Please help with hum in IB with BFD

**howburger** · **05-17-06, 10:02 PM**

I've got an IB sub with BFD and EP2500. I've got a nasty hum/buzz coming through my sub drivers that I have traced to the interconnect coming from the sub out on my Rotel processor. Of course the I/C goes to the BFD. When I remove the I/C from the processor, the hum goes away. I've tried plugging all associated equipment into the same outlet to avoid ground loop problems, to no avail. The I/C is a cheapish Monster sub cable. Could a highly shielded DIY I/C cable possibly eliminate this? Or is there such thing as a cable with RCA on one end to the processor and balanced at the other end to the BFD, and if so, could that help? Please help, I'm frustrated and lost.

Thanx,

Harold

**brucek** · **05-17-06, 10:11 PM**

Give this section in the BFD Guide a read..

**Sonnie** · **05-17-06, 10:23 PM**

Check out this post ... it might help. These are about the only solutions we've been able to come up with.

EDIT: lol... I musta sit on this for a few minutes before I hit submit... I didn't even notice brucek's post, but both places say pretty much the same thing so you are good to go.

**Phil M** · **05-18-06, 07:42 AM**

I had the same problem - I tried using a different interconnect and this did not solve the issue. Next I tried an in-line filter on the interconnect, also didn't work.
The cheater plug did - but this was used as a temporary solution, and I ultimately fixed it by rerouting my Rotel 1098.
I would try the cheater plug first - under the safety caveat - just to isolate the source and type of problem.

NB
As an aside it might be coincidence but only Rotel products gave me this problem, they may more susceptible to picking up ground loops.

**Josuah** · **05-18-06, 12:23 PM**

I've used XLR interconnects, with XLR ground lift adapters, to deal with my hum/noise problem. This worked even though the noise was there when all of my equipment was plugged into the same outlet (all equipment being everything unplugged except the processor and amp).

Since getting an FBQ2496, I also placed an XLR ground lift adapter on that input. The FBQ2496 introduced a tiny bit of noise/hum. It's also on the same circuit as my pre-pro and amp.

**howburger** · **05-18-06, 04:57 PM**

I've tried the cheater plug, did not work. I may try the DCI Hum Eliminator to see if it works. Very frustrating, I just quieted my EP2500 with a Panaflo fan and the hum is the only unwanted noise left in my theater. I have an electrician coming this weekend to pull two dedicated 20 amp circuits to my room, maybe that will even work. I'll post when I have the problem solved.

Thanx guys,

Harold

**Josuah** · **05-18-06, 05:50 PM**

Actually, in my particular case it was not a ground loop hum. So a 3-prong to 2-prong cheater plug wouldn't work. My pre-pro and amp are both 2-prong anyway.

The only thing that worked was switching from RCA to XLR and inserting XLR ground lift adapters on specific channels. Not all of them, otherwise there is no ground between the pre-pro and amp and thus no way to "zero" the signal. When I did try this, the noise floor went way up. I think using something like the Hum Eliminator with unbalanced signals would not have solved my problem, but just shoved the noise floor way up.

**howburger** · **05-19-06, 01:47 AM**

I googled "hum and BFD" and came across the link below. I'm going to try a short length of RCA cable between the BFD and EP2500 with the shield connection snipped and see if that works. I will let you know how it goes.

http://www.users.bigpond.com/bcolliso/earth-loop.htm

Harold

**brucek** · **05-19-06, 07:46 AM**

Quote:

I'm going to try a short length of RCA cable between the BFD and EP2500 with the shield connection snipped and see if that works

An unrecommended solution.

Also note that many interrconnects use 'paired cable' within the coaxial shield to supply the complete signal path with one end of the shield opened. Don't use one of these for your experiment.

The EP2500 uses balanced connections only I believe. Have you lifted the shield on the XLR between the BFD and EP2500? This would be be an acceptable solution if it worked.

When you tried the cheater, did you test it on the EP2500 or just the BFD?

brucek

**howburger** · **05-19-06, 09:23 PM**

I'm embarrassed.

All this time I thought I had ruled out the cheater plug as the problem. In my doing so, I had tried it on the BFD and the EP2500, but not at the same time. Today I went back and put one on each and the hum was gone. What a relief!

Thanx guys,

Harold

**Sonnie** · **05-19-06, 11:40 PM**

No reason to be embarassed howie... you have created a great thread for others who might run into the same problem, and believe me, it will happen to someone else sooner or later and they will be glad you were the ... uh.. er... you know.

**howburger** · **05-20-06, 12:03 AM**

Thank you guys. It's great to have an on-demand support team to rely on.

Harold

**Phil M** · **05-20-06, 09:18 AM**

At least you know what the problem is now Howie, I used the cheater plug for about a year and then switched interconnects and outlets around - the hum disappeared.
Most sources are found to be cable boxes - I switched to satellite, maybe that was the source. Worth taking a look?

**crutschow** · **10-18-06, 11:55 PM**

Comment about using an XLR ground lift: For an unbalanced (single-ended) connection to the BFD input, an XLR ground lift adapter removes the ground connection to the chassis/ground pin on the balanced input connector and breaks the ground loop. This leaves the signal connected to the hot(+ve) input and the ground (common of the signal source) connected to the cold(-ve) input. This creates an unbalanced input signal to the balanced inputs, but that should work since the BFD likely responds to the difference between the hot and cold signals (which is the desired signal) and rejects the voltage common to both signals (which is the hum voltage difference between the two chassis). (Caution: Use a ground lift adapter only if both units are connected with a grounded AC plug, preferably to the same outlet, otherwise unsafe voltages could develop causing possible injury or equipment damage)

**Josuah** · **10-19-06, 11:19 PM**

Yeah, don't leave the cheater plugs. You're setting yourself up for hurting yourself or your stuff if you do.

**GaryK** · **11-26-07, 05:00 PM**

Not sure where I found this solution for the BFD hum, but it worked great for me and it won't get you electrocuted

Add 4 narrow filters to your program as listed below.
Filter 9: ON PA Fc 1,000.0Hz Gain -48.0dB BW/60 10.0
Filter 10: ON PA Fc 1,250.0Hz Gain -48.0dB BW/60 10.0
Filter 11: ON PA Fc 1,620.0Hz Gain -48.0dB BW/60 10.0
Filter 12: ON PA Fc 2,000.0Hz Gain -48.0dB BW/60 10.0
As always, your mileage may vary....

**brucek** · **11-26-07, 05:27 PM**

Mmm, can't see why that would help. Those frequencies aren't usually associated with the range that would be considered hum from a ground loop....

brucek

**GaryK** · **11-27-07, 09:51 AM**

I am afraid that I have forgotten the theory behind it, but I yesterday I added another Program (I was trying out Wayne's "knee" curve which worked great BTW) and had the horrible hum. I dug thru some old paper print outs and found this cure and once again it worked for me.

**tweakophyte** · **11-28-07, 07:13 AM**

I've had sucess with my ART cleanbox II. I tried it in a few spots in the connection chain. Adding it between the receiver and the BFD is what worked. You can get them for around $35 if you shop and/or negotiate.

**lovingdvd** · **12-01-07, 11:49 PM**

Quote:

crutschow wrote:

...Caution: Use a ground lift adapter only if both units are connected with a grounded AC plug, preferably to the same outlet, otherwise unsafe voltages could develop causing possible injury or equipment damage

Can you please elaborate on this some more? My AVR uses only 2 prong AC plug. This feeds my BFD via a custom XLR cable I made that lifts the ground, which I understood to be safe as opposed to using a cheater plug (which would have been far easier). The BFD is a 3 prong AC, the sub is 2 prong.

Are you saying then that in the above scenario I should not be using my custom XLR cable that lifts the ground? This is not safe? I ask because my sub's internal amp crapped out on me recently. Turned out the controller board in the amp went bad. I suspect it may have been the result of some intermittent power issues in the neighborhood, despite the sub and BFD being plugged into an APCC battery back up with surge protection.. ?

**brucek** · **12-02-07, 07:55 AM**

Quote:

Are you saying then that in the above scenario I should not be using my custom XLR cable that lifts the ground? This is not safe?

It is perfectly safe. The BFD has a three prong plug. The shield that you are lifting is simply blocking any signal that may be present on the shield.

A two prong device doesn't require the safety ground since the circuitry is isolated from its exterior.

The cable has nothing to do with your sub malfunction.

brucek

**toecheese** · **12-03-07, 11:09 AM**

I got a weird ground hum- I had eliminated others by going to optical connections on some components.

But if I plug my cable wire into my HDTV tuner (instead of the antenna), it returns.

**lovingdvd** · **12-03-07, 02:47 PM**

Quote:

toecheese wrote:

I got a weird ground hum- I had eliminated others by going to optical connections on some components.

But if I plug my cable wire into my HDTV tuner (instead of the antenna), it returns.

Have you gone through this thread: http://www.hometheatershack.com/foru...d-bfd-hum.html in detail?

**toecheese** · **12-04-07, 12:18 PM**

No- should this thread be locked and everyone go there instead?

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