I have the same problem..........but it's a slight buzz.....only coming from the left tek-12 or channel 1..........I think it's a mixer problem..cuase they're both grounded....it's not the amp, cause I use the amp for digital music aswell......and no problem, and to test it.....I hooked up the tables in the CD instead of phono.......it didn't resolve......probably the mixer.

peace

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tranceformed

hm...might it be the wiring? sometimes i get the buzzing, so i shake the wires which come from mixer to amp..

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Its either the ground switch that needs to be adjusted or the phono on the channel you are using...
try to use an regularly unused channel with phono and see if it humms.. if it does.. i give up..

BTW, those Mackie speakers are very very good so take care of them!

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