Unofficial Mackie User Forums > DL1608/DL806/DL32R/ProDX Mixers

Pin One Problem on DL1608

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WK154:
RR don't put this under auxes!
I didn't think I would see this showing up in any new Kit, but Mackie has done it. I misplaced my old hummer so I had to wait for the parts to arrive and they did today. Placed one lead on chassis (the one you have to bring out by the PSW connector area) and the other to any  XLR Pin 1 or sleeve on the Auxes and it hum's like a bumble bee. Need any more proof? I'll record it later. The other power supplies fixed the problem. Lucky for Mackie and those who bought a DL. Let's see if Mackie will ante up and send out replacements? APX has the correct PSW or certainly can provide it. Probably should notify Mackie officially and wait for their excuses. Mackie Lurkers?

RoadRanger:
Are you trying to tell us that you have found a power supply that has the AC ground connected to the minus but doesn't have pin 1 issues? I'd love to be wrong in my belief that the noise problem is inherent to the tying together of the AC ground and the minus in the power supply !

For those wondering what the hell he's talking about (and for the Mackie "engineers" who seem to be oblivious):
http://pin1problem.com

WK154:
I guess you haven't been understanding the posts. That is exactly the problem Safety ( Chassis) ground on the DC power return. It is a direct execution of what is called common impedance coupling.  The noise is also fed to the DC to DC converters, 48V, +- 15V and 3.3V come to mind all from 12V DC. Why don't you try it with a hummer?.

RoadRanger:
I'm just not following you. If the problem is as I said how can any power supply swap fix it assuming said power supply still brings the safety ground out to the mixer via the minus lead?

WK154:
Are you trying to tell us that you have found a power supply that has the AC ground connected to the minus but doesn't have pin 1 issues?
No where did I make that statement?
If the problem is as I said how can any power supply swap fix it assuming said power supply still brings the safety ground out to the mixer via the minus lead?
Because the power supplies don't bring the safety ground to the minus lead into the mixer (except for Mackie's). It's called isolation. If you want to keep the chassis from floating then you need to tie it to safety ground but not thru the power supply and in as direct a path as possible and after the DC to DC converters. You cannot eliminate ground currents into other devises that are attached but you can minimize the effect on their performance. As someone once said "electrons don't read schematics".

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