BFD is picking up HTPC em/rf 'noise'?

AngelEyes

Distinguished Member
I have been cursing my HTPC lately due to some nasty buzzing it creates through my speakers (not sub) when it is switched on.

However it is actually the BFD picking up the HTPC electrical 'noise' and not the processor as I first thought. If I disconnect the BFD, then noise is gone, however so is the subwoofer.

Random things I have tried so far:

Changing power leads for shielded / ferrite ringed varieties.
Run 'ground' wire between BFD and processor chassis

I am using Mark Grant Shielded cables for all connections.

Any suggestions on how to remove this annoying interference?

Danke,

Adam
 

Member 96948

Distinguished Member
If I disconnect the BFD, then noise is gone, however so is the subwoofer.
I'll have it. :)

The PSU for my SMS-1 created a really annoying buzz through my speakers after the poweramp arrived. That's no help I know. I'm just saying that I feel for you on this one and my thoughts are with you.

Russell
 

AngelEyes

Distinguished Member
Just when you have everything just right, things like this come along to test you... where is EvilJohn2 when you need him?

Adam
 

AngelEyes

Distinguished Member
I would try some of that ERS Cloth if I could just find someone in the UK who sells it :(

Adam
 

AngelEyes

Distinguished Member
Hmmm... disconnecting the analogue cables from the HTPC seems to improve things quite a bit.

Unfortunately they are of the 8 from 3 x 3.5mm jack plug variety and you can't get shielded versions unfortunately. Anyone know of a decent sound card with 8 x 3.5mm jacks or an RCA addin board?

Adam
 

AngelEyes

Distinguished Member
Not sure at all:(
 

Sniper

Active Member
Just to clarify: are you saying that this setup used to work perfectly, and now there's this noise? or has it been this way?

Also - do you need the analog out from the PC. PC's usually have a very 'dirty' analog out (fans & hi-frequency circuts are not good friends with clean sound) - why not use a digital out if you have one?
 

AngelEyes

Distinguished Member
Hi Sniper,

I have always used analogue so the noise has been there all the time but not too intrusive until I built my latest HTPC which obviously has some particularly 'noisy' components.

It is interesting that if I remove the BFD that the noise dissapears. I am hoping their is something here I can 'fix' rather than move to a digital output...

I use analogue because I want to take advantage of HD Audio from HD-DVD and Blu-Ray.

Adam
 

mattkhan

Distinguished Member
Hi Adam

possibly a v unhelpful post but I have had the same problem as you in the past and the only solution I could find was to use a digital connection. Interestingly I found that my hum came and went with the change typically occurring with times I had to take the lid off the PC and put it back on again. I think this says it was a grounding issue in my case but I could never reliably work out what triggered it.

I guess one approach will be for you to systematically dismantle your PC checking for hum after every change and seeing if you can isolate it down to a single component. This is a rather labour intensive task of course :suicide:

Cheers
Matt
 

abit_late

Active Member
I had the same annoying interference and it was because of a ground loop hum. You might want to try removing the earth wire from the BFD plug, at your own risk of course.
 

Mr Incredible

Distinguished Member
I had the same annoying interference and it was because of a ground loop hum. You might want to try removing the earth wire from the BFD plug, at your own risk of course.

:nono: Unfortunately the BFD's are not double insulated so removing the earth on the BFD would be a major risk. I removed the Earth on my sub and amp as they are both double insulated; same end result! No hum through the "BFD" chain.
 

AngelEyes

Distinguished Member
ok, so disconnecting the earth cable on the processor or sub might help?

Adam
 

AngelEyes

Distinguished Member
Ok, but it will have to wait. During some system re-builds yesterday I had to pinch my HTPC PSU to test a rig and seem to have fried it somehow... :(
 

Sniper

Active Member
Hi Sniper,

I have always used analogue so the noise has been there all the time but not too intrusive until I built my latest HTPC which obviously has some particularly 'noisy' components.

It is interesting that if I remove the BFD that the noise dissapears. I am hoping their is something here I can 'fix' rather than move to a digital output...

I use analogue because I want to take advantage of HD Audio from HD-DVD and Blu-Ray.

Adam

I see - I wasn't aware "HD" audio was decodable (!) on PCs (why not actually) - so until a digital connector of some sort makes it way on pc sounds cards (hdmi on a soundcard, but with video being looped thru'), you're going to have to play with grounds (as mentioned by others). I'm pretty sure it's a ground loop issue.
 

AngelEyes

Distinguished Member
Yeah, although if you read my post on the other av forum (in htpc section) you will see there is some debate as to whether Cyberlink (powerDVD) downsample all HD to 48hz/16bit anyway... :(
 

Sniper

Active Member
Yeah, although if you read my post on the other av forum (in htpc section) you will see there is some debate as to whether Cyberlink (powerDVD) downsample all HD to 48hz/16bit anyway... :(

hmn - heheh ... you might end up being better off with vanilla DD/DTS sound via digital then ... the noise should go away .... actually I would wire it both ways - analog & digital!

incidentally - all the wiring is going to the amp first? and then to the BFD (then to the sub)... or is the .1 from the soundcard being input to the BFD?
 
F

fullthrottleric

Guest
It would have to be going to the processor, otherwise no level control on the sub ;)
 

Mr Incredible

Distinguished Member
And if it wasn't through the amp then what a PITA if you then want to play some other source through the amp which requires the sub.
 
F

freekb

Guest
Hmmm... disconnecting the analogue cables from the HTPC seems to improve things quite a bit.

Unfortunately they are of the 8 from 3 x 3.5mm jack plug variety and you can't get shielded versions unfortunately. Anyone know of a decent sound card with 8 x 3.5mm jacks or an RCA addin board?

Adam

I've been having my eye on the ESI [email protected] for a while now - it should do the trick. It's amazing how much of a difference a good soundcard makes.
http://www.digit-life.com/articles2/esi-julia/index.html

In the uk you can get it from here: http://www.dolphinmusic.co.uk/page/shop/flypage/product_id/30864
 

Sniper

Active Member
It would have to be going to the processor, otherwise no level control on the sub ;)

I was pretty sure that was the case (i.e. thru' the amp)- thou' I was asking as it's possible to control the volume from the source - in this case the pc itself, since it's an HTPC setup, it's quite feasable to have a remote going to it ... with volume contol!

And if it wasn't through the amp then what a PITA if you then want to play some other source through the amp which requires the sub.

Never used a BFD - so don't know if the thing takes more than one input (one from PC, and other from LFE on amp)

But yes - I agree with both... it only makes sense thru' the amp - I guess I learnt to never assume anything ... and ask to make sure ;-)
 

AngelEyes

Distinguished Member
Well I am still having problems and it seesm really quite loud now especially listening at High Volumes.

I tried removing the earth from the Processor but that didn't help and it seems the Amp isn't double insulated so that didn't help.

I ran an earth cable between several components to see if it made any difference. Conecting the BFD and HTPC chassis actually made the noise even worse, no other combinations had any effect.

I also tried a power cord with ferrite rings on it on the BFD and HTPC again little effect.

Plugging the BFD into a mains socket in a different room helped slightly but is not a viable fix.

I tried using Digi-Coax from the X-Fi card to the processor instead but for some reason can only get 2.0 to come out... so gave up on that one.

I understand you can get ground loop transformers or something that can help, how do they connect up?

Thanks.
 

hoppaz

Well-known Member
Well I am still having problems and it seesm really quite loud now especially listening at High Volumes.

I tried removing the earth from the Processor but that didn't help and it seems the Amp isn't double insulated so that didn't help.

I ran an earth cable between several components to see if it made any difference. Conecting the BFD and HTPC chassis actually made the noise even worse, no other combinations had any effect.

I also tried a power cord with ferrite rings on it on the BFD and HTPC again little effect.

Plugging the BFD into a mains socket in a different room helped slightly but is not a viable fix.

I tried using Digi-Coax from the X-Fi card to the processor instead but for some reason can only get 2.0 to come out... so gave up on that one.

I understand you can get ground loop transformers or something that can help, how do they connect up?

Thanks.

I noticed a hum when I added a rotel power amp to my system. Did some reseach and apprantly cable reveivers receive ground loop problems through the cable coming into the house and this can be a problem for any system if your cable is linked in to it. There is a little fitting that you put on the end of the cable which reduces the interference. Do you have cable / telewest and is it linked up to your surround system.

Alternatively this might help...

http://cgi.ebay.co.uk/Interfearance...se-filter_W0QQitemZ140158414139QQcmdZViewItem


http://cgi.ebay.co.uk/Interfearance...se-filter_W0QQitemZ140158414139QQcmdZViewItem
 

Mr Incredible

Distinguished Member
Adam, just another thought. You keep mentioning "shielded" cable for the interconnects. Ironically this can be the source of the ground loop hum as well. THe shielding can provide a circuit for current to flow if different parts are at slightly different potentials. A shielded interconnect does not have to have both ends connected. As long as one end is earthed the shielding has what I believe is called a "floating" earth. All the benefits of shielding are still in place (i.e. any RF induced current will flow down one end of the shield.). So, have you tried a shielded cable between the amp and the BFD but with the shield ground snipped at one end?
 

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