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Wicked buzz from my Powered Mackie Thump 15-A's

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Ummmm, I think I found the problem. See if you all agree?

I was using a 25 foot 1/4" to XLR cable from the back of the Roland directly into the Thump. As mentioned, I tried going from the Roland to a direct box with a 1/4 cable on both ends; then out from the direct box "thru"-1/4 fitting, to the XLR connection in the Mackie Thump, with a cable that had the 1/4 on one end and the XLR on the other. Still buzzing. So for grins, I hooked an XLR to XLR cable from the Direct Box Low-Z out, to the Mackie Thump, keeping the 1/4 plug going from the Roland to the Direct box and eliminating the "thru" connection from the direct box to the Thunp, (1/4 to xlr). NO BUZZ.
There is a definite loss of signal strength, ie: everything is coming through quieter, but I can raise the volume of the Thump to FULL, with no buzz, and I can raise the volume of the Roland Module to full, and still no buzz. But there is a definite loss of overall volume, I think because I am not using the direct box properly. Hmmmm. As I understand the Direct box, the IN and THRU are supposed to be used as I was, going from the Roland module to the IN, then from the THRU to the speaker. The Low-Z outs are supposed to carry a signal to a mixer, I suppose to use a FOH PA system, or for recording purposes. Still, I have no buzz. Now...........

In looking over the cords, I suddenly realized that the 25' 1/4" to XLR could be the problem. The 1/4" plug is STEREO! Not mono. Could this be the cause of my buzz? I'm thinking I have a stereo plug, so 2 wires are involved, yet I'm using it in a mono imput in the roland. Perhaps this is creating my ground loop?

Tomorrow I am going to get a 1/4" MONO to XLR adaptor, attach it to my XLR to XLR cord, go from the back of the Roland (1/4") to the speaker directly (XLR) and see if my buzz is still gone. I'm thinking it will be .... well, I'm hoping it will be!

Update tomorrow!

Darin, I was checking out your links when I tried this other setup after reading a bit on the first link. That prompted me to try it this way. Thanks for the other thoughts as well, I may try clipping the xlr wire connectors if this doesn't work.
Thumper, I don't have the input switches on the Mackie that you mentioned, but thanks for the thoughts!

So yes, you were essentially using a 25' unbalanced cable.  That's an open invitation to every buzz gremlin in the joint to hop on-board.   ;)  You definately want to keep any unbalanced lines as short as possible.  With my Roland setup, I only have a 1 foot line from it that goes straight to a DI, with everything being balanced from that point on.  AFAIK all Roland sound modules are unbalanced, so it's a necessary evil.

Sounds like you've got a handle on it now though.  The loss in signal strength is likely due to attenuation being applied by the DI.  Most units allow you to adjust this though, usually by selecting a preset range (+/- 0, 20 or 40db for example).  Some units also allow you to match the impedance too as the line levels for say a drum module are different than say a guitar or a microphone.  Typical selections there are 2.2, 22 and 400K.


Yes, from the Roland to the Direct box, 1/4" mono on both sides of the cable, I keep it short, my cables are 3 feet.

The problem now becomes going from the Direct box to the speaker, since it needs to be 1/4 mono from the box, and xlr male to the speaker. I cannot locate a cable like that! So, I guess the next best solution is to get an adaptor to convert one end of the xlr/xlr cable to a 1/4 mono plug. At that point I don't think the cable would still be considered a 'balanced' line though, since it goes from 3 wire at the xlr to 2 wire at the 1/4 ts plug, right? The only other solution is to continue running out of the direct box as I am, using the Low-z out xlr connection, so I can continue to use the xlr/xlr cable.

That now presents another problem, lol! How to then run sound to the mixer, if I am using those outs from the direct box. The Thumps actually have an xlr female out connection to daisy chain speakers if I want. Can I use those with an xlr to the board, and get the sound there for recording purposes, or FOH PA use?

Darin, you are a big help! When I read this back, it seems pretty confusing, and yet you are able to interpret it all!
I very much appreciate your help as always!!

Oh, btw, you are correct, there was a button on the direct box, called a PAD, for -15dB, I assume that what was causing my signal attenuation. When I pushed it in and it released, I suddenly had my volume back. Terrific!!
Thanks again. I am on the hunt for a cable that has 1/4" mono and XLR male ends!


 I bought 1/4" mono to male XLR at guitar center Thumper

Just what I was looking at, Guitar Center.
They have this: "Monster Cable 1/4" Male Mono to 1/4" Female Stereo Cable Adapter", which is what I need. I have 25' cables that are xlr male on one end (to the speaker), and 1/4" male stereo on the other end, causing my problem. So I can plug the stereo 1/4" into the female 1/4" of this new little cable, then the other end of this cable has the 1/4" male plug, which will go into the direct box. That should solve my problem I hope. These little cable (6"!) are not cheap however... $19.95 each!
The only other choice is this: "Rapco Horizon Hi-Z 1/4" Male-XLR Male Cable", but those are also $20, and are only 15 feet. I don't see any 25-30 foot cables with the xlr male and 1/4 male mono ends. Do you have that?


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