effective design, into two pieces? The most compelling reason is flexibility—the ability to experiment with new DAC designs as digital technology continues to evolve. Having lived with the Jason for some time now, I am convinced that a good transport is essential to laying the foundation for a sonically superior digital front end. The notion, popular in some circles, that a good DAC can overcome the limitations of a mediocre transport gets crushed by the Jason. But then this is no ordinary transport.

The Weiss Engineering Jason was built without compromise in either electronics or software to partner with not only Weiss’ own Medea DAC but any DAC or digital amplifier out there. At the Jason’s core is the impressive Philips CDPRO2M top-loader mechanism. Push the “Eject” button and a motor drive lifts a heavy-duty lid. Push it again and the lid closes while securely capturing the CD. As with the Medea, the chassis consists of a twin frame. The inner steel chassis provides an effective shield against electrostatic and electromagnetic fields, while the outer anodized aluminum frame is responsible mainly for heat convection and the unit’s elegant cosmetics.

Attention to detail is abundant. All sensitive voltages have dedicated regulators. The power switch activates a solid-state-based relay which only switches on or off at zero crossings of the mains voltage, ensuring glitch-free power switching. An internal low-jitter clock generates all clocking signals, including those required for the CDPRO2M transport.

In order to ensure maximum compatibility with 196kHz/24-bit or 88.2kHz/16-bit DACs, the 44.1kHz/16-bit signal from the CDPRO2M may be optionally upsampled to 88.2kHz or 176.4kHz. When upsampling is engaged, the output word-length can be set to 16, 20, or 24 bits to accommodate the word-length requirement of the partnering DAC. Word-length reduction to 16, 20, or 24 bits is performed via proprietary on-board digital signal processing using the POW-R dithering algorithm, which is the de facto standard in professional audio for this operation.

In the case of the Medea DAC or any other DAC which can accept any of the Jason’s outputs, it is possible to experiment with the various upsampling options to determine which sounds best in the context of a particular system. The Medea’s onboard DSP upsamples 44.1 to 88.2kHz, while its DAC chip upsamples 88.2 and 176.4kHz input to 352.8kHz. Thus, for Jason and Medea users, the critical step of upsampling from 44.1 to 88.2kHz may be performed either by the Jason or the Medea. According to designer Daniel Weiss, some users prefer the 44.1kHz/16-bit output from the Jason. And I can understand why. For a single cable connection (e.g., Jason AES/EBU output #4 into Medea input #3), I absolutely, positively, preferred 44.1kHz/16-bit settings. However, for a dual AES/EBU cable connection (Jason output #1 feeding inputs 1 and 2 on the Medea), 176.4kHz/24-bit was definitely king. Image outlines became more robust. Soundstage depth perspective was enhanced. In a nutshell, the music flowed with greater microdynamic conviction and analog-like spatiality; timbre accuracy, the cornerstone of musical realism, was exceptional.

The Jason also incorporates an optional DAC+ circuit whose goal it is to mask discrete jitter frequencies with wideband noise. This spread-spectrum technology is based on the premise that raising a DAC’s noise floor is sonically benign while discrete jitter frequencies are not. With the Medea as the partnering DAC, activating the DAC+ circuit made no audible difference during my listening tests. Weiss does believe, however, that it would help inferior DACs perform better.

The remote control deserves special mention. It’s solidly built and provides complete control over all of the Jason’s functions, including selection of sampling rate and word-length. The Jason’s 0/180-degree phase inversion function is worth writing home about. The ability to invert signal polarity on the fly is essential to maximizing sound quality during CD playback. The ubiquitous multitrack recording process whereby 24 or more tracks are being mixed down to as few as two stereo tracks almost guarantees that one or more tracks in the mix are reversed in polarity. And the situation may differ from track to track. Quickly checking the 0 and 180-degree settings on the fly makes it extremely convenient to select the best sounding setting for a particular track. Generally speaking, one setting gives the most focused image outlines and is the criterion I use for setting polarity.