Good try, Mr. @Axeman! 
Hey the discussion is getting intriguing⌠
@jofemodo --> âIf would check whatâs on the output of the DACâ sorry if this is a stupid question but does it mean âafter the output of the Zynthianâ?
Yes, after the output of Zynthian 
Please, specify exactly your full audio chain. What devices are connected downstream from zynthian, what order, what type of connection, etc.
Regarding your mixer, check this:
https://larryjordan.com/articles/why-i-returned-a-mackie-mixer/
I didnât read the article completely, but it seems like some Mackie products having problems with audio levels when recording to digital. Perhaps it could be related âŚ
Regards,
@jofemodo --> thanks! my full audio chain is:
Zynthian -> RCA LR out or Jack LR out (I get the same noise from both) to -> Mackie 1202 VLZ4 tried all the inputs/channels (and nothing changes with a different mixer: I tried also with a Thomann the t.mix mix 802), Iâm listening through my old Sony headphones or through a couple of KRK RP6 Rokit (headphones connected to the headphones out, monitors connected to the main output XLR), thatâs all.
Reg the article: itâs about the old Onyx series - analog mixers with integrated digital interface, the 1202 VLZ4 is just a simple analog one and, after all, with another mixer the problem persists⌠
Have you tried the alsamixer from Zynthianâs command line? There are a few options there (although the default should be OK).
These options include things like âautomuteâ feature, etc. Iâve playing with this features, but i canât reproduce your problem. Anyway, perhaps you can use it to solve it 
Regards,
@jofemodo THANK YOU!! 
I took a look at alsamixer and yes - the problem was there: the âAutoMuteâ function was on, turned it off and now the noise is gone!
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