This week, I got annoyed by my favourite Etymotic earphones starting to sound distorted in one channel. I decided to use my lab equipment to see to investigate that distortion in mode retail.
In
this video you see how I did that both on an R&S RTB and a Siglent SDS2k scope:
After making the video, I realised that I also could have exploited the fact that the SDS can do two FTT analyses at once! To do so, I took two identical microphones (Røde M5) and treated them with the same mic pre-amp settings, then connecting them to channel 1 and channel 3 of the SDS scope (pic attached). The result shows that the 'good' channel (Orange trace, green FFT) has fewer unwanted harmonics than the 'bad' channel (yellow trace, pink FFT).
The dual FFT of the SDS is clearly an advantage over scopes that can do one FFT at the time only ;-)
Next step is to try the audio analyser on the CMU200 to investigate the distortion… And to see whether I can get it repaired, perhaps by compressed air, as someone suggested!