Ground Loop Hum and "Feedback" - AVS Forum
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post #1 of 30 Old 08-21-2012, 01:11 AM - Thread Starter
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Ok, I know there are many posts about this but without going through every single post, (which would be ridiculous to do) I'm not sure how to isolate this issue (no pun intended)eek.gif ........Ok so I've tried looking online but I have too many components to track this down by the means they mentioned. So my situation is....... I'm remodeling and until I finish (for a week or 2) I'm stuck using my backup t.v. with PS2 to watch movies:( I know...sad story). The ps2 is hooked to my sound system through an RCA to 1/8" converter cable and the conversion reverses from 1/8" to dual audio RCA that hooks into both AVR's aux input. I've always had a light hum in my speakers and subs...but using this equipment (old t.v. and PS2) has made it waaaaaaay worse!. I would like to take care of this issue now so that when everything is hooked back up properly, I won't have to deal with the hum anymore..... I have 2 AVR's, one amp, and one powered sub (and other non A/V related equipment) hooked up to a 24 outlet power strip (a total of 14 outlets are being taken up) on one side of the living/theater room, and on the other side of the living room, I have a 7 outlet, grounded surge protector with the T.V., PS2 (and other non A/V related items) plugged in. I have another powered sub plugged into the same wall outlet as the surge protector. I've tried the whole coax cable deal that's explained but when I unplugged both ends of the cable the humming continued without change. The worst hum comes from the the front sub (plugged into the wall outlet). I tried plugging this into a different wall outlet with no changed results. Both subs are powered hooked into 2 different AVR's sub pre-out connections. I'm trying to give as much information as possible. I've tried asking about the cable line but both the landlord and cable company claim to know nothing or have the ability to check it out and the box is located out of my reach (go figure) all this being said, there are seemingly a million different variables that could cause this issue. I was wondering if maybe there was maybe a cure-all or something that could be done at the point of hook-up i.e. speaker terminals, sub hook-up, AVR power/Amp power plug etc. I am willing to give as much information I have.


*********EDIT********
I should also mention that the hum in the main sub decreases significantly when the AVR's, and amp are powered off. I also decreases when the PS2 and TV are not only turned off but unplugged.

********EDIT AGAIN*******
I've narrowed it down to the RCA to 1/8" cable that I'm using coming from the PS/2. The hum is still there but a lot less noticeable. I would still like the whole humming in general issue addressed, but a solution to the RCA to 1/8" cable hum is needed much more as I have to deal with this for the next 2 weeks if I want to watch a movie.

While I am at it, if anyone could help me out with this second issue (which is not nearly as painstaking as the first) that would be great.
The above mentioned 1/8" to dual RCA cable that goes into both AVR's aux input is typically what I use for listening to audio off my laptop, Iphone, etc (anything that needs the 1/8" jack headphone input for audio). Anytime I want to unplug the 1/8" jack, I have to cut the power to the entire sound system otherwise I get a horrible continuous high pitched "feedback" from all the speakers. Is there anyway to fix this? I believe the issue is coming from the cable itself because I started out with 1/8" to single RCA and never had this problem, but I replaced the cable and I still have the same issue....Any solutions?

Any help with these issues would be appreciated
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post #2 of 30 Old 08-21-2012, 03:42 AM
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Go get yourself one of these:

http://www.radioshack.com/product/index.jsp?productId=2062214

Place it between the PS2 out and the rest of the world. When you unplug the PS2, just unplug it from this isolator, and leave the isolator attached to the AVRs. You might need an adapter or two to make all of that work, but you can figure that out on your own.

Nothing is 100%, but there's a pretty good chance this cures both of your problems.

If you still get hum and squeal when you unplug the PS2 and have the AVRs on, try just connecting the PS2 to one AVR at a time, see if you still have the problem. If the problem only exists when you have both AVRs connected, then post back here, we have more work to do.

One last thought, it never hurts to use good quality cables. Not expensive ones, just good quality. The stuff you get at the Shack isn't bad, should get you by for a couple of weeks and then some.
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post #3 of 30 Old 08-21-2012, 04:54 AM
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Quote:
Originally Posted by Matthew Reid View Post

I've narrowed it down to the RCA to 1/8" cable that I'm using coming from the PS/2. The hum is still there but a lot less noticeable. I would still like the whole humming in general issue addressed, but a solution to the RCA to 1/8" cable hum is needed much more as I have to deal with this for the next 2 weeks if I want to watch a movie.
While I am at it, if anyone could help me out with this second issue (which is not nearly as painstaking as the first) that would be great.
The above mentioned 1/8" to dual RCA cable that goes into both AVR's aux input is typically what I use for listening to audio off my laptop, Iphone, etc (anything that needs the 1/8" jack headphone input for audio). Anytime I want to unplug the 1/8" jack, I have to cut the power to the entire sound system otherwise I get a horrible continuous high pitched "feedback" from all the speakers. Is there anyway to fix this? I believe the issue is coming from the cable itself because I started out with 1/8" to single RCA and never had this problem, but I replaced the cable and I still have the same issue....Any solutions?
Any help with these issues would be appreciated

Ditto to Has7738's post. Start out with that < $20 ground isolator, and see what problems are still there after you install it. They may all go away!
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post #4 of 30 Old 08-21-2012, 01:12 PM
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I am not sure about the RadShack isolators being the best solution. Many devices like this simply use a resistor network (T or H-pad) to attempt to match impedance and isolate the ground path. Sometimes it works but most of the time is does not. I had a very good business for 10 years (until I was medically retired) building a transformer coupling device with a ground lift switch AND a variable attenuator. I sold these by the thousands to professional AV companies, the USG, Boeing, Lockheed, several showrooms in Las Vegas (The Riviera bought 50 at one time) and dozens of universities and traveling sales reps. They couple the stereo out from any PC or laptop into a balanced Lo-Z mic level output or, depending on the model selected, a line level hi or lo Z single ended connection to a sound system. They maintained the FR I have not had one single return for performance issues. The ONLY returns we had were to replace the input cable as iy was subjected to countless flexings in normal industrial use. This is expected and any cable will eventually need replacing. We also built them to take a licking. Even if all the lock nuts and knobs come off, the pot and switches and transformer etc remain solidly sealed together and will not rattle or loosen.

PM me if you want details.
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post #5 of 30 Old 08-21-2012, 01:30 PM
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Quote:
Originally Posted by Gizmologist View Post

I am not sure about the RadShack isolators being the best solution. Many devices like this simply use a resistor network (T or H-pad) to attempt to match impedance and isolate the ground path.

I've taken the RS ground loop isolator apart and it is composed of two small independent transformers. Nothing else but connecting and terminatiing wires.

I've also bench tested them with line level signals, sources and loads and their distortion and frequency response is excellent with all of the signals I tested it with, which covered the audio range and ran up to 3 volts rms.
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post #6 of 30 Old 08-21-2012, 02:18 PM
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Curious why they would use 2 transformers? Mine uses 1 xformer, 1 cap, 2 resistors and 1 pot.. most folks like the sealed pot as an attenuator as opposed to a slide switch pad. Excellent FR and SQ. Many of my clients ordered after using the RS stuff and other manufacturers.

I will go by one and check it out internally.
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post #7 of 30 Old 08-21-2012, 02:47 PM
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Originally Posted by Gizmologist View Post

Curious why they would use 2 transformers?
One for the left-channel, and one for the right.
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post #8 of 30 Old 08-21-2012, 07:35 PM - Thread Starter
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Ihad a very long day of work so I won't be doing much tonight but I'll check on all this tomorrow and get back on here. Thanks to everyone for the replies and assistance! Maybe if I gain some energy I'll hop on some of this tonight...
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post #9 of 30 Old 08-21-2012, 08:40 PM
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Silly me, I was thinking about my layout of stereo to mono and forgot he was maintaining stereo. Too little sleep.
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post #10 of 30 Old 08-24-2012, 02:21 PM
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Try using an old bit of cheap speaker wire as an earth strap between the case of the AVR and poweramp and see if that helps.

It's funny that in the day of turntables everybody knew the importance of an earth strap between components to overcome ground loop problems... but these days no one seems to do that any more.
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post #11 of 30 Old 08-24-2012, 07:38 PM - Thread Starter
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Try using an old bit of cheap speaker wire as an earth strap between the case of the AVR and poweramp
Should I do this for both AVR's?
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post #12 of 30 Old 08-24-2012, 07:48 PM
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Quote:
Originally Posted by Matthew Reid View Post

Should I do this for both AVR's?

Experiment and see what happens. It may or may not help. If the AVRs have a ground post for phono use that. Otherwise attach the wire under a screw onto the metal case.
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post #13 of 30 Old 03-07-2013, 07:54 AM
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sorry to jump in so late. but when you hook the earth strap from the chassis of the receiver (or the ground screw) to the amp, do you just hook it to the chassis of the amp also, or to a specific spot? I am having a horrible humming issue when i hook my cerwin vega XLS-15's and CV-1800 pro amp into my Onkyo 809 receiver. (its weird, they always have been right next to each other in the same outlet and they work fine seperately.. its just when i tried hooking everything up into surround sound, using the pre-outs on the AVR).

I damn sure love these forums. because onkyo customer support was no help at all, and acted like i was burdening them.. and i dont even want to start on Cox Cable.. sheesh.

Thanks for the help, and sorry mr thread starter for barging in.
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post #14 of 30 Old 03-07-2013, 09:19 AM
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Quote:
Originally Posted by kiwi2 View Post

Try using an old bit of cheap speaker wire as an earth strap between the case of the AVR and poweramp and see if that helps.

It's funny that in the day of turntables everybody knew the importance of an earth strap between components to overcome ground loop problems... but these days no one seems to do that any more.

Looks like a great way to make more ground loops.
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post #15 of 30 Old 03-07-2013, 09:25 AM
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Originally Posted by Gizmologist View Post

Silly me, I was thinking about my layout of stereo to mono and forgot he was maintaining stereo. Too little sleep.

BTW I ended up taking a bit of my own advice and using a RS ground isolator when a parametric eq inserted between my AVR and SUb started humming pretty badly. Ran into one of the nasty problems with cheap transformers, which is the absence of good shielding. The hum actually got worse depending on where I put the transformer. It wanted to fall into a bunch of power cords behind my equipment. :-(

At any rate I found that a small tin can such as a tomato paste can will often function as an excellent shield. I furthermore found that a tin screw-on cap such as one finds on say olive jars was a nice tight fit as it slipped into the tomato paste can. Who says that a Mediterranean diet isn't good for you? ;-)
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post #16 of 30 Old 03-07-2013, 09:57 AM
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Quote:
Originally Posted by NickThatStands View Post

sorry to jump in so late. but when you hook the earth strap from the chassis of the receiver (or the ground screw) to the amp, do you just hook it to the chassis of the amp also, or to a specific spot? I am having a horrible humming issue when i hook my cerwin vega XLS-15's and CV-1800 pro amp into my Onkyo 809 receiver. (its weird, they always have been right next to each other in the same outlet and they work fine seperately.. its just when i tried hooking everything up into surround sound, using the pre-outs on the AVR).

I damn sure love these forums. because onkyo customer support was no help at all, and acted like i was burdening them.. and i dont even want to start on Cox Cable.. sheesh.

Thanks for the help, and sorry mr thread starter for barging in.

The easiest place to hook up an additional ground would be to a chassis screw. Sometimes adding a ground can help. See here for more:http://www.jensen-transformers.com/an/ts_guide.pdf

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post #17 of 30 Old 03-07-2013, 12:08 PM
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Another point is that all grounds should tie to a common point. In pro gear systems, we use a large copper buss bar isolated from the racks and the racks are isolated from the building ground. The elctrical grounds are all tied to a common tie point (buss bar) and then connected to an earth (ground) . In a home system, try running a a separate 18 awg wire from a central junction to each piece of gear and connect solidly to the chassis.
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post #18 of 30 Old 03-08-2013, 06:47 AM
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well, here is what ended up happening when i got home from work yesterday.. Someone said to use a floater plug (just to isolate the problem, not as a permanent fix), but radio shack didnt have one. My handy neighbor was trying to dig one up, and while i was waiting, i pulled the hdmi cable that goes from the cable box to the receiver out. Boom, humming stopped, issue found. I didnt feel like buying this and buying that and waiting longer to fix it, and ive read that it simply means that the coax cable simply wasnt grounded properly. I live in an apartment, so there is no way of running a long ass wire from the cable box to a damn ground rod or any shenanagins like that. A peice of 16 gauge speaker wire from the splitter on the coax to the chassis of the amp (the only three pronged component in my setup), and badabing! Problem fixed. It was cheap, it isnt even visable with everything back in place, and Im good to go. Time to get more gear, and find new issues to fret over biggrin.gif
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post #19 of 30 Old 03-08-2013, 02:19 PM
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It always seems to be the cable. mad.gif

Glad you got it fixed, Nick!
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post #20 of 30 Old 03-08-2013, 05:16 PM
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thanks, me too. I just got back from the bar (took maximum advantage of happy hour), and now its time to let the neighbors know im home via loud, humless music biggrin.gif
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post #21 of 30 Old 03-13-2013, 07:35 AM
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ya know.. i noticed the hum comes back (nowhere near as bad as it was before, its completely bareable now, especially at the volume levels im usually at), and it is completely random. You just will be watching tv and eventually you will click on a channel and start to hear a TINY hum if you really listen again. Its weird how it comes out of nowhere like that. Honestly though, i can deal with it for now since its so quiet. Maybe ill eventually just grab a ground isolator or something, but as of now im gonna just roll with it i guess. Just thought I'd share that.
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post #22 of 30 Old 03-13-2013, 08:42 AM
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Originally Posted by NickThatStands View Post

ya know.. i noticed the hum comes back (nowhere near as bad as it was before, its completely bareable now, especially at the volume levels im usually at), and it is completely random. You just will be watching tv and eventually you will click on a channel and start to hear a TINY hum if you really listen again. Its weird how it comes out of nowhere like that. Honestly though, i can deal with it for now since its so quiet. Maybe ill eventually just grab a ground isolator or something, but as of now im gonna just roll with it i guess. Just thought I'd share that.

Probable cause is that your "fix" involved attempting to short out the ground loop rather than eliminating it.

I posted a fool-proof method for eliminating ground loops in: http://www.avsforum.com/t/1425569/ground-loop-hum-and-feedback#post_23052154
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post #23 of 30 Old 03-13-2013, 12:47 PM
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i feel like i read that at one point.. so what exactly do i do with the tomatoe paste?? or are you saying to go ahead and buy the little 10$ isolater thingy? I thought the issue was that the cable coax wasnt grounded properly, and grounding it to the same spot everything else in the system is grounded to was the idea. so thats why i did what i did, and it helped tremendously.

Let me know exactly what you think i should do, and ill try and give it a whirl. you have to understand, when the issue arose i read and read and read, and there are 8 kajabillion people with 72 trazillion different solutions to what seems to be the same exact problem for 75% of the folks. Tough to pick which is right. smile.gif
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post #24 of 30 Old 03-14-2013, 10:07 AM
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Jensen make a good Cable TV isolation transformer - VRD1FF that would prevent the ground loops you are having. You could also use a fiber optic HDMI between the cable box and receiver, but that is a more expensive option.

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post #25 of 30 Old 03-14-2013, 10:12 AM
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Quote:
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i feel like i read that at one point.. so what exactly do i do with the tomatoe paste??

Thicken the sauce (or 'gravy' if you're Italian) you've got simmering as you go about fixing your issues.

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post #26 of 30 Old 03-14-2013, 12:24 PM
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Thicken the sauce (or 'gravy' if you're Italian) you've got simmering as you go about fixing your issues.

I am italian, and i do call it gravy smile.gif

I guess the next time the buzz bothers me ill buy an isolator. it seriously only comes up on an occasion now, and pretty quietly. I dont often listen at low volumes. But eventually for peice of mind, ill get an isolator.
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post #27 of 30 Old 05-26-2013, 07:53 AM
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Quote:
Originally Posted by NickThatStands View Post

i feel like i read that at one point.. so what exactly do i do with the tomatoe paste?? or are you saying to go ahead and buy the little 10$ isolater thingy? I thought the issue was that the cable coax wasnt grounded properly, and grounding it to the same spot everything else in the system is grounded to was the idea. so thats why i did what i did, and it helped tremendously.

Let me know exactly what you think i should do, and ill try and give it a whirl. you have to understand, when the issue arose i read and read and read, and there are 8 kajabillion people with 72 trazillion different solutions to what seems to be the same exact problem for 75% of the folks. Tough to pick which is right. smile.gif


I'm in a similar boat. Yamaha 667 to ART Clean Box Pro (RCA) to amp input (XLR). AVR > converter > amp. I have 3 Altec 9444b amps that I am trying to drive off the yamaha's RCA pre out's in addition to the sub amp.

Now that I finally got around to hooking these EV/Altec 9444b amps up, I am having terrible ground loop noise from any channels of every amp. I tried plugging each amp, the AVR and ART Clean Box into a different house circuits (each individually and then the same) via 12/3 extension cord with no difference in the level of hum. I tried using a 3 way within each scenario to simulate a singular ground point. I thought that one of these things would have created a difference on the level of hum, but nothing changed. It's not a little hum, but a very loud noise. I used a self powered signal source (mp3 player) to test my understanding of ground loop theory and I am left with a slightly audible noise floor at a almost acceptable level with no ground loop hum! (this should simulate a lifted ground or optically isolated signal source as far as I can tell, but this is my first forray into this issue given a 110/120V power source)

So this is partial success as the hum is gone when the signal source is independently powered, but I still need to have the other components hooked up in the normal signal chain without the hum; but at least this has isolated the source of greatest potential for the ground loop exciting hum.

Can someone tell me if my thinking in this is askew?

I am aware of the gizmos. (the my most likely item of which I could purchase would be the http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=245-8650&scqty=1 and to augment all the channels of non-pro/unbalanced to pro/balanced the http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=248-6306&scqty=1 instead of buying another 3 art clean box devices) I am trying to avoid buying yet another little thing / multitudes of them to get the pro amps to play nice with my home audio gear. Interestingly enough, image results for ground loop search on google were helpful. In picturing the issue as a schematic, I thought that I can get something to work with some creative wiring/chassis grounding.

And that went like this:

I did some DMM testing via the grounding of the AVR chassis, am antenna plug et cetera, and decided to use the external antenna's ground terminal. (I used the antenna ground as it was quick and easy initially after trying a gaggle of other spots)
With the unit unplugged to verify my thoughts of providing a proper ground path without risking electrical damage to myself or the equipment, I used 16awg stranded wire for the trial as I didn't perceive solid core wire to make any difference, though I could be wrong in this thinking, and it was all that I had within a lazy arms reach. lol

In theory the idea of creating a singular ground source is sound (no pun intended) kinda worked, butttt, in practice I was only able to reduce the ground loop initiated hum by at least 50% in the audible range. All that means though is that I can still hear it quite easily, but it isn't quite as loud while ultimately still being equally annoying. Is there such a thing as a partial fail? lol

So what is next? Should I go and buy some random ground eliminator thing like the radio shack unit or go for the ART T8 8-Channel Transformer Isolator or XLR ground lift plug thing???

I would appreciate any and all thoughts, ideas, or real world recommendations.

Touche' reality!
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post #28 of 30 Old 05-31-2013, 04:42 PM
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Bill Whitlock has pages and pages of hum busting in his:

UNDERSTANDING, FINDING, & ELIMINATING GROUND LOOPS IN AUDIO & VIDEO SYSTEMS
2005 Generic Seminar Template
Instructor Bill Whitlock
president
Jensen Transformers, Inc.
Chatsworth, CA

http://www.jensen-transformers.com/an/generic%20seminar.pdf
video of the above seminar:
http://www.695.com/html/edu-vid-gr-loops.html

or this recent PowerPoint with added notes:

An Overview of Audio System Grounding and Interfacing
by
Bill Whitlock, President
Jensen Transformers, Inc.

http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

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post #29 of 30 Old 06-01-2013, 05:15 AM
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It's video links like the above that remind me why I hate iPads! smile.gif. Back to my laptop...

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

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post #30 of 30 Old 06-02-2013, 09:57 PM
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Quote:
Originally Posted by Speedskater View Post

Bill Whitlock has pages and pages of hum busting in his:

UNDERSTANDING, FINDING, & ELIMINATING GROUND LOOPS IN AUDIO & VIDEO SYSTEMS
2005 Generic Seminar Template
Instructor Bill Whitlock
president
Jensen Transformers, Inc.
Chatsworth, CA

http://www.jensen-transformers.com/an/generic%20seminar.pdf
video of the above seminar:
http://www.695.com/html/edu-vid-gr-loops.html

or this recent PowerPoint with added notes:

An Overview of Audio System Grounding and Interfacing
by
Bill Whitlock, President
Jensen Transformers, Inc.

http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf


Thanks for the links. I enjoy learning new things whenever I can.
So far I have concluded that my 3 Altec/EV amps have no issues as it was a faulty cable causing hum. I Have a EP4000 though that fails to respond to any solution however. With everything but the amp remaining fixed, untouched, whatever, I only am hhaving this hum on the behringer. Must be something wrong with the amp. The case was bent on 3 corners in shipping, so it must have received some sort of internal damage. I'll fiddle with it later as I am tired of messing with with it. Thanks to all who post here at AVS.
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