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PhaseNoiseComparison
www.diyaudio.com/community/threads/asynchronous-i2s-fifo-...
1.To compare phase noise, oscillators have to be at the same frequency.
2.45.1584MHz is selected for the comparison because 45/49 MHz clocks can cover the full digital audio ranges from 44.1 to 384KHz
3.SC-Pure phase noise was measured recently by a calibrated E5052 phase noise analyzer from a third party.But all other phase noise numbers are collected from published datasheets or websites.So please correct me if there is anything wrong.
4.No doubt, phase noise numbers have a big impact on the DAC sound quality, but it may not be 100% related.It could be because of the limitation of the fundamental frequency only phase noise measurement method. DAC runs by the square wave clock, not the sine wave. However, each harmonic frequency has its own phase noise and they all contribute to the final phase noise of the square wave clock. That’s why clocks with the similar phase noise numbers could still sound differently.
5. I could be the one who did the most listening tests to different clock oscillators besides Doede. Based on my own experiences of the listening tests, I've found that the close-in phase nose, the phase noise floor and the phase noise in between (Leeson’s equation applied) are all significant to the sound quality. An oscillator can not achieve a higher grade sound quality if it doesn’t have good close-in phase noise even though its noise floor is great. On the other hand, a good close-in phase noise oscillator can also sound a bit fat, less sound stage any dynamic if the noise floor or the phase noise in between are not great.
6.45.1584MHz Neutron Star2 is a pretty expensive clock. But I found it just uses a fundamental non SC-CUT cut crystal (not the 3OT SC-CUT) . It does have a heater on the PCB but just to keep the crystal temperature stable at around 40 degree C regardless of the ambient temperature. Don’t know why NewClassD didn’t publish the phase noise specifications.
7. Normally SC-Cut crystal oscillators have both better overall phase noise performance and better sound quality than AT-Cut crystal oscillators.
8. Limited by the noise floor of a phase noise analyzer, oscillators with great far off phase noise may not correctly show from the measurement results.
PhaseNoiseComparison
www.diyaudio.com/community/threads/asynchronous-i2s-fifo-...
1.To compare phase noise, oscillators have to be at the same frequency.
2.45.1584MHz is selected for the comparison because 45/49 MHz clocks can cover the full digital audio ranges from 44.1 to 384KHz
3.SC-Pure phase noise was measured recently by a calibrated E5052 phase noise analyzer from a third party.But all other phase noise numbers are collected from published datasheets or websites.So please correct me if there is anything wrong.
4.No doubt, phase noise numbers have a big impact on the DAC sound quality, but it may not be 100% related.It could be because of the limitation of the fundamental frequency only phase noise measurement method. DAC runs by the square wave clock, not the sine wave. However, each harmonic frequency has its own phase noise and they all contribute to the final phase noise of the square wave clock. That’s why clocks with the similar phase noise numbers could still sound differently.
5. I could be the one who did the most listening tests to different clock oscillators besides Doede. Based on my own experiences of the listening tests, I've found that the close-in phase nose, the phase noise floor and the phase noise in between (Leeson’s equation applied) are all significant to the sound quality. An oscillator can not achieve a higher grade sound quality if it doesn’t have good close-in phase noise even though its noise floor is great. On the other hand, a good close-in phase noise oscillator can also sound a bit fat, less sound stage any dynamic if the noise floor or the phase noise in between are not great.
6.45.1584MHz Neutron Star2 is a pretty expensive clock. But I found it just uses a fundamental non SC-CUT cut crystal (not the 3OT SC-CUT) . It does have a heater on the PCB but just to keep the crystal temperature stable at around 40 degree C regardless of the ambient temperature. Don’t know why NewClassD didn’t publish the phase noise specifications.
7. Normally SC-Cut crystal oscillators have both better overall phase noise performance and better sound quality than AT-Cut crystal oscillators.
8. Limited by the noise floor of a phase noise analyzer, oscillators with great far off phase noise may not correctly show from the measurement results.