Hi Alex, I have 2 350v3's and both have the similar problem, I really need the schematic, if you could please send it to <snip>. Mackie is very uncooperative and wants $200 for the whole module when the problem is obviously the pre amp.I see. Unfortunately in my case the whine is there right from the beginning, I'll check out those parts anyway, I might be lucky.
If you can share an email address I'll send you the service manual which is for both 350/450v3
Alex
Thank you, RZ
Moderator edit: New thread created from this. Email address removed to prevent spam.