I have too much noise in my signal path. While examining the causes for it, I confronted a strange phenomenon:
I plug the mic cable to the mic preamp, but do not connect a mic to the cable. Then I turn the amplification in my mic preamp up as far as it goes.
Then I tap the end of the cable (the female-end of the XLR cable) with my index finger, rather gently. It sounds like this when recording it in Reaper:
https://stash.reaper.fm/oldsb/802291/cabletest.mp3
I can hear my finger tapping the cable very clearly!
Different cables behave differently, some I need to tap quite hard in order to hear anything. It does not seem to matter if I tap the very end of the cable, or the metal surrounding the end of the cable.
Did I just invent "poor man's ultra-fast cable tester" or what is this phenomenon? Can I say that "the less there is tapping noise, the better quality the cable is"?
(OK I have some reverb in this recording too :-) but don't let it distract you)