ANALOG DOMAIN DAC1 DAC IN DEPTH INFO

The Analog Domain DAC1 is a high performance state of the art digital to analog converter designed for faithful reproduction of digitized music. It will accept all current and future digital formats up to 192kHz/24bits over S/PDIF and AES/EBU, and up to 384kHz/32bits and DSD64 (1x), DSD128 (2x) and DSD256 (4x), over USB.

Our focus has been on maximizing the DAC1’s performance with existing recordings while ensuring compatibility with high resolution formats. It’s worth noting that contemporary recordings in “native” mode are mostly done at 96kHz/24bits or lower, rarely at 192kHz/24bits and even less so at DSD128 or above. The vast majority of recorded music is down sampled to 44.1 kHz, 16 bits. Maximum performance of the DAC1 will be obtained with higher resolutions, of course.

Yes, we do things differently in the DAC1, and for a reason:

All input data, regardless of its format, is converted to 24 bits and asynchronously resampled at a very high rate. DSD is unpacked, converted to PCM and resampled. The resampled data enters a Digital Filter which is configured in optimal mode for the output format of the Sample Rate Converter, therefore there are no user-selectable filter modes. Data from the digital filter then enters the DAC stage where it is converted into an analog signal by a state of the art precision 24-bit D/A converter with third order sigma delta noise shaper and 31 level quantizer for super low total harmonic distortion.

Jitter essentially loses its meaning in this configuration. The Asynchronous Sample Rate Converter takes care of proper word alignment and timing during conversion. The three digital blocks are synchronized to a single, high precision clock to ensure perfect timing. Any CD transport can be used with the DAC1, not requiring external re-clocking from the DAC1.

The actual DAC stage is a differential output (balanced) design. Its residual distortion is approximately 0.00035% at full scale output, consistent for all input formats. At typical output levels of -10dBFS the distortion falls off to 0.0001% (-120dB) and becomes essentially zero at levels below -20dBFS, “lost in the grass” as we say, at -130dB.

This matters! It’s during the quiet passages that DAC distortion becomes most noticeable. One bit is lost with every 6dB reduction in level, therefore a 16-bit DAC will be working effectively at 14-bit resolution or less most of the time. This is the reason why early designs created a bad reputation for digital audio.

So, is 130dB enough? It is more than enough, and here’s why: a signal which is -130dB lower relative to the full scale output voltage of 2Vrms has an amplitude of 3 million times less, or 0.7 microvolts. That is less than many amplifiers’ input-referred noise voltage. We can confidently say that the DAC1 will have an insignificant noise or distortion contribution, if any, to the signal chain.

1. Note that the vertical scale is normalized to “0” for the fundamental tone to improve display accuracy, therefore the noise floor will appear to rise as the signal becomes lower. In reality the noise floor is at a constant level. The measurements were performed with USB input, no FFT averaging.

Most other DAC’s nightmare modes5:

5. Note that the vertical scale is normalized to “0” for the fundamental tone to improve display accuracy, therefore the noise floor will appear to rise as the signal becomes lower. In reality the noise floor is at a constant level. The measurements were performed with USB input, no FFT averaging.