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Measurement |
Parameters |
Left |
Right |
Microsoft PC98 Advanced Audio Recommendation |
Line in/Line out |
Freq. Resp |
10-30kHz |
10-30kHz |
20-20kHz or beyond |
SNR |
95.9dB |
95.8dB |
³ 85dB | |
THD+N |
0.003% (-90.5dB) |
0.003% (-90.4dB) |
£ -65dB | |
Crosstalk |
86.5dB |
86.0dB |
³ 65dB | |
| Mic in/Line out |
Freq. Resp |
10-30kHz |
10-30kHz |
20-20kHz or beyond |
SNR |
79.1dB |
78.9dB |
³ 75dB | |
THD+N |
0.01% (-80dB) |
0.01% (-80dB) |
£ -55dB | |
ADC (Line In Record) |
SNR |
84.0dB |
84.3dB |
³ 80dB |
THD+N |
0.015% (-76dB) |
0.015% (-76dB) |
£ -60dB | |
DAC (Line Out Playback) |
SNR |
93.3dB |
93.9dB |
³ 85dB |
THD+N |
0.015% (-76dB) |
0.016% (-76dB) |
£ -65dB |
Analog to Analog loopback FFT
Audio precision output connects to line-in of sound card and line-out sampled and measured by the AP. (Sorry if you can't see it properly - will try to get a better contrast.) The 1kHz signal is measured at -3dBFS. The aim is to get the lowest possible harmonics - as seen here the 2nd harmonics is just below -100dB.
Analog loopback noise floor. A -60dBFS 1kHz signal excites the codec to bring it out of sleeping (some codecs report very very low noise floor by swithcing off when there's no signal present and hence isn't accurate - a -60dBFS signal is injected to wake it up, and then notched out (filtered out) when measurements of noise floor is done.
Analog to Digital FFT
Sine wave is pumped into the sound card, recorded and played back thru an S/PDIF output. These graphs show the quality and noise performances of the Analog to Digital Converter (ADC).
Digital to Analog FFT
These graphs show the performance of the Digital to Analog Converter (DAC), which is essentially the most important part of the circuitry that converts your PCM data to audible analog audio. All your mp3, wav, and other digital data are converted and fed to the DAC to output audio.
*Terms used:
FFT : stands for Fast Fourier Transform. This is a method to transform signals in the time domain to the frequency domain (as can be seen in the frequency for x-axis in the graphs above).
dBFS : dB is decibels which is a term used to measure sound amplitude in the logarithmic scale. FS stands for full scale. 0dBFS is found when the volume is increased to the point of signal clipping; then -3dBFS is measured relative to this datum.
Frequency Response : The amplitude of the signal at each frequency throughout the entire audible frequency range. The measured frequency response here is a straight line from 10Hz to 50kHz (excellent frequency response - the larger the better), so not much fun to look at.
SNR : Signal-to-Noise ratio. As the name says, it's the ratio of the amplitude of the signal to the amplitude of noise.
THD+N : Total Harmonic Distortion plus noise. Total Harmonic Distortion refers to the distortions introduced by the series of individual harmonics, and Noise is the inclusion of noise in the measurement.
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