more distortion from REW than from Arta - signal generator

[smileday]

I don't understand why "digital" signal generator are different.

REW generates more distorted signal than Arta.

The attached pictures show the results of 500Hz sinusoidal signal generation.


REW 0.0017%THD

Arta: 0.0010% THD

 

[sam_adams]

You have the graph in ARTA measuring the distortion in dBFS and the graph in REW measuring in SPL. The cursor in ARTA is set at 20.51 Hz and the cursor in REW is set to 60.3 Hz. If you wish to see the distortion at the stimulus frequency in REW while using the RTA, click the 'Show distortion' button to open the distortion display pane. You should also check the 'Lock frequency to RTA FFT' checkbox in REW so the stimulus frquency is in the center of the FFT bin.

 

[smileday]

Windows 10, REW V5.20 (REW is up to date at the time of this posting)

On Sound Control Panel on Windows 10, everything (used or unused) was set to 48kHz sampling rate.

 

[smileday]

Cursor position does not affect signal generation or THD measurement.

Can anyone use two computers? One computer just generating signal from REW or Arta, from one at a time. The other computer only measuring the signal. I guess there will be difference in THD. The sine signal from REW will have about two times higher THD than that from Arta.

 

[John Mulcahy]

On Windows Java drivers only handle 16-bit data, use ASIO drivers or an ASIO wrapper like FlexASIO or ASIO4All to get the full resolution of the interface. You should also add dither in the REW generator at the appropriate bit depth for your interface.