Yet another BFD hum post

[grn1969c10]

I didn't have proper cabling for the BFD, so I made some up from old parts. The connection from amp to BFD is constructed as per #17 in Rane's system interconnect guide displayed in post #2 of mississippi-xj's BFD hum thread. The connection from BFD to sub is a 1/4" stereo jack to rca plug. I tried it with the sleeve open and then I tried the sleeve shorted to the ring.

The BFD has a very slight hum with no connections that can be heard when you are within a foot or two of it. Not enough to bother me. When connections are made and the sub turned on, the sub hum is definitely noticeable and annoying. Powering on the receiver causes the sub hum to increase to a room filling loud buzzing.

Usually ground loops are investigated first. Rane #17 has the ground lifted at the unbalanced end. I tried the connection to sub with the sleeve open. Both sub and BFD are on cheater plugs and the receiver has 2 prong power plug. Receiver powered on amplifies the buzz considerably.

Any ideas?

[Wayne A. Pflughaupt]

Make sure the shield is truly lifted at the RCA end. This can be a bit tricky to accomplish. If any piece of the shield touches the RCA's arm/clamp assembly, you have a connection. This post will show you how to make sure your connection is correct.

If your cable is correct, then disconnect the cable TV connection from your system and see if that makes the noise go away.

Regards,
Wayne

[grn1969c10]

Thanks Wayne,
That is a right nifty soldering tutorial.

I made a trip and picked up two 1/4" mono to RCA jack adapters and used standard sub cables to hook up the BFD and sub. The hum has mostly disappeared. I still have a two foot cable that is completely unshielded which is letting noise into the system. I think it's bearable until I can get two more adapters. I still have to use the cheater plugs on the power cords. You would think that with everything plugged into a single Furman power strip that ground loops wouldn't occur...

[texfrazer]

If you're still having to use cheater plugs, it seems like there is something other than your 2 foot unshielded cable letting in noise. Try disconnecting the cable like Wayne suggested and see if you still need the cheater plugs. Cable and satellite connections are notorius for not being properly grounded.

Keep us updated on your progress!

[grn1969c10]

The noise without cheater plugs is a very load buzz. One of those turn-it-off-quick sounds! Everything (including tv cable) is plugged into a single Furman PST-8D powerstrip/conditioner which is plugged into a grounded receptacle. I don't understand how the different pieces of equipment can have different ground potentials. I guess I could try bonding the BFD and receiver cases together.

The reason I bought the Furman, is my DVD player occasionally skips when I open the microwave door, turn on the stove, turn off lights, ceiling fans, etc. These are on competely different branch circuits in different rooms. Talk about annoying. All this work to make the sound system sound halfway decent and then in the middle of the movie the sound drops out for a second before resuming. Come to think about it, I'm not sure I have ever noticed a problem with the picture, only the sound. But maybe old analog tvs are more tolerant of a brief glitch in the input signal.

The "little" buzz I mentioned only occured when I used a 2' jerry-rigged cable made from speaker wire to hook up another sub.

[Wayne A. Pflughaupt]

Everything (including tv cable) is plugged into a single Furman PST-8D powerstrip/conditioner which is plugged into a grounded receptacle. I don't understand how the different pieces of equipment can have different ground potentials.

That could easily come from the satellite or cable TV coaxial feed, especially if they are grounded somewhere other than your electrical ground stake.

Regards,
Wayne

[grn1969c10]

the satellite or cable TV coaxial feed

I will have to email furman and find out if the PST-8D provides any isolation for the cable. I also want to ask them about the DVD interference. I was cooking yesterday (don't do that often!) and the thing skipped constantly. I think it skipped every time the stove burner cycled on or off. I had to turn the music off until the bacon was done.

Speaking of bacon...

Happy Thanksgiving Everybody!