Notices

Question for you audiophiles

Old 12-07-2006, 08:45 PM
  #1  
Senior MemberCaptains Club MemberPLEDGER
Thread Starter
 
Join Date: Aug 2001
Location: West Carolina
Posts: 21,923
Default Question for you audiophiles

I just installed a Yamaha Sound Projector with sub-woofer. Please, no comments about getting not true 5.1 sound without rear speakers. I know that but it's great for the room it's in as well as my ears.

Now my question. I was going to try and use the DVD/CD player for the existing stereo as well as the YSP surround sound. When I hooked it up, the YSP sounds great. It plays from the TV as well as the DVD. However, when I power up the amp to play a CD I am getting a rather large hum thru the audio speakers. This is even with the YSP turned off. It even hums with the pre-amp off and it takes a while for the humming to "wind down". The YSP has it's own amp built in and the only thing I can think of is that it may be trying to backfeed thus creating the hum. I can remove the digital coaxil from the DVD player (even though it's not coax, just a RCA cord), and the video out to the TV. With both these wires removed from the DVD player the stereo is fine.

Any audio experts got any ideas? I can solve the problem by just getting another DVD/CD player and running two completely seperate systems but I was hoping to use the player I have for both.

Thanks in advance.
Shag is offline  
Old 12-07-2006, 10:21 PM
  #2  
Senior MemberCaptains Club Member
 
Join Date: Nov 2005
Location: seattle, wa
Posts: 5,934
Default Re: Question for you audiophiles

what kind of rcas are they? sounds like they are adding interference.
miike is offline  
Old 12-07-2006, 10:51 PM
  #3  
Senior MemberCaptains Club MemberPLEDGER
Thread Starter
 
Join Date: Aug 2001
Location: West Carolina
Posts: 21,923
Default Re: Question for you audiophiles

Nope, these are pretty thick quality wires. I can unplug the cable going from the "coaxil" port on the DVD to the YSP and also the video going from the DVD to the TV and the hum completely stops. One really weird thing. I can turn on the amp without the pre-amp and it will hum the speakers and contunue to do so for 10-15 seconds after I turn it off. I am stumped.
Shag is offline  
Old 12-08-2006, 12:43 AM
  #4  
Senior MemberCaptains Club Member
 
Garett's Avatar
 
Join Date: Feb 2003
Posts: 24,083
Default Re: Question for you audiophiles



It sounds like you are trying to amp an amp.

The humming continues after you shut off the amp is because probably the capacitors are discharging..........go easy on what you are doing because you will fry some power supplies.
Garett is offline  
Old 12-08-2006, 05:01 AM
  #5  
Senior MemberCaptains Club MemberPLEDGERPLEDGER
 
Join Date: Apr 2006
Location: Struggleville
Posts: 7,525
Default Re: Question for you audiophiles

I agree with Garett.
Bugbuster is offline  
Old 12-08-2006, 12:26 PM
  #6  
Senior Member
 
Join Date: Mar 2006
Location: Greensburg PA
Posts: 1,781
Default Re: Question for you audiophiles

Does the YSP have speaker terminal inputs or is it recieving a solely "passive" signal via the coaxial?

You can't amp and amp that would be "bad" but I don't think you "can" amp an amp in this case... The YSP has it's own integrated Signal Processor and most likely it's own internal, digital amp (I didn't read the specifics but I know what it does and therefore it most likely generates it's amped output to it's own speakers).

Signal cables and power cables do not mix so make sure that if you have any areas along the signal cable that a wall power cable crosses the signal cable that they cross at 90 degrees, this will eliminate or reduce 60Hz Hum, also you can install Ferrite Chokes on the Signal cable to eliminate hum.

If it's not 60Hz Hum it is possible that what you are experiancing is a ground loop, perhaps the YSP's internal amp is grounded to the chasis of the YSP. Is the back of the YSP or wherever the connections are, made of metal? If the amp in the YSP is grounded to the chasis and the same for the other components you can run into a ground loop situation. The cure is a cable which does not have a metallic inner sheild that is terminated into the ends of the cable. You may need a cable with one end not terminated to the coax connector so it can "drain" any potential between the two devices.

Without me actually seeing the setup to do a proper diagnosis I am just pulling straws here. Hum can be caused by numerous things.

StingerII is offline  
Old 12-09-2006, 04:42 AM
  #7  
Senior MemberCaptains Club MemberPLEDGER
 
Join Date: Nov 2003
Location: Dartmouth MA
Posts: 5,759
Default Re: Question for you audiophiles

I experienced a hum in my home theater set up and spoke tothe facory speaker res who advised something along Stingers recomendations. They told me to try to plug into different plugs to see if the hum went away. After several trys I found a plug on an opposite wall and the hum dissappeared. I think it was related to a cable tv line in one wall interfereing with the ac signal but I'm no expert for sure.
mymojo is online now  
Old 12-09-2006, 12:13 PM
  #8  
Junior Member
 
Join Date: Feb 2006
Location:
Posts: 9
Default Re: Question for you audiophiles

Switching plugs is a good idea.
Sounds like its a ground loop problem.

This guy breaks it down pretty well.
Earth loops are only a problem because the "earth" potential at different points in the various circuits in your house is not the same. This is mainly because of coupling - inductive and/or capacitive - between energised wires and earth wires, which puts a small AC potential on all of the earth conductors which differs depending on which active conductors each earth wire runs next to, and for how far.

When the earth potentials of two components are different, and you connect their earth planes together through a second conductor - like, classically, a shielded audio cable - you complete a circuit, and current flows through it. This current can, in turn, induce current in the very low level signal conductors of the cable. You'd never notice it if it happened to a high level signal, like a speaker cable, not that speaker cables have an earth wire anyway. The induced current in low-level signal conductors, though, produces hum or video interference, or various other problems.

Jaycar's primer on the subject (PDF) has a neat diagram showing what's going on. This ePanorama page is also excellent.

The Jaycar primer also discusses the really diabolical low level loops you can get with only signal cables involved, but those need not concern us now (thank goodness).

Your video cable is just another shielded connector, so when you plug it in between your computer and receiver, you create yet another bloody loop.

There are three ways to defeat earth loops. Well, three safe ways, anyway.

The first, and often the easiest, is to get the offending components' earths closer together. If they're plugged into separate outlets, plug them into the same outlet instead, with the help of a powerboard. When their plugs are separated by less house wiring, there's less opportunity for them to develop different earth potentials.

This, of course, isn't practical when you've got lots of interconnected equipment - even if you can hang a whole big home theatre system off one wall plate without blowing a fuse, you still shouldn't. But if you've only got two components that're still causing a problem and everything else is already isolated, then just shuffling power plugs and powerboards certainly can solve the problem.

Another solution is to physically break the loop, which is what the various isolators do.

One form of breaking the loop is an unsafe solution to the problem - if you just cut the earth conductors on the power cord of all but one participant in each loop, the problem is solved. But those un-earthed components may then, one day, try to kill you.

If you remove the earth conductors from all but one of the devices and then connect all of their chassis together you have the fairly safe version of this solution, but it's only practical in situations like professional recording studios. Apart from the inconvenience of doing this with home gear, it's bad practice to have devices that depend on another device for their safety earth sitting around your house.

Less alarmingly, you can often break an earth loop by cutting the shielding of the offending signal cables. They'll still be well enough shielded if they're only earthed at one end, or even if one half of them is connected to one component's earth and the other half is connected to the other. In domestic situations the amount of current flowing through an earth loop should be quite small, so this option is perfectly safe - it's quite possible for earth potential differences in home equipment to be large enough to give you an exciting little tingle, but it's only in situations where people decide to run earthed data cables between different buildings that there's likely to be enough potential difference between earths for things like electrocution or fire hazards to develop.

To separate earths when you're dealing with simple coaxial cables, you just take to the cable with a sharp knife (usual disclaimers apply) and "ringbark" it. Remove a "bracelet", a few millimetres long, of the insulation and the shielding foil or braid under it, wrap the area with ye olde electrical tape to protect the conductor underneath, and you're done.

The problem with doing this with a computer "VGA" lead is that it has its own earth wires, which are all tied to the earth of the device they plug into, if not tied to the shield-earth inside the plug as well. There are five ground wires in the standard VGA pinout; if you ringbark the shield and leave those wires in the cable then the loop will still exist. If you cut the earth wires in the cable as well, then the receiving device won't have the same earth reference as the sending one, so I suppose it might get the signal levels wrong. But this doesn't seem to happen when people just ringbark separate coaxial video leads, or when they use one of those expensive VGA balun doodads that you're trying not to buy (the primary purpose of those things is to allow you to run video a long way on cheap network-type cables, but they provide ground loop isolation as well). So I'm guessing that it's not actually a problem.

Cutting the wires isn't actually that hard if you can take apart the plug at either end of the cable. If it's one moulded lump, you might like to just bust the relevant pins off the connector at one end. A reversible version of this is painting nail polish or something on those pins, though you could still end up with capacitive coupling that way.
cornholio is offline  
Old 12-11-2006, 05:11 PM
  #9  
Senior MemberCaptains Club MemberPLEDGER
Thread Starter
 
Join Date: Aug 2001
Location: West Carolina
Posts: 21,923
Default Re: Question for you audiophiles

Thanks for all the replies. Just got back from 4 days in Michigan and had a lot of time to think about it. I finally decided to say f** it and get another CD player for the stereo. BTW, if anyone is wanting "surround sound" without running all of the wires, I'd take a listen to the YSP. It is NOT a substitute for 5.1 surround sound and won't work well in odd shaped rooms but I am impressed with what it can do with one speaker and a sub.

Thanks again!
Shag is offline  
Old 12-11-2006, 07:59 PM
  #10  
Senior MemberCaptains Club MemberPLEDGER
 
Join Date: Dec 2004
Location: Not in Texas
Posts: 10,213
Default Re: Question for you audiophiles

Shag - 12/12/2006 2:11 PM
It is NOT a substitute for 5.1 surround sound and won't work well in odd shaped rooms but I am impressed with what it can do with one speaker and a sub.




Eyeball is offline  
Old 12-11-2006, 10:23 PM
  #11  
Senior Member
 
Join Date: Mar 2006
Location: Greensburg PA
Posts: 1,781
Default Re: Question for you audiophiles

For those of you who would like true 5.1 Surround Sound, don't already have a ton of equipment and are not trying to fill a concert hall sized livingroom with sound check out the Sony DAV "Dream Systems" I am not a big fan of Sony at all, but I can recommend the DAV systems. They use Infrared to send the fifth channel audio to the rear speakers. Each rear speaker is self amplified (so they do need an electric outlet) but aside from that, they are wireless. And they work well. I set up a DAV900 series in my Mother's home and it fits in great with her silver Tosh 57" Plasma and silver audio/tv stand it looks "elegant" which makes the women happy and the lack of running rear wires is a plus.

Of course it's just mediorcre sound wise, but you would have to understand where I am comming from.. For MOST people they would be tickeled pink!

StingerII is offline  
Old 12-11-2006, 10:26 PM
  #12  
Senior Member
 
Join Date: Mar 2006
Location: Greensburg PA
Posts: 1,781
Default Re: Question for you audiophiles

dupe post
StingerII is offline  
Old 12-14-2006, 12:34 PM
  #13  
Senior MemberCaptains Club MemberPLEDGER
 
Join Date: Dec 2004
Location: Not in Texas
Posts: 10,213
Default Re: Question for you audiophiles

StingerII - 12/12/2006 7:23 PM

... check out the Sony DAV "Dream Systems" I am not a big fan of Sony at all, but I can recommend the DAV systems. ... Each rear speaker is self amplified (so they do need an electric outlet) ...
I am a fan of the idea of self amp’d spkrs but I have an issue with most of them. Many/most of the amp’d spkrs, and subs in particular, that I have seen scare the living crap out of me. They are basically cramming heat generating electronics with power supplies and transformers into a box of kindling. Not a problem unless/until things go wrong. That’s why you almost never see UL approval of an amp’d sub, they don’t pass the most basic of product safety guidelines. Doesn’t happen often but when an amp’d spkr fails the whole room goes up in flames.

Sony is one of the few companies that submits their amp’d spkrs, including subwoofers for UL approval. They either make ‘em safe to use or they don’t make them at all.

On the other hand, all of those notbook computer battery recalls are for Sony-made, UL approved batteries. They may be labeled as Dell, IBM/Lenovo, Toshiba, whatever, but they are all made by Sony. Interesting thing about them is that a quick check of the database for the manufacturing facility shows it located in China. ALL of those defective, Sony-made batteries are marked "Made In Japan". They are NOT made in Japan. The other interesting thing is that the sample batts submitted to UL for testing were from Sony’s Japan facility and passed rigorous testing for compliance to safety standards. The defective batts from the Chinese facility were never submitted to UL for testing. And yes, those defective batts are also marked with a UL approval. Humm ...



Eyeball is offline  
Old 12-14-2006, 04:11 PM
  #14  
Senior MemberCaptains Club MemberPLEDGER
Thread Starter
 
Join Date: Aug 2001
Location: West Carolina
Posts: 21,923
Default Re: Question for you audiophiles

Update. I took everything apart and put it back together completely isolating the YSP system from the stereo system. Everything was cool until I started putting the components back into the cabinet. When I set the DVD/CD player on the tuner, the hum started again. I picked it up a couple of inches and it stopped. Set it down and it hummed. I put a folded towel in between them and no hum. Then I tried again to run the RCA cables from the DVD/CD audio out to the preamp audio in and the hum started again. The DVD/CD player apparently is putting out some weird chit.

I have them plugged into the same outlet. Do you think it may just be some kind of short in the DVD/CD player? The YSP works fine and the stereo works fine. However, if they come in contact (even physical contact) the hum starts again. ???????

Shag is offline  
Old 12-14-2006, 10:35 PM
  #15  
Senior Member
 
Join Date: Mar 2006
Location: Greensburg PA
Posts: 1,781
Default Re: Question for you audiophiles

Like I said I am NOT a big fan of Sony.. Sony has been caught doing numerous shady things numerous times. But I do have first hand experiance with this system and for someone who has a wife and thus has to deal with "Wife Acceptance Factor" or "No Honey you can't have the real speakers they don't match the TV" the Sony system delivers the true 5.1 experiance.

The sub is pretty weak, but this is comming from a guy who builds his own subs... I am running a custom made 12" driver that's DUMAX'd at 23mm Linear ONE WAY excursion, in a critical overdampened enclosure (1Ft^2) fed 500 watts RMS courtesy of Bob Carver Sunfire TDC.



StingerII is offline  
Old 12-14-2006, 10:40 PM
  #16  
Senior Member
 
Join Date: Mar 2006
Location: Greensburg PA
Posts: 1,781
Default Re: Question for you audiophiles

Bo,

Does the DCD/CDP have "Metal" feet? I ask because if the metal feet are on a metal chassis and touching the metal chasis of the other components perhaps it's an issue of "Potential" maybe rubber feet are in order... Or, perhaps the sheilding inside the DVD/CDP is not good enough and it's leaking EMI to the cables or directly into the other components.

Have you tried different cables going from the DVD/CDP to the Stereo?

StingerII is offline  
Old 12-15-2006, 08:48 AM
  #17  
Senior MemberCaptains Club MemberPLEDGER
Thread Starter
 
Join Date: Aug 2001
Location: West Carolina
Posts: 21,923
Default Re: Question for you audiophiles

StingerII - 12/14/2006 10:40 PM

Bo,

Does the DCD/CDP have "Metal" feet? I ask because if the metal feet are on a metal chassis and touching the metal chasis of the other components perhaps it's an issue of "Potential" maybe rubber feet are in order... Or, perhaps the sheilding inside the DVD/CDP is not good enough and it's leaking EMI to the cables or directly into the other components.

Have you tried different cables going from the DVD/CDP to the Stereo?
I am not sure about metal feet or not but I can hold it an inch away and still get the hum. I have it sitting on a folded towel on the tuner and no hum at all. At this time there are no cables going to the stereo at all. I e-mailed Yamaha Tech support and will see what they say. The weird thing is that there are only two cables going to the DVD/CD, the "coaxil" (which isn't really coaxil) is going to the YSP and one RCA cable to the TV for video. EITHER of these cables will cause it to hum. This is when the YSP is turned off.
Shag is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread