No other sampling rate was used, but before sampling the audio signal had to pass through anti-aliasing low-pass filters. In the beginning, it was extremely ex

No other sampling rate was used, but before sampling the audio signal had to pass through anti-aliasing low-pass filters. In the beginning, it was extremely expensive to make analog low-pass filters that were steep enough to block frequencies over 22 kHz, but to pass those under 20 kHz. So many audio-to-digital conversions used cheaper anti-aliasing filters, with a narrower pass-band, which could be significantly lower than the 20 kHz promised by the CD technology. The CDs mastered in this way had a worse quality than claimed. Even today, such analog low-pass filters would be too expensive, which is why now everybody uses much higher sampling frequencies for audio, like 192 kHz. If a 44.1 kHz digital stream is desired, it is obtained through digital filtering and decimation, which are free of the constructive problems of analog filters. But higher sampling frequencies where impossible in the early years of CDs, when the existing 16-bit ADCs barely reached 44.1 kHz. Moreover, 16-bit DACs were very expensive, so the cheaper CD players used DACs with a lower resolution, like 14-bit DACs, which further reduced the quality of playback. So for some years in the beginning, typical CD quality was not as good as advertised and as demonstrated by using equipment much more expensive than what was typical for consumer players or even in the recording studios with smaller budgets.