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Author Topic: Wicked buzz from my Powered Mackie Thump 15-A's  (Read 5899 times)

randtor

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Wicked buzz from my Powered Mackie Thump 15-A's
« on: May 17, 2011, 06:16:16 pm »

Hey all,
I've read lots of posts on Vdrum forums concerning ground loops and such. I have a Roland TD-10 into the TH-15's, and when I turn the volume up on the Thumps I hear a definite buzz, like a ground loop. If I turn the Thump volume down and the Roland module way up, I have less hum, but it is still there. I have plugged and unplugged different components, one at a time, and get no change (wireless, direct box, hum debugger). I have also tried a Roland TD-20 as well, with no better results. So, I have eliminated the Roland module, the wireless receiver and transmitter in the Zendrum (Shutting off the Zendrum makes no difference), the direct box, and even tried a Hum Debugger. I hear the buzz from the speakers no matter where the speaker is plugged in.... at home, at a gig, etc. I have tried plugging the speaker into a different outlet than the rest of my components, but no change there either.
I have a powered strip that cost a LOT of $$$ to try and wash the electrical power so it's clean..... no joy. I still hear the buzz,which does go away only when I unplug the cord from the back of the speaker. I have tried a {1/4" /  XLR} wire from the Roland, to the back of the Thump; I have also tried 1/4" from the Roland module to a direct box, and thence one of 2 set ups to the Thumps....(a) 1/4" out from direct box to XLR in Thump, or (b) XLR out from direct box to XLR in Thump). When there is no signal in to the Thump the buzz stops, even with the speaker volume all the way up. I'm no electronic wizard, but it seems to me that it has to be the line IN, and NOT the speaker. Trouble is, how do I find out the problem, and how do I fix it? I think I've tried eliminating every component, and all the cords are new and of excellent quality.
Any thoughts or suggestions are appreciated. Thanks!

Rand
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THUMPER

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Re: Wicked buzz from my Powered Mackie Thump 15-A's
« Reply #1 on: May 17, 2011, 08:16:34 pm »

Im sure you thought of this already but make sure the thumps,roland,zendrum are all plugged into the same circuit/outlet. Thumper
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randtor

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Re: Wicked buzz from my Powered Mackie Thump 15-A's
« Reply #2 on: May 18, 2011, 11:13:30 am »


Thanks Thumper,
Yeah man, I tried separate circuits, all in the same circuit, with and without an extension cord. Nada.
Is it possible there is some sort of cheap or lousy component in the Thumps themselves, that is allowing this buzz to occur?
After all, I have eliminated any other component. When nothing is plugged in to the XLR, all I hear is a slight normal speaker hiss with the volume all the way up. With the cord attached, I get buzz until I turn the volume down to about 60%.
Rand
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DrumWagon

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Re: Wicked buzz from my Powered Mackie Thump 15-A's
« Reply #3 on: May 18, 2011, 11:52:04 am »

Sounds like a classic ground loop problem.  Do your DIs have a ground lift feature?  I presume you've messed with all the settings there.

One trick I've had luck with (in a studio environment) is to clip the ground connection on ONE end of the XLR cables.  This breaks the ground loop while still allowing the shielding to function as an EM filter.

Another fix would be to pick up some audio isolation transformers, though the better ones can be expensive.

With my laptop rig, I was able to solve a nasty hum problem by clipping off the ground pin of the power brick.  Definitely not recommended for most circumstances,  but worked like a charm and since the brick is encased in plastic and is tucked away where I never touch it, is a reasonably safe solution.

There's tons of info online about ground loops, but here are some links to get you started from a site I found to be helpful:

http://www.epanorama.net/documents/groundloop/groundlift.html
http://www.epanorama.net/documents/groundloop/problem_solving.html
http://www.epanorama.net/documents/groundloop/audio_isolators.html

HTH
« Last Edit: June 02, 2011, 12:45:18 pm by DrumWagon »
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Re: Wicked buzz from my Powered Mackie Thump 15-A's
« Reply #4 on: May 18, 2011, 01:28:50 pm »

Just had another thought, when my mackie 450 introduuced a hum it was when I had the switch on mic input and not on line input
Thumper
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randtor

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Re: Wicked buzz from my Powered Mackie Thump 15-A's
« Reply #5 on: May 18, 2011, 08:33:03 pm »

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!
Cheers,
Rand

PS:
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!
« Last Edit: May 18, 2011, 08:39:54 pm by randtor »
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DrumWagon

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Re: Wicked buzz from my Powered Mackie Thump 15-A's
« Reply #6 on: May 18, 2011, 09:22:40 pm »

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.

HTH
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randtor

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Re: Wicked buzz from my Powered Mackie Thump 15-A's
« Reply #7 on: May 18, 2011, 10:17:26 pm »

Darin,
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!

Rand
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Re: Wicked buzz from my Powered Mackie Thump 15-A's
« Reply #8 on: May 18, 2011, 10:38:20 pm »

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

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Re: Wicked buzz from my Powered Mackie Thump 15-A's
« Reply #9 on: May 18, 2011, 10:53:16 pm »

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?
Thanks,
Rand
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randtor

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Re: Wicked buzz from my Powered Mackie Thump 15-A's
« Reply #10 on: May 18, 2011, 10:59:47 pm »

Aha! I just found this : http://www.cablestogo.com/product.asp?cat%5Fid=2029&sku=40037

They have a 25' xlr to male mono cable, $36.99. I'd rather have one cable , than have a connection between 2 cables. 2 interconnected cables just seems to me to be an invitation to trouble.  ::)

Thanks guys, looks like I should have this under control now. It was frankly embarrassing at our last gig, a private party, when between songs, you could hear my speakers buzzing almost as loud as the fluorescent light fixtures!
Rand
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Re: Wicked buzz from my Powered Mackie Thump 15-A's
« Reply #11 on: May 19, 2011, 08:51:31 am »

I have the shorter cables as I had been putting the mackies just behind me and the TD-20. If I needed to then I took the other xlr out of the speaker to xlr (regular mi cable) to the PA. I have also used a splitter cable from the TD-20 so one would got to the board and one woud go to the mackies. There are different ways to go on this you just have to find the one that works best for you. I think as a rule of thumb less connections equal better sound. Good luck Thumper
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randtor

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Re: Wicked buzz from my Powered Mackie Thump 15-A's
« Reply #12 on: May 19, 2011, 06:24:48 pm »

Thanks Thumper,
I ordered the 25' cables last night; I generally try to get as much space between the speakers as possible to enhance the stereo sound.
So, I CAN run the xlr from the back of the speaker to the PA board or mixer then, as you said. Thats great news. Now I have several choices. I like using the Direct box, it's pretty convenient and is an easy way to send signal to the speakers and the board.

You have to love this forum, eh?!?! I have been stumped several times, and I always seem to get an answer here. And strangely, most of the time it's the right answer!  ;D  I LOVE my zendrum!!

Rand
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DrumWagon

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Re: Wicked buzz from my Powered Mackie Thump 15-A's
« Reply #13 on: June 01, 2011, 05:42:37 pm »

Actually, most all Roland units (including the TD-10) have unbalanced outputs (don't get me started on what they were thinking! :-\ )

When using a Roland unit, I would recommend going immediately into a DI, assuming the rest of your audio chain is balanced.
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Re: Wicked buzz from my Powered Mackie Thump 15-A's
« Reply #14 on: June 02, 2011, 12:18:31 pm »

D-Wag,

Geez, you're right!  I deleted my post from earlier as the whole darn thing was based on my misinformation about the outputs.

Why oh why would they not have balanced outs?!?!?!??

Sorry Rand et al, I shoulda done more research first...!

Jer
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