Sub Hum??

anjin007

All,

I have a brand new system with a PSW303 and the RM6005 sat speakers with a Sony STR-DE695 receiver. My problem is that the sub hums when I turn off everything so bad that I actually turn it off instead of the auto because it still hums. Mind you the reciever, tv, sat box and dvd are all turned off and it hums. I have wiring throught the walls and have a center hub behind the tv that the wiring from the reciever go to the speakers and sub. From the receiver I run a single RCA jack to a 2 RCA jack at the hub, then 2 RCA jacks from the wall at the sub to the single LFE in back of the sub. I switched it from the single LFE to the 2 Line in jacks in the back of the sub, same problem but now the low pass knob actually does something!! I also noticed that when I turn off the kitchen light I get a POP out of the sub!! Anyone have any ideas??

Dr. Spec

Ground loop. Start isolating components to find the offending items and user cheater plugs and it should clear up (hopefully).

anjin007

Please forgive but what is a ground loop and what are cheater plugs? Sorry but I'm a neophyte and not anywhere close to an audiophile. In layman's terms and I'll do great. I heard about the 75Ohm filter?? But the hum only happens when all power is off how is this possible when the sub is not getting any signal from the receiver?? Obviously the sub is still plugged in but nothing else is turned on.

walk

Ground loop is when you have 2 different ground points in a system. Very likely given your setup. What happens is that you get 60Hz AC power running over the audio cables (because the ground is closer there than over the actual ground wire, electricity takes the path of least resistance).

You can fix this with what's called a Ground Loop Isolator, about $15-20 from an eletronics store. They are very commonly used in car audio systems. I had to do this for the 24-foot cable run from my HT to my PC (so I can play AVI movies on my HT).

There are a couple of things you should try FIRST however.

First unplug EVERYTHING from the sub except the AC power. Does it still hum? If it still hums *loudly*, it's likely a defective unit and you should send it back. If it hums very quietly, like you need to put your ear to the speaker (or the port) to hear it, it's likely what's called "servo" hum. This is normal for servo-type subwoofers and there's nothing you can do about it. My CSW sub hums like this and all you can do is move it far enough away that you can't hear it. It's not very loud so this isn't a problem. If it's easily heard from across a room though, it's probably defective.

Second, if the above test fails to provide any results, move the sub near the reciever and plug it directly in, skipping your hub and in-wall wiring. If it doesn't hum there, it's probably a ground loop in your wiring and the GLI should solve it.

http://www.electronicplus.com/search-return.asp?search=ground+loop

dave shepard

Originally posted by anjin007
what are cheater plugs?

If I'm not mistaken it is a plug adaptor with no ground prong. First used in older homes with no ground in the outlets now can be used to help correct ground loop problems. But in the end the ground loop problem is still somewhere and has just been avoided. Someone correct me if I'm mistaken.


Dave

aba4430

Guys,
The 404 that I bought a few days ago did not have any hum, but last night after I turned everything off (sub on auto), noticed a dinstinct hum. The fact that there was none (I was on the lookout for any humming based on information in the owners manual) at the start and it just started, bothers me. Will troubleshoot based on above advice.
Regards,
aba4430

aba4430

Guys,
1. I have given my PSW404 a good shot so far and have not been able to get rid of the annoying hum. Per Polk CS, it is most likely the subwoofer amplifier transformer lamination hum. They said that I could get it exchanged, but did not guarantee that the replacement would be quieter. So I will be returning the 404 this week-end. Will upgrade to the 505 if I can. My 505 has been quiet as hell so far. Is the 404 doomed or what?
2. I was struggling with my main set-up for the past 3 months, and I am finally where I need to be (I think). Used the THX set-up mode on my 47TX (MCACC) and set all speakers to small (automatically done with 80 Hz as crossover). Set up the 505 as an THX Ultra SW. Watched concert for George this past week-end and noted a tremendous difference. Then watched The Fellowship Of The Ring and was again very pleased. What a damn difference vs. the previous set-up. The RTi100's have so much more impact now. This was contrary to what I believed previously, i.e. was purposely setting the 100's up as large, and without success. What is even more surprising is that the 505 totally rocks now. Shows how critical it is to get everything set up properly to get maximum benefit from the components.
Regards,
aba4430

ntculenuff

Subwoofer PowerCenter™ SW 200 with Clean Power Stage 1 v2.0
try this little bad boy..my sub used to pop when i turned on and off my ceiling fan/light. bought this and gone were the days of that annoying POP..its about 50 dollars and worked for me..

STUFFMD

Hey guys I know this is too simple...but I have the PSW 350 it has a volume or level control if you crank it all the way up or very close it will hum very loudly , just like all amps will. especially when everything else is off. Just turn the level down and you should notice a huge difference. This may not work for everyone...but start with the simple stuff....
Good Luck Stuff

ziggy0809

I have the PSW404 and I don't hear any hum at all....just lucky off the bat I guess...of course, I'm also now halfway to deaf too.



Cheers
Zig

ntculenuff

most hums in amps are caused by bad power input.. hissing or hummming in your speakers is usually caused by dirty power..
try some in line filtering such as ..panamax, monster..if it dont work take it back..couldnt really find an article on this on the net..
but i had static through my tv when appliances would kick on, but since adding the monster in line conditioner i would say that it is 95% gone