Help with Rigol DG1022 generator please

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The attachment shows the output (channel 1 overlaid by channel 2) of the Rigol RG1022 function generator. Channel 1 is set to 1k sine and 1Vrms. Channel 2 settings are copied from channel 1. The output from the generator goes into a Focusrite Scarlett 2i2 and displayed in ARTA software. I'm physically moving the output connection from CH1 to CH2, and using the same input on the 2I2.

So what is the noise/distortion on CH2 between 100hz and 5khz? Hopefully it's something simple I'm overlooking.

Img.jpg
 
No, I'm not sure. If the output of the function generator is exactly the same for both channels, I can't imagine why CH 2 would overload the input of the sound card and Ch 1 wouldn't. I'll check the outputs with a multimeter to make sure sure I'm getting the same voltage out of both channels.
 
Are you sure your soundcard input is not overloaded/limiting?

Yes, now I'm sure. The outputs of the Rigol DG1022 are exactly the same in frequency and amplitude. Besides there's a light around the gain knob that turns red when you overload the input.

Attached are separate pics of the two output channel. You can see that the THD is different on each channel.

Rigol DG1022 CH1.jpgRigol DG1022 CH2.jpg
 
Looks to me like, not harmonic distortion, but low frequency noise.

If it had spikes at 60Hz and multiples, power line.

It appears to be just random. This could be a chip with dirty silicon, or an input which has been abused ("Zenered").
 

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