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High-Quality Stereo Digital-To-Analog Converter, Pt.1

Are you listening to CDs via your DVD player? Does your DVD player have average sound quality or worse, cause buzz and hum problems when hooked up to your hifi system? Either way, you need this high-quality Stereo Digital-To-Analog Converter (DAC) to get first class sound and zero hum.

Pt.1: Design by NICHOLAS VINEN


Signal-To-Noise Ratio: -108dB (unweighted, 22Hz – 22kHz); -114dB (A-weighed),  both with respect to 2V RMS

Total Harmonic Distortion: <0.0018% @ 1kHz and 2V RMS

Channel Separation: -105dB @ 100Hz & 1kHz; -85dB @10kHz; -73dB @ 20kHz

Linearity: within 1dB @ -90dB

Frequency Response: +0.0, -0.15dB, 20Hz-20kHz

Supported Sample Rates: 28-108kHz

Supported bit depths: 16-bit, 20-bit & 24-bit

Supported Channel Formats: stereo PCM

Clock Jitter: jitter tolerant; clock jitter is typically less than 50 picoseconds

This 24-bit, 96kHz-capable stereo DAC provides sound quality equal to the best high-end CD players, regardless of price. It has one coaxial
S/PDIF input and two TOSLINK (optical) inputs, to which you can connect a DVD player, set-top box, DVR, computer or any other source of linear PCM digital audio. It also has left and right RCA sockets for connection to a stereo amplifier or home theatre receiver.

If you already own a DVD player of average quality or better, you can hook it up to this DAC and immediately upgrade the sound quality. Most DVD players have mediocre audio quality from their audio outputs, especially in terms of distortion (see “DVD Players: How Good Are They For HiFi Audio?” – SILICON CHIP, October 2007).

So why are typical DVD players so poor in audio performance? Partly it is because they are designed down to a very low price and while their on-board DAC might be quite a reasonable component, the supporting circuitry has been cut to the bone in order to keep the overall price as low as possible. It is also true that many cheap (and not so cheap) DVD players are plagued with quite strong extraneous RF in the audio outputs, mainly related to the video output signals that they continuously produce, regardless of whether they are playing DVDs or CDs.

In addition, virtually all DVD players, except the most expensive models, use switchmode power supplies. These have the advantage of being very efficient and especially with respect to recent models, have very low standby power consumption. The drawback of switchmode power supplies is that they produce lots of switching harmonics which can also get into the audio outputs.

Finally, because all DVD players these days are double-insulated and come with 2-core power cords, they inevitably cause hum and buzz when connected to the audio inputs of high-fidelity amplifiers which are usually earthed via a 3-core mains cord. There is no simple way to fix any of these problems but this new DAC project fixes them all and provides first-class audio performance to boot.

Main features

Our prototype DAC is housed in a one-unit high rack-mount case. The front-panel controls are just an on/off switch and three LED-illuminated momentary pushbuttons.

In operation, the DAC scans for a valid signal on one of its three digital inputs and when one is detected, it immediately locks onto it and works. Alternatively, you can select the wanted input signal by pressing the relevant button or you can do it with a Philips RC5-compatible remote control (such as most universal remotes) which can also be used to control the volume from the left and right outputs.

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