I think he talks about a "mechanical" sound, not from the electric signal.

Am 11.12.18 um 17:40 schrieb Diego Ragnini diegora@... [Doepfer_a100]:

What is the module concerned by this sound output The one you hear the sound from, I mean… Or just any module featuring an audio output jack

Il giorno 11 dic 2018, alle ore 17:33, kazys varnelis kvarnelis@... 1 < Doepfer_a100@yahoogroups.com > ha scritto:

Hi I have a P-9 that makes a high pitched sound at the edge of my hearing (12-13000Hz or so). I have three others, none of them make it. It decreases as I unplug modules, but with half of them unplugged, it is still faint. It doesn't appear to be any module in particular. The bus board reads version 5/2008. 

Any thoughts