Oversampling is a crucial part of a modern DAC, especially the ES9038P which uses 4x oversampling in stereo or 8x in mono mode. The ES9038P has shown its ability to filter out noise that the Play allowed through. We found out this digital noise in the Play, was brought on by having 2 paths to ground. One in the USB cable and one through the chassis ground (supplied by the power supply ground).
Oversampling helps to push noise/distortion outside of the audio band, especially with modern filtering/shaping, in addition to oversampling. With specific shaped filtering you can filter out 50% more or so of the quantization noise than with a plain filter (Source: Art of Digital Audio).
In simple terms, oversampling means to sample at a higher rate than is required by the Nyquist Rate (a little over two times the top input frequency). Quantization (also called signal processing) errors happen when going from analog to digital (ADC). This involves taking a continuous signal and segmenting it into “boxes” or “bins”.
“Such errors are an inevitable result of the classification of continuously varying analog voltages into discrete digital bins. This quantization necessarily adds this noise at the level of ½ LSB (Least Significant Bit).” Pg.694 Art of Electronics Lab Manual 3rd Edition
Luckily for us, the entire process is digital. From hard drive to XMOS to ES9038P (or ES9018K2M for the Play), where finally, digital is then turned to analog (DAC) and sent into an amplifier. Now, if you were using a record player, you wouldn’t need any DAC to play it back, it’s already analog.
Often after conversion from digital to analog (DAC), flat lines will have a roughness, also called “steppy edges”. This error can be smoothed out using a quality, low-pass filter. If you look on the underside of the Play’s lid, this is what the “LP” means in the diagram. Op-amps are commonly used to create quality low-pass filters, with just a little effort.
However, you can also clean up this noise by simply increasing the bit depth (usually 24-bit or 32-bit for HiFi DACs). Bit depth refers to how much data is stored in each sample. In other words, raising bit depth increases the amount of information per period/cycle.
Increasing the sampling rate changes the number of data points per second, thus increasing your sound resolution and accuracy. Here you can see how sampling rate vs. oversampling plays out. Thanks to Rynsin, over on SuperBestAudioFriends Forums. (Click for full thread)
Sampling Rate: Sampling involves breaking the waveform/graph into smaller and smaller chunks. However, the sampling rate must be taken across the horizontal/time axis.
Table of Contents:
- Review Main Page
- Competition Hardware Descriptions:
- Review Hardware Info v2
.0 vs. v1 .6 Burson Audio Play:
- Digital Noise/Mouse Distortion + Solution: (USB Ground Headaches)
- Opening Thoughts on Voicing of Burson “Play” vs. ES9038Pro:
- Listening Tests Streaming: ES9038 on Coax + RCA out
- A Closer Look at Oversampling & Noise Filtering: (It’s Not Magic!)
- Listening Test Music (
Pt1): (Adele with ES9038P on I2S)
- Listening Test Music (
Pt2): (Tedeschi Trucks Band with ES9038P on Coax)
- A note on Converting PCM to DSD with Foobar2000: (DSD64 Clicking)
- Balanced vs. Unbalanced: (Understanding the ES9038’s Performance)
- Adding I2S Input To ES9038 DAC: (Power Tools and Soldering Irons)
- Measurements/Technical Page
- Closing Remarks: (The Verdict)