ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi BeoWorld Forum member,
I figured I would ask my question here since many of you own B&O speakers or systems.
So here's the background for my case. I just got 2 Beolab 4000 Mk1 recently and I hooked it up to my Intel Mac Pro tower using the 3.5 mm head phone jack with a converter to RCA. With this setup everything is working fine and sounds great.
However, recently I picked up an additional pair of Beolab 6000 floor standing speakers, so I have this idea in my head to run 4 Beolab speakers with my computer setup. I would get a pseudo surround sound system. So in setting this up, I use the 3.5mm head phone to RCA cable and then split the RCA for the left and right side. So far so good. Since the Beolab 4000 are on my desk, to the left and right of me, the RCA RG6 cables linking them is 6 ft each. Now, the RCA RG6 cable linking the Beolab 6000, which I set it up behind me on the left and right (assuming that I am facing the computer), I have to use a 25 ft cables for them. And this is where strange things happens, when I hook these Beolab 6000 up. All of my speakers are picking up, at very low volume, AM broadcast from AM 1600. When I say low volume, I mean I have to put my ear right up to the speakers in order to make out what they are saying, but when you are sitting there in silence you can hear very low voices and it is just annoying. Not to mention that I spend so much money on the speakers. So I did some research and found out that AM 1600 broadcast station is about 2.2 miles from my house, which does not help with the issue. Also of note, this noise happens when the speakers are on and idle, if I play music or something, I am sure it is coming through, but when I turn the music off, I can hear it much clearer.
Now here's some of things that I did to try and eliminate the issue, but does not work.
1. I made sure that all of my RCA cables are RG6, which have better insulation that RG59. Didn't work/
2. I ordered cable from Bluejeancables.com and spending about 10 times more that the based RG6 cable to get a double shielded cable made by Belden model number 1694A, here's he link for your reference http://www.bluejeanscable.com/store/audio/ Didn't work.
3. All of the B&O speakers are plugged in a Monster Power Pro 900 Power conditioner, this is a surge protector that condition the power and make sure that it is always at 120 V and removed other electrical noise from the line. Didn't work.
So right now at this point, I am not sure what to do and how to get rid of the AM1600 board cast. If you know of anything that I may have missed or can try let me know. And like I said the issues only happens when I run Beolab 6000 with the longer wires.
Also is there something that I can used to get rid of the AM1600 signal or ground it somehow?
And my last wildcard idea which I have not tried yet, is to get a DAC and pre-amp to power the speaker and see if the signal is cleaner.
Thank you!
Art
Hi Art,
I don't have any immediate solutions, but I do have a couple of things to try.
Cheers
-geoff
Oops... forgot one more thing:
5. What happens if you plug the loudspeakers directly into the mains (in other words, don't use your power conditioner)?
Hi Art
A powerful AM signal like that is almost impossible to keep out of analog electronics and cables.
You should try the things Geoff suggested, as that may pinpoint exactly where the interference sneaks in.
In case the problem is indeed the cable, it may paradoxically help to use a slightly longer cable. If the current length resonates with the wavelength of the AM, it makes the problem worse. (We can't simply calculate the wavelength, because we don't know the speed of electrons in your cable - it is somewhat slower than the speed of light. So you can only test).
Ferrit beads are often suggested against EMI, but I don't know if they will help in a case like this. But it's cheap to try.
But as you said yourself, keeping the signals digital for as long as possible is definitely the thing to do.
Rune
Hi Geoff + Rune, please see my response to your questions below. Thank you so much for your help and suggestions.
What happens if you don't use the splitter? Either one pair or the other pair of speakers connected directly to your computer?
If I do this, then I don't pick up the AM signal, which is interesting. I would like to say that it is the splitter and cable length in combination that amplified the am noise issue.
What happens if you disconnect the RCA from the splitter and ground it so that the input to the wire connected to a loudspeaker is 0 V?
I would love to test this out but could you elaborate a bit further on how I may do this. Is there a device that need to buy to connect and ground the signal?
What happens if you keep the splitter but ground the 1/8" minijack (connect the Tip and the Ring to the Sleeve)?
Again I'm thinking that this may solved my issue, but I'm not sure how to approach this, would you please elaborate further?
What happens if you plug a completely different loudspeaker or a pair of sensitive headphones into the output of your computer? (in other words, is the problem inside your computer?)
I have another system that I used before the B&O and I tested it as well and there are no issues. It seems that the active speakers and wire length are part of the issue.
What happens if you plug the loudspeakers directly into the mains (in other words, don't use your power conditioner)?
Another good suggestion, I stated out doing just that and then since I tried so many things and issues does not go away, I then tried the power conditioner. And even after switching back and forth the issue still persists.
So at this point I have order an extra pair of cable for my Beolab 6000 and I increase the length to 35 ft, not that I need the footage but I figure it was worth the try.
Also I have order a set of Ferrite Clip-on as well. So I'll be putting them on all of the wires next week and then see what happen. It is interesting because in my research I found out that ferrite clip-on comes in different classes and the one that I need is Mix 75, which will target the am signal but that is harder to find so I order generic ferrite clip-on.
Either way I'll come back here and update you if any of these things solved the issues. If either of you come up with any more suggestion please let me know. I really want them to work and work well.