What solution do folks use for the dreaded BFD hum? - Page 22 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #211 of 330 Old 08-25-09, 06:02 PM
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Re: What solution do folks use for the dreaded BFD hum?


Quote:
brucek wrote: View Post
Quote:
ran some #10AWG solid copper ground wire from the ground rod
Not large enough. Should be #6 or better.
#6 between the coax cable ground block and ground rod? Are you sure? Seems like mundo overkill...

Quote:
waldo563 wrote: View Post
However, my BFD is still connected using 1/4" mono to RCA adapters and I would like to build some more permanent XLR to RCA cables with the shield attached at the XLR end as suggested by Wayne.

My question is, do these modified cables go between the AVR and the BFD input only and "standard" XLR to RCA cables with the shield connected on both ends and pins 1 and 3 shorted used between the BFD output and the sub? Or would it be better to use the modified cables at both ends.
Connect the center conductor to Pin 2, and the shield to Pin 3. Don’t jump between pins 1-3. I made both my in and out cables this way, just seemed like the thing to do since I was taking the trouble to custom-making them anyway. But as brucek says, lifting the shield on the input should suffice.

Regards,
Wayne



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post #212 of 330 Old 08-25-09, 06:04 PM
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Re: What solution do folks use for the dreaded BFD hum?

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lcaillo wrote: View Post
This is a very common scenario. I strongly suggest that grounds be checked regularly. One should be careful. If there is a problem with the neutral, an open ground cound be a hazard. Not likely, but if things are loose and you fiddle, there could be danger. Best to maintain a ground connection with a second clamp while working on the first if possible if working on the electrical service ground. Not much danger if just working with a cable, sat, or phone ground.

I just did a service call this morning that had a bar rolling through the pix and it was a bad ground on the cable installation.
I recently did some work in an apartment complex, DirecTV and Dish dishes everywhere. None of them grounded to anything...

Regards,
Wayne



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post #213 of 330 Old 08-26-09, 01:29 AM
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Re: What solution do folks use for the dreaded BFD hum?

Quote:
Wayne A. Pflughaupt wrote: View Post

#6 between the coax cable ground block and ground rod? Are you sure? Seems like mundo overkill...


Connect the center conductor to Pin 2, and the shield to Pin 3. Donít jump between pins 1-3. I made both my in and out cables this way, just seemed like the thing to do since I was taking the trouble to custom-making them anyway. But as brucek says, lifting the shield on the input should suffice.

Regards,
Wayne
The #6AWG stranded copper is between the cable ground rod and some electrical conduit going to the AC switch box. I believe #6AWG or larger is required by the National Electric Code when grounding a dedicated satellite/cable ground rod to the structure ground when connection to the structure ground rod is not feasible. I used #10AWG solid copper to go from the ground rod to the coax cable ground block.

Regarding the XLR/RCA cables, I ended up taking the lazy way out and ordered some cables from Monoprice. It appears that the hum/buzz problem was related to my Onkyo TX-SR606 AVR with HDMI inputs - a problem which seems pretty well documented for that model. I took the BFD out of the signal chain and still had the hum so, not wanting to deal with it anymore, I replaced it with a Denon AVR-1910 and it has not manifested again although I have only had it for a couple of days. So I'm counting on the Monoprice cables working as is but, if not, then I hope they can be modified without too much effort.
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post #214 of 330 Old 10-01-09, 08:17 AM
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Re: What solution do folks use for the dreaded BFD hum?

To check for ground loops other than by guessing and trial and error, you could spend $20 - $30 for a multimeter. Go to the Mouser web site and check catalog page 2092 (I don't have enough posts yet to post URLs). There is the B&K 117B analog and 2405A digital.

A ground loop will show up as a voltage between two ground connections which you can measure using the volt meter part of your multimeter. After you've solved your ground loop problems you can use it as a battery and outlet tester.
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post #215 of 330 Old 11-15-09, 11:12 PM
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Re: What solution do folks use for the dreaded BFD hum?

I just wanted to reiterate what others have said about fixing my ground loop. After putting in my BFD, I had the hum/ground loop between the BFD and my (two-pronged) AVR. After trying some other things (including a cheater plug, which worked but I didn't want to gamble with), I went back and re-read some of the posts in here. I was able to modify my RCA-XLR cable to go from shield--pin 3 instead of shield--pin 1, which eliminated the hum.

Thank you all for the great info in here, and Wayne in particular for the instructions on the cable!
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post #216 of 330 Old 11-27-09, 12:39 PM
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Re: What solution do folks use for the dreaded BFD hum?

Like many here, but trying to eliminate the BFD hum. Cheater plug fixes it, but I know that's not a permanent solution.

I see in this post a recommended way to fix the hum... it appears this method works for many people - is this the best/easiest way?

Looking at buying the components, I found:
CablesToGo XLR to RCA cables... anybody test these to know if they are wired this way already?

Assuming they are not, it appears one way is to make your own buying something like http://www.amazon.com/Cables-Go-40058-Pro-Audio-Female/dp/B0002J2NXQ/ref=sr_1_6?ie=UTF8&s=electronics&qid=1259345614&sr=8-6 - cut them in half, and solder on http://www.amazon.com/Atlona-RCA-Connector-Red-Color/dp/B002OB9Y1E/ref=sr_1_23?ie=UTF8&s=electronics&qid=1259346873&sr=1-23
Has anybody found a supplier that makes these cables already? I don't mind making them, but I also don't mind paying someone to avoid having to put it together myself if I know it works

< edit: ugh, nice Amazon logos... sorry >
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post #217 of 330 Old 11-27-09, 01:25 PM
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Re: What solution do folks use for the dreaded BFD hum?


I expect that any over-the-counter RCA to XLR cables is going to combine the shield and signal (-) at the RCA end. The DIY method you're contemplating is the best remedy.

Regards,
Wayne



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post #218 of 330 Old 11-28-09, 01:36 PM
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Re: What solution do folks use for the dreaded BFD hum?

thanks Wayne. I contacted BlueJeans yesterday and they said they'd make this cable for the same price as their normal XLR to RCA - just fill out the custom cable form.
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post #219 of 330 Old 12-05-09, 02:11 PM
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Re: What solution do folks use for the dreaded BFD hum?

I am buying RCA to XLR cables from monoprice; what would be the easiest way to convert them to pseudobalanced cables to rid my system of hum when using the BFD in my system. I get a hum when the current RCA to TS cable is connected from my receiver to the BFD-- no hum if I disconnect the that cable but leave the BFD to Subwoofer cable connected.
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post #220 of 330 Old 12-19-09, 03:50 PM
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Re: What solution do folks use for the dreaded BFD hum?

I finished building my custom cables - worked perfectly - no more hum!

I followed this post - except I used XLR connectors to RCA. Basically the same as this post but without tying it to ground (just cut the end of the shield wire).

Bought a simple XLR to XLR cable and Dayton RCA connectors. Cut XLR cable in half and soldered on the RCA end. Took me all of about 20 minutes to make No more hum
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