I got a Mackie SRM150 for stage monitoring but I'm having problems getting a good connection in the hybrid-XLR jacks on the front with a 1/4 inch jack guitar cable. Even when it feels like it's firmly placed, I'll still get periodic thumps through the speaker.

Anybody have any suggestions? I've already exchanged one unit for another and I've swapped any number of guitar cables but the problem remains.

  • How did you eliminate the other end of the cable as a possible cause of the problem? And is the input meant to accept unbalanced high impedance signals? – Todd Wilcox Oct 27 '16 at 3:34
  • The phonos are the red and white inputs. The problematics are XLR/ standard jack. – Tim Oct 27 '16 at 7:35
  • Are you certain the problem occurs equally with both jack inputs? (Just want to rule out whether one if the connectors is faulty.) – Andy Oct 27 '16 at 8:55
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    I've switched between multiple cables. The input is meant to carry high impedance or mic signal. Problem occurs with first jack. It's almost as if the jacks aren't quite long enough. It's used as a monitor between instrument and feed to the sound mixer. – pro Oct 28 '16 at 2:53

When you exchanged, did the problem occur in the shop? Why don't you take this back as well? Have you tried connecting using the XLR? Is the phantom power turned off? Does it happen when it's used as a monitor with other equipment? Does it happen when it's used as a mixer amp in its own right, or just when it's a monitor?

All these need addressing. They may sound like questions (they are!), but they may give the answer too.

  • Is it the same sort of 'thump' you'd get from pulling the cable out? – Laurence Payne Nov 26 '16 at 13:40

The problem was that the spring in the quarter-inch cable socket was extremely stiff and so the jack wasn't fully engaged. When I applied much more pressure to inserting the jack, it fully engaged. The spring is now less stiff and so now normal pressure can be used to engage the plug.

  • Note that I've never seen a 1/4" jack where you can see any of the sleeve after the plug is fully inserted, so that's one way to have a sense of whether a cable is all the way home or not. I'm glad someone noticed this in your case. New equipment does sometimes have overly tight sockets. – Todd Wilcox Jan 16 '17 at 9:50
  • It's a Neutrik jack. The amount of space showing was so small it was easy to miss. – pro Jan 16 '17 at 18:38

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