The only exact way i can phrase it is later firmware versions may tweak it.
Thats possible. I'm using old model SDS1102X and when I flashed firmware to the latest version, I got unexpected result.
Usually I'm using oscilloscope for spectrum analysis, by recording large raw sequence and then processing it with FFT on the PC. I'm using FFT with 1-4 million points, so it very sensitive. With latest firmware I got a lot of distortions.
It was below -80 dB, so in the time domain the difference is not significant.
Here is firmaware 2.13R5 (which works good):
![](https://i.imgur.com/q9vEd0X.png)
And here is firmware 2.15R10:
![](https://i.imgur.com/5mmDJnO.png)
But in the frequency domain it looks much worse:
![](https://i.imgur.com/YFIxVlc.png)
I'm not sure why it happens, but these artifacts was added at the time when Siglent released new X-E model. So, I think they both may share the same signal processing algorithm.
After all, I didn't find the way to fix it and since I need clean spectrum, I rollback to the old 2.13R5 firmware. It helps and distortions disappears
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/smiley.gif)
So, the firmware change may lead to significant change in measurement results.
It will be very interest if someone can check if this issue exists on X-E model with latest firmware.