Best Cable Option: Streamer to DAC
kijanki It is likely that harmonics of 22kHz come from percussion instruments, that are not continuous by nature.Any percussion instrument is an "continuous" as any violin or other instrument. Consistent with the Fourier Transform, this wave can be recorded. ... 100Hz (drum roll) will give you (modulated) 22kHz with bunch of sidebands spaced 100Hz apart ... Sidebands appear because signal is modulated (not continuous).The signal is analog, it is continuous. The danger here is that anything above half of sampling frequency will, in D/A process, fold into 0Hz and up ...Anything exceeding half the sampling rate is filtered out as part of the A-D conversion process. It doesn't "fold" into anything. You can easily prove this with measurements. |
Any percussion instrument is an "continuous"No, it is not. If you record drum roll it will show individual bursts with silence in between. The signal is analog, it is continuous.Analog and continuous are two different terms. When you strike drum once signal is not continuous. There is a silence before and after. Any modulated frequency will show on FFT as a root frequency and sidebands. It applies not only to amplitude modulation, but to any modulation, including time jitter of digital signal. Anything exceeding half the sampling rate is filtered out as part of the A-D conversion process. It doesn’t "fold" into anything. You can easily prove this with measurements.There are analog filters before A/D process but they cannot be very sharp. By definition they have to be even group delay (Bessel), and those are very hard to make in analog domain. Bessel filter characteristic show practically the same, weak attenuation within 2x Fc, no matter how many poles you use. The whole idea of single bit converters (Delta-Sigma) was to avoid sharp filters by pushing quantization noise higher. In any A/D and D/A process there is ALWAYS something that folds over. The only issue is the scale (amplitude) and all I stated is that Nyquist applies only to non-interrupted (continuous) frequencies, but artifacts of this violation are likely non-audible with redbook CD and definitely non-audible with 96kHz sampling. |
kijanki ... If you record drum roll it will show individual bursts with silence in between ... When you strike drum once signal is not continuous. There is a silence before and after ...It isn’t clear why you think percussion instruments are not "continuous." They're as continuous as a trumpet - every trumpet player runs out of breath eventually. There’s nothing especially unique about the analog wave produced by percussion instruments. There are analog filters before A/D process but they cannot be very sharp.That something is not perfect does not make it useless. Filters used in A/D conversion can be measured to show essentially perfect rejection of frequencies that would violate Nyquist. ... Nyquist applies only to non-interrupted (continuous) frequencies ...Nyquist and Fourier Transform apply equally to percussion, trumpet, violin and other sounds. Consider that Nyquist is not a theory - it’s a theorem. |
Again, any signal that is amplitude modulated will have sidebands. Organ note played will show single frequency on FFT, but interrupted 10 times a second will show root frequency and sidebands spaced 10Hz apart. I have to agree with you, that filters in front of A/D will be essentially perfect. I forgot that they record at 192kHz (not 44.1kHz) and 10 pole Bessel will have, at 10x Fc, attenuation above 100dB (below one bit of resolution). |
