There exists many of audio DACs but all are variants of two basic types. It is R-2R or DAC with DELTA-SIGMA modulator. R-2R is assembled from very precise resistors and thank to this is harder for manufacturing and is much more expensive. It can be operated in Non Oversampling Mode (NOS). Disadvantage is that his sample frequency is near to audio spectrum and is hard to filter it with simple low-pass filter. When we run DAC without filter with high quality components that sample frequency pass to the tweeter and theoretically can overload them. This problem is solved in DAC with oversampling because sample frequency is moved up and can be simply filtered. Unfortunately this solution is much sensitive to jitter on clock signal which we can hear at listening. Next disadvantage is that in oversampling with using FIR or IIR filters are in a sound created a new frequency products which was not in original record. Result is that from a record is partially lost space and location of instruments. This is the reason why majority of HiFi listeners prefer R-2R type DAC in non-oversampling mode.
DAC parameters like THD+N or noise are measured with a sinus signal. In measurement results looks DACs with DELTA-SIGMA modulator very nice. For other shapes it is not too great and listening tests tells that R-2R DACs sounds better. I measured several DACs and take pictures of his shapes from a oscilloscope screen. I measured them at 48kHz sample frequency. Maximum theoretical frequency is 24kHz. I measured them at 240Hz, 2.4kHz and 24kHz. I choosed divisor of sample frequency because trigger in oscilloscope. Shape will not travel over screen and can be easily photographed. I generated sinus, square and unit-impulse with Baudline. Shape is generated with maximum available amplitude 0dB. Some delta-sigma DACs distort signal at this level that I made test with a lower level. PCM1794A required level -2dBm without distortion and PCM5102 -4dBm. I measured shapes with FIR and IIR filter that we can see differences.
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| DAC | SINUS 240Hz | SQUARE 240Hz | IMPULSE 240Hz | SINUS 2400Hz | SQUARE 2400Hz | IMPULSE 2400Hz | SINUS 24000Hz | SQUARE 24000Hz | IMPULSE 24000Hz |
| PCM1702 0dB |  |
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| AD1865 0dB |  |
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| PCM1704 LPF 0dB |  |
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| PCM1794A SHARP 0dB |  |
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| WM8740 0dB |  |
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| PCM5102 IIR 0dB |  |
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| PCM5102 FIR 0dB |  |
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| PCM5102 IIR -4dB |  |
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| PCM5102 FIR -4dB |  |
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