What solution do folks use for the dreaded BFD hum? - Page 24 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #231 of 330 Old 03-20-10, 09:42 PM
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Re: What solution do folks use for the dreaded BFD hum?

I've got the ground loop hum out of my sub now that I have a BFD. If I remove both the HDMI cable out to the TV and the HDMI cable that goes to my Directv box, the hum goes away. I have to have both disconnected to get rid of it. I only have to plug one of them back in to get the hum again. I checked out my sat install and it looks like it is properly grounded. In this case, how can I identify where the ground loop is? Note that I have the BFD and the sub plugged in outlets different than the receiver since they are on opposite sides of the room. I don't know if this is an issue.
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post #232 of 330 Old 03-21-10, 07:21 AM
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Re: What solution do folks use for the dreaded BFD hum?

That makes sense since your TV and DirecTV box are tied together also so leaving either one connected will give you the hum.

Having them on different potential electrical circuits isn't helping anything though my first guess would be a poor ground of the satellite system. That's not at all uncommon.

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post #233 of 330 Old 03-21-10, 10:44 AM
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Re: What solution do folks use for the dreaded BFD hum?

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bpape wrote: View Post
That makes sense since your TV and DirecTV box are tied together also so leaving either one connected will give you the hum.
This is why I'm confused. Once I disconnect the HDMI cable from the DirecTV box to the receiver, the box isn't connected to anything anymore. This means it is not the sat ground that is the problem. I just verified this by disconnecting the sat coax and the hum is not affected. Also, both the mast and the coax appear to be grounded properly at the same place as my main electrical panel.

Quote:
Having them on different potential electrical circuits isn't helping anything
I guess my only solutions are to build a custom cable or buy a transformer.
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post #234 of 330 Old 03-21-10, 02:47 PM
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Re: What solution do folks use for the dreaded BFD hum?

I made a rca to xlr cable as described in this thread and that took care of the hum. I still have a very low hiss that is inaudible unless you're really close to the sub. This will work for now, but I think I'm going to get a Jensen sub-1rr.
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post #235 of 330 Old 03-21-10, 05:12 PM
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Re: What solution do folks use for the dreaded BFD hum?

OK. Is anything else hooked up to the TV like a VCR, cable box, etc? Just looking for another ground path.

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post #236 of 330 Old 05-28-10, 11:47 AM
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Re: What solution do folks use for the dreaded BFD hum?

Obviously, this is a long thread, with lots of possible solutions to lots of different problems with the same symptom--BFD hum. I just wanted to thank everyone for the great info here, and possibly add to the collective knowledge about this issue by noting the specific solutions which worked for me.

I've got a Denon AVR connected via HDMI to a cable box, HTPC, and an Epson projector, and via the RCA sub out jack to a BFD, which then goes to a Behringer EP2500 to drive the subs. By disconnecting everything, then adding components one at a time, I was able to determine that I had a ground loop through the projector. I temporarily ran the projector on an extension cord back to the same surge suppressor where everything else is plugged in, and *most* of the hum disappeared. Fortunately, I don't have the drywall finished in the theater room yet, so I still have the option to wire the outlets so that this fix becomes permanent.

The remaining hum was present whenever the BFD & sub amp were connected to the receiver, even if nothing else was plugged into the receiver. I was previously using an RCA-to-XLR cable (from Markertek, I think), and when I opened up the connector at the XLR end, I saw that pins 1 and 3 were bridged together. This is the configuration recommended in the BFD manual for unbalanced-to-balanced connection, but it's not the same as what BruceK proposed here.

Since I had a spare TRS-to-TRS cable, I cut an end off and soldered up an RCA connector exactly as shown in BruceK's post--no connection to the shield at the RCA end. I just tested it, and I'm pleased to report that it worked perfectly! There is absolutely no more hum, even with the amp at full gain. Thanks everyone, and especially BruceK!


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post #237 of 330 Old 05-28-10, 04:09 PM
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Re: What solution do folks use for the dreaded BFD hum?

Quote:
CraigG wrote: View Post
Obviously, this is a long thread, with lots of possible solutions to lots of different problems with the same symptom--BFD hum. I just wanted to thank everyone for the great info here, and possibly add to the collective knowledge about this issue by noting the specific solutions which worked for me.

I've got a Denon AVR connected via HDMI to a cable box, HTPC, and an Epson projector, and via the RCA sub out jack to a BFD, which then goes to a Behringer EP2500 to drive the subs. By disconnecting everything, then adding components one at a time, I was able to determine that I had a ground loop through the projector. I temporarily ran the projector on an extension cord back to the same surge suppressor where everything else is plugged in, and *most* of the hum disappeared. Fortunately, I don't have the drywall finished in the theater room yet, so I still have the option to wire the outlets so that this fix becomes permanent.

The remaining hum was present whenever the BFD & sub amp were connected to the receiver, even if nothing else was plugged into the receiver. I was previously using an RCA-to-XLR cable (from Markertek, I think), and when I opened up the connector at the XLR end, I saw that pins 1 and 3 were bridged together. This is the configuration recommended in the BFD manual for unbalanced-to-balanced connection, but it's not the same as what BruceK proposed here.

Since I had a spare TRS-to-TRS cable, I cut an end off and soldered up an RCA connector exactly as shown in BruceK's post--no connection to the shield at the RCA end. I just tested it, and I'm pleased to report that it worked perfectly! There is absolutely no more hum, even with the amp at full gain. Thanks everyone, and especially BruceK!

I go this route, it allows me to ground at the AVR and complete the shield end to end:




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post #238 of 330 Old 05-28-10, 04:52 PM
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Re: What solution do folks use for the dreaded BFD hum?


Not sure how that would do anything to help a ground loop? The barrel (sleeve) of the RCA jacks have continuity with the chassis of the AVR. IOW, itís functionally the same as the black wire and shield being tied together.

Regards,
Wayne



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post #239 of 330 Old 06-09-10, 05:09 PM
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Re: What solution do folks use for the dreaded BFD hum?

Run your whole sound syetem + TV and everything else that is connected to your system on one or if needed two dedicated circuits on a 20 a breaker and don't hook up anything else to it, that is relatively easy if you have room for one or two more breakers in your breaker panel,the cables don't have to run inside the walls, that doesn't look to pretty,but may be try it , that worked in my case.
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post #240 of 330 Old 06-13-10, 10:59 AM
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Re: What solution do folks use for the dreaded BFD hum?

Ive had a BFD in my system for about 6-7 months now with no problems....until recently. I have a popcorn hour A-200 which was in the system for about 2 months with no problems. I changed the casing on the PCH to a 3rd party metal casing as the original plastic one was terrible and had a fan inside it which was noisy. Anyway, changed the casing and put back into my system. It connects via HDMI to a pioneer AVR.

A few weeks ago I had to do a strip down of the system and upon reconnecting everything up I know can hear the PCH through my sub In fact when it boots up I can hear the hard drive in it taking off. I dont understand how this can happen when it wasnt there before. Ive tried changing cables round etc but no luck. Ive had to disconnect BFD and connect Sub direct to AVR. Any ideas?
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