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RE: [linrad] RE: Silly question or is it?
> Also my uncalibrated system at the moment shows a big nasty spur
> at 48khz or so, does the calibration routine remove it? If so how?
Then something is wrong. You should have an ugly looking peak
at 48kHz but it should not be big. How it looks depends on the
bandwidth. It should be somewhere 10 to 30 dB above the noise floor.
There is 1/F noise (flicker noise) in the A/D converter. In a Delta44
there is a digital filter that removes signals below about 10 Hz
but still there is a lot of noise at very low frequencies.
Ill designed soundcards (original shape of Delta44) may pick up
low frequency interference, 50Hz and other low frequencies that
are present in the form of currents in the PC chassis.
If you set a bandwidth of 10 Hz, deselect fft2 and zoom in the
spectrum you will see if there are narrowband components like
50 Hz or if there is only the 1/F noise.