Occasionally, crystal oscillators may be necessary for digital audio processing. China makes a lot of crystal oscillators, low and high frequency. They are good, however, their datasheets are far from normal.
Here is some information and tests on these :
https://drive.google.com/drive/folders/1Upn6FwOYexZBSDs3dr4gCHoRx7ajs_De
Here is some information and tests on these :
https://drive.google.com/drive/folders/1Upn6FwOYexZBSDs3dr4gCHoRx7ajs_De