Ground loop issue?

[robertbartsch]

I have an external stereo amp that is being driven by a 7.1 receiver with pre amp outputs.

When both units are powered up, no audible hum or hiss is present. However, when the receiver is powered off and the external amp is powered on, a loud audible hum is present.

Both amps are drawing power from a "protected" 120V power strip.

Is this a result of improper grounding? Should I run a ground wire from the chassis of the external amp to the chassis of the receiver?

Thx

[Robh3606]

Hello Robert

Normally the amp goes on after the preamp and goes off before to keep turn on/off transients out of your speakers. If you follow this regiment do you ever have a problem?? I noticed I had a hum when I accidentally turned off my Pre first. Wasn't bad though and normally everything is hum free.

Rob:)

[robertbartsch]

Thx.

If I turn the receiver/pre amp on first, no hum is present if the external power amp that is connected to the two front channels is turned off (receiver power amps are connected to 5 other speakers in a 7.1 HT system).

Hum is present in front channels only when the external power amp is on and the receiver/pre amp is off.

....so this is normal and, therefore, to avoid nasty driver damaging transients, I should never turn the external power amp on until [after] the reciever is on for a few seconds?

[SMKSoundPro]

Thx.
....so this is normal and, therefore, to avoid nasty driver damaging transients, I should never turn the external power amp on until [after] the reciever is on for a few seconds?


YES!!! this is normal!


Pre on 1st, Pwr on 2nd.

Pwr off 1st, Pre off 2nd.

It is a very safe habit to get into!

Scotty.

[1audiohack]

A power sequencer is a wonderful thing! If your not the only one that uses your system, and or you want safe one button opreation.

Check out the Furman Sound website, they make great sequencers.

If you don't want the industrial look, or can't hide it, Adcom made some pretty nice ones, the AC515 is usually available on the world wide garage sale for less than $100.00.

[boputnam]

I have an external stereo amp that is being driven by a 7.1 receiver with pre amp outputs.

When both units are powered up, no audible hum or hiss is present. However, when the receiver is powered off and the external amp is powered on, a loud audible hum is present.Guessing the interconnect is unbalanced (like an RCA...?) this is fairly normal.


Both amps are drawing power from a "protected" 120V power strip. By "protected" you mean a fused strip? That is not protection and is actually redundant to the fuse in the breaker box for that circuit.


Is this a result of improper grounding? Possibly. You may avert the condition if you are able to have balanced interconnects, but you are dealing with consumer gear and it typically does not offer balanced I/O. Pity.

Follow the advice you've received:

Power Amps are always LAST on, and FIRST off. :)

[robertbartsch]

....receiver is a consummer product but the power amp is a Crown XLS 802D - 500wpc. I assume it has balanced inputs....

...the inputs to the Crown are 3-pin connectors which are sliced into RCA plugs for the reciever pre-amp output.

[boputnam]

Ah, so the Crown is balanced but the consumer pre-amp is not. Your situation is not uncommon.

Spliced balanced to RCA are no longer true balanced.

None of this matters, though, so long as you Amps on last, and amps off, first. However, if you do develop 60Hz groundloop, you might try one of those Radio Shack in-line isolation transformers. Stereo pair, inexpensive and very effective.

(btw - I've been thinking of your symptom. I get something like it in SR. For instance, when the guitar player unplugs his cord from his guitar without putting the amp on standby. The amp sees that as an open circuit I guess.)

[JBL 4645]

Take a thin strip of wire that is insulated and attach it to the screw off one piece of equipment and attach the other end to each screw while going steadily around each and sooner or later you’ll isolate the humming.

[Audiobeer]

Do you have a cable hookup in the mix anywhere. If you disconnect your cable does the hum go away?

[robertbartsch]

Ok Audio Beer - I'll try that - good suggestion. I assume the answer is yes, since the hum is not present if the reciever is off.

Thx,

[Audiobeer]

On almost 99% of all the complaints such as yours I've experienced it was the Coax coming in fron cable that caused the problem. Mondail used to sell a "little blck box" that eliminated the problem.

[Chas]

Jensen have one called ISOMAX.

http://www.jensen-transformers.com/iso_vid.html

[JBL 4645]

I’ve just soldered up the LF low frequency for the bass mid on the Alesis RA300 with XLR and its reduced humming down a bit further over previous use.

[boputnam]

On almost 99% of all the complaints such as yours I've experienced it was the Coax coming in fron cable that caused the problem. In some instances, stripping back the shield and breaking it's connection can resolve the symptom. Connect only the signal wire.

FWIW, take a multi-meter and see if there is any potential between the coax signal and shield. If there is (I measured +9v at one point... :(), that will be your source. I subsequently cancelled cable TV and went satellite. :)

[robertbartsch]

..so I can disconnect a single cable and see if that cures the issue? I assume that would confirm an input wire issue.

What are balanced inputs, anyway?

[grumpy]

Did you disconnect your cable-TV coax cable from your system?

http://www.hifiportal.co.uk/Articles/Article0003-BalancedVsSingleEnded.pdf

http://www.yamaha.com/yamahavgn/CDA/ContentDetail/WrappedTextDetail/0,,CNTID%25253D48542%252526CTID%25253D227500,00.ht ml

[boputnam]

What are balanced inputs, anyway?:blink:

Here's a simple Google search on the string Balanced Inputs (http://www.google.com/search?q=balanced+inputs&rls=com.microsoft:en-us:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7GGIC).

But, you'd also benefit from doing more background research. Go to the Rane website, Library (http://www.rane.com/library.html) section (one of the few things Rane does really well... ), particularly their RaneNotes (http://www.rane.com/library.html#rnotes) and scroll down to their "Wiring, Interconnection and Grounding" section. Read every note posted there. cf Rane Note 110. It's legend.

As well, you should grab a sixpack and settle comfortably into the Rane Pro Audio Reference (glossary) (http://www.rane.com/digi-dic.html) - we've all done it. You'll never be the same... :)

[allen mueller]

:blink:

Here's a simple Google search on the string Balanced Inputs (http://www.google.com/search?q=balanced+inputs&rls=com.microsoft:en-us:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7GGIC).

But, you'd also benefit from doing more background research. Go to the Rane website, Library (http://www.rane.com/library.html) section (one of the few things Rane does really well... ), particularly their RaneNotes (http://www.rane.com/library.html#rnotes) and scroll down to their "Wiring, Interconnection and Grounding" section. Read every note posted there. cf Rane Note 110. It's legend.

As well, you should grab a sixpack and settle comfortably into the Rane Pro Audio Reference (glossary) (http://www.rane.com/digi-dic.html) - we've all done it. You'll never be the same... :)

Good suff on the rane site, I also like some of the articles on the Jensen site.

Might as well make it a 12 pack and read this too:

http://www.jensen-transformers.com/apps_wp.html

Allen

[robertbartsch]

Hum is still there when a single input cable is disconnected.

[Mr. Widget]

Hum is still there when a single input cable is disconnected.That won't change anything... if one is connected then the two devices are grounded together... your problem is that something in the system is not at the same ground potential as the rest of the system or something is broken.

Do you hear hum with nothing connected to the amp(s)? If yes, your amp(s) has/have an internal problem. If not, do you have hum with your preamp connected to the amp and no sources connected? If this causes hum and they are both plugged into the same power strip you either have a broken preamp or an improperly wired system.

If there is no hum with only the amp/preamp connected, add one source at a time until the hum appears.

If this is redundant to earlier posts, I'm sorry... I didn't go over the thread.


Widget

[boputnam]

Hum is still there when a single input cable is disconnected.Which cable are you talking about?

The suggestion was specific to the coax TV cable - drop the shield and use only the signal (center) wire, and see if there is an improvement. As well, we talked about using a multi-meter to measure if there is a potential between the signal and shield of the coax...

[lgvenable]

for my 2 cents

I had ground loop issues with 6 amps and my denon receiver, and I pretty much thought it was insolvable.

Lo and behold, I placed a 29.00 Behringer HD400 hum destroyer, between the unbalanced sub signal from my denon, and the balanced input into the amps. The hum absolutely went away, dead silence.

It works for all my amps, and I was able to crank then wide open (300 wpc on the stereo 2 channel amps, with the 2 channel sub amp bridged to 600 wpc). They are controlled by the pre-out Denon signal, but when turned on, and you are watching TV (as an example)...there is now no hum what-so-ever.

Previously, when you turned them up, it was awful.

The side benefit, is I get to keep the Furman conditioners & the Monster power center, and all the other stuff I bought for grounding and eliminating hum etc.; as I really did need some of the parts, but none resolved the hum. I searched the forum, and tried lots of folks suggestions, all to no avail.

If you have ground loop hum, try a Behringer HD400,it is a small 2 channel box with no power input. This was a problem I've chased for a year. The HD400 absolutely solved it, by itself. (as I unplugged everything I had bought and verified it solved the hum issues by itself.

And at 29.00 each, it was the best 174.00 + shipping I ever spent.

Larry

[hjames]

Thanks for the tip!
Amazon and lots of folks have it for $29.99 ...
(but Amazon has free shipping) ...
Just ordered one, I'll check it out -
HK Receiver -> Yamaha 31 band EQ ->biamp stuff

I found pix ...

[JBL 4645]

Don’t forget it’s a Behringer, Heather, but you already knew that.:D

I’m thinking about buying a few of these products at some later stage to tackle a few humming bird issues.

Sometimes I use some wire attached to one piece of audio equipment and it often solves the issue, but not always. Sometimes I have real pain in the neck ground/humming issue it would keep me up for hours.:banghead:

I’m surprised there’s no XLR connection on the back? So as and when I eventually buy a few, I’d have to use RCA to phone and phone to XLR, what a dogs dinner!:hmm::rolleyes::D

[hjames]

Don’t forget it’s a Behringer, Heather, but you already knew that.:D

:rolleyes::D

Yeah, but if I read this correctly, its not Active but passive -
and for $30, its not much of a risk, right?

I wouldn't buy anything of theirs that's ACTIVE

[Mr. Widget]

Yeah, but if I read this correctly, its not Active but passive -
and for $30, its not much of a risk, right?Yes and no... it is an isolation transformer. As such the likelihood of it failing is low, however transformers like speakers vary wildly depending on quality. High quality transformers will pass transients far better than lesser units and will in general have lower distortion and less likelihood of going into saturation. High quality transformers are not inexpensive.

I have no experience with this Behringer unit and it might be just fine, but I doubt it is as invisible as one from Jensen.

Widget

[hjames]

Yes and no... it is an isolation transformer. As such the likelihood of it failing is low, however transformers like speakers vary wildly depending on quality. High quality transformers will pass transients far better than lesser units and will in general have lower distortion and less likelihood of going into saturation. High quality transformers are not inexpensive.

I have no experience with this Behringer unit and it might be just fine, but I doubt it is as invisible as one from Jensen.

Widget

Well, I just had a Parts Express inline coax type filter on my CATV in line (to the TIVOHD) fail,
we recently lost part of our channels until I removed it from the line ...
so any kind of isolation device is worth a try ...
(can't live without BBC America and Topgear!!)

Do you have a link on "one from Jensen" ??

[JBL 4645]

Yeah, but if I read this correctly, its not Active but passive -
and for $30, its not much of a risk, right?

I wouldn't buy anything of theirs that's ACTIVE

I’m not sure if I’m following you on this “active?”

By that you mean active crossovers or other?

$30.00! I bet you can find it for less than $30.00! Look it up in Google product search, I’m sure you’ll find it at low, low, price.

[JBL 4645]

Well, I just had an inline coax type filter on my CATV in line (to the TIVOHD) fail, we lost part of our channels until I removed it from the line ...
so any kind of isolation device is worth a try ...
(can't live without BBC America and Topgear!!)


I can live without Jeremy Clarkson, can’t stand that guy.:rolleyes:

This car is real top performer in its own right. Its brutal horsepower is just exhilarating. It felt like the car was leaving the road and soaring for the skies.
:D

[Mr. Widget]

Do you have a link on "one from Jensen" ??They make a wide range of isolation transformers... I've used their video isolation devices for years without ever experiencing any performance degradation or failure.

Here are the audio isolators: http://www.jensen-transformers.com/iso_aud.html
Scroll down the page to find the relevant models. The CI-2RR at $178 seems to be quite similar to the Behringer. While the cost differential is quite high, the Jensen is quite reasonable considering it's high quality.

http://www.jensen-transformers.com/ci2rr.html


Widget

[hjames]

They make a wide range of isolation transformers... I've used their video isolation devices for years without ever experiencing any performance degradation or failure.

Here are the audio isolators: http://www.jensen-transformers.com/iso_aud.html
Scroll down the page to find the relevant models. The CI-2RR at $178 seems to be quite similar to the Behringer. While the cost differential is quite high, the Jensen is quite reasonable considering it's high quality.

http://www.jensen-transformers.com/ci2rr.html


Widget
Thanks for the specifics ...
After I check out the $30 device I've already ordered I'll consider $180 alternatives ...

[SteveW]

Hello again folks. Still lurking here and saw the thread. Boputnams' response about breaking the shield connection prompted me to add something here. I had a problem with a huge guitar rack full of stuff which was solved by lifting redundant shield grounds. Wasn't intentional, but it also eliminated the problem being discussed here. Here's a link to a thread I started on another forum to share my fix. Yea...it's all unbalanced guitar stuff but 100% applicable here perhaps. Hope it helps.

http://fractalaudio.com/forum/viewtopic.php?f=11&t=5366&start=0&hilit=hum

[opimax]

Heather ,

Got the same thing from sound express I think and lost HD local channels but got rid of the noise so I am in same boat you are. I had it w/both comcast and FIOS, current biggest annoyance w/sound system!

[Mr. Widget]

Heather ,

Got the same thing from sound express I think and lost HD local channels but got rid of the noise so I am in same boat you are. I had it w/both comcast and FIOS, current biggest annoyance w/sound system!You need to buy an isolation transformer with a broader bandwidth. The old Jensen VR-1FF video isolation transformer would lose some high def signals as well... they increased the bandwidth with their new model VRD-1FF.

BTW: I am not affiliated with Jensen. I just appreciate SOTA performance wherever I find it. :)


Widget

[hjames]

The old Jensen VR-1FF video isolation transformer would lose some high def signals as well... they increased the bandwidth with their new model VRD-1FF.


Widget

No - you are misunderstanding me - it worked fine for 6 months, but lately I noticed Comedy Central (and probably some others I don't use) was getting snowy. This indicates something is failing, its not a condition it had before ... its a device failure mode ...

[Mr. Widget]

This indicates something is failing, its not a condition it had before ... its a device failure mode ...I suppose anything can fail... that said, for anyone watching HD channels, you will need to buy a transformer that is up to the task. I am sure that inexpensive alternatives exist.


Widget

[opimax]

My system (last checked) was dead silent if I pull the cable wire out of it. I would appreciate some known working CHEAP solutions before I decide I am broke again which can happen as soon I am hungry, fix another speaker, want heat or A/C or just about anything ,lol

Mark

[hjames]

My system (last checked) was dead silent if I pull the cable wire out of it. I would appreciate some known working CHEAP solutions before I decide I am broke again which can happen as soon I am hungry, fix another speaker, want heat or A/C or just about anything ,lol

Mark

I'll let ya know once it arrives and I can test it!

[Mr. Widget]

My system (last checked) was dead silent if I pull the cable wire out of it.Then you absolutely need an isolation transformer on your cable feed... not at all an uncommon issue. You say you want a cheap fix. I'd call $50 pretty cheap. Isn't getting full video performance and no noise worth that? You should also check to make sure your cable drop from the pole or underground conduit is also grounded.

Widget

[opimax]

I bought the last 1 I saw recommended from parts express I think for 12, got rid of the noise but also a few stations!

I have FIOS which is fiber to the house so I am thinking it would be good to the house?

50 is nothing compared to the the frustration of the issue! But I thought the 1st one was going to take care of the issue. It has no name on the jacket so I would assume the manufacture is not proud of it :blink: Is this an "improvement" or will it make it go away all together?

If I remember correctly it didn't happen w/the built in amps in the Sony 9000es but when I went external to the 80's Perreaux amps. I don't remember if when for a short time I was usung the Adcom gfa 555 amps they made any noise. No gain controls where the Perreauxs do so maybe I am pushing the level up? or just sensitive equipment. Either way if it works I would take it for dbl the price!

Is checking for the ground something I can do? I would think probably if I knew what to look for...(hint hint :D)

Mark

[Mr. Widget]

Is checking for the ground something I can do? I would think probably if I knew what to look for...(hint hint :D)I think all of your questions have been answered above.

You could possibly have other grounding issues in which case a video isolation transformer will not help one bit. However, if as you say your system is dead quiet prior to hooking up a TV cable line, then your cable line is definitely at a different ground potential than your audio system. If this is the case, you need to properly ground the incoming cable, isolate it, or both.

If using a transformer solves the ground issue but causes you to lose a few channels, it is due to the poor quality of that transformer or the fact that it isn't a wide bandwidth design which is required for many of the newer channels.

How do you check if your cable feed is grounded? At the point the line from the street is attached to the line from the house there should be a junction with a screw terminal and a grounding wire that goes to a cold water pipe, or a grounding rod.


Widget

[hjames]

Is checking for the ground something I can do? I would think probably if I knew what to look for...(hint hint :D)
Mark

Do you have a volt meter?
You could use it to check for a potential (voltage) difference between the actual ground rod hammered into the ground by the CATV or Verizon Phone box outside your house (there SHOULD be one there to meet code back when you had wired phones - FIOS fiber doesn't need them)

[BMWCCA]

Do you have a volt meter?
You could use it to check for a potential (voltage) difference between the actual ground rod hammered into the ground by the CATV or Verizon Phone box outside your house (there SHOULD be one there to meet code back when you had wired phones - FIOS fiber doesn't need them)Quite some time ago we were having a big problem with lightning damage coming in over the phone line. The local TelCo checked the resistance in our ground rod and found it not up to snuff. Their solution was to connect it to the Electric Co. ground which ran to our could water pipe near the breaker box. No more blowed-up phones though. :blink:

[hjames]

I had checked outside and the CATV splitter outside was tied to the Telco ground rod. But it seemed like CATV induced hum had eaten up the TVI filter I got from Parts Express. When it failed I lost some of my CATV channels including BBC America - and I've got to have my Topgear!!

So today, the Behringer Hum Destroyer arrived from Amazon (free shipping)!
But its built for 1/4 phone plugs - fortunately I had 4 Phone to RCA adapters.
I pulled my left 4341 out from the wall so I could get to the back of the biamp rack.
The rack's signal IN coming from the LF and RF preamp outs of my HK receiver feeds the Inputs of the Yamaha EQ - I put the Hum Destroyer in between the HK preamp out and the Yamaha EQ In.
Powered everything up ... still got hum. Powered down again.

Checked my workbench and found an old CATV ground block device - basically its an F59 barrel mounted on a casting with a place to tie a ground wire to it.

I screwed that ground block down inside my biamp rack, and tied a heavy ground wire over to the ground screw on the JBL 6260 poweramp.

I pulled the beige CATV coax off my TIVOHD, (in the other rack with the HK receiver) and pulled it out of that rack.

I made a new (white) RG6 jumper and connected that from the ground block in the biamp rack to the TIVOHD in.
Powered the system up - no hum! Powered it down again.

For the moment of truth. I tied the beige CATV line from outside to the ground block.

Powered the system up - no hum! picked an empty input and turned the gain up to 0 (stupid loud!) Still no hum!!

Powered it down again. and closed everything up ...

Conclusion - now everything is on a common ground, no hum.

[boputnam]

Heather...

I'll bet you are relieved!

So, after all that, was the Behringer thingy critical? And, what the hell is it - an isolation transformer?

[hjames]

Heather...

I'll bet you are relieved!

So, after all that, was the Behringer thingy critical? And, what the hell is it - an isolation transformer?

Not sure the Behringer thingee is doing anything - seems like it was more a lack of common ground between CATV and audio gear. Would have been better if everything had been in a single rack, but I just don't have the room to do it that way.

Anyway, it's kind of a bear to haul the speaker off the wall with the biamp rack on top, so now that everything is back in position, I'll have to pull that Behringer gadget next time I pull everything out.

But - we just watched a TIVOHD "recording" of Numb3rs - its a cop show but done by Ridley Scott and his son - really nice 5.1 sound and such ...
Anyway, it sounded great, bass was very fine, and ... silent background.

Very nice improvement in the system!

[BMWCCA]

we just watched a TIVOHD "recording" of Numb3rs - its a cop show but done by Ridley Scott and his son - really nice 5.1 sound and such ...
Anyway, it sounded great, bass was very fine, and ... silent background.Glad it worked.
I'm a Numb3rs fan, too. Hard to believe the main character was Bernard, the kid elf, in the movie "The Santa Clause" and the dorky kid at camp in "Addams Family Values". That cracks my kids up.

Ridley Scott's other son, Jake, did the video of the creation of artist Robin Rhode with the new BMW Z4 "art car" painting by driving the car over "canvas" with paint-spray jets at the wheels. Don't know if it's really "art", but it's interesting. http://www.expressionofjoy.com/#

[boputnam]

Not sure the Behringer thingee is doing anything - Me neither, Heather.

There is no block diagram available - I suspect it is merely a Pin1 drop in a dull grey box.

When you next get bored, try and bypass it - I know, tedious, but my suspicion is your problem was elsewhere. And if true, anything Behringer that can be removed from the signal path is worth trying... :)

[hjames]

Me neither, Heather.

There is no block diagram available - I suspect it is merely a Pin1 drop in a dull grey box.

When you next get bored, try and bypass it - I know, tedious, but my suspicion is your problem was elsewhere. And if true, anything Behringer that can be removed from the signal path is worth trying... :)

from my long post ...
> I put the Hum Destroyer in between the HK preamp out and the Yamaha
> EQ In. Powered everything up ... still got hum. Powered down again.

Pretty sure that says it wasn't working against MY hum problem - but I got caught up in the troubleshooting logic and just forgot to pull it.

Again, my feeling is that the ground loop hum was the CATV ground - just like you said way way back. And all the "patches" I'd tried, from the radio shack isolation xfmr to the Parts Express inline coax thingee didn't really cure it. A hard ground wire cured it!

[Fred Sanford]

Me neither, Heather.

There is no block diagram available - I suspect it is merely a Pin1 drop in a dull grey box.

When you next get bored, try and bypass it - I know, tedious, but my suspicion is your problem was elsewhere. And if true, anything Behringer that can be removed from the signal path is worth trying... :)

+1 on the Behringer-ectomy, when you get access again.

+1 on Iso-Max, too.

Heather, sorry I hadn't read this thread before now, I've got quite the collection of isolation stuff (and experience with this kind of crap in AV systems). I just burnt out on troubleshooting-via-forum and even ground-loop discussions lately, so didn't even read the thread. Always feel free to call for stuff like this, real-time conversations are usually less frustrating for all involved. Glad you seem to have worked out a solution - can you elaborate on exactly what you did to ground the CATV? I'm curious whether this was the best long-term or worst-case-scenario solution from an electrical standpoint.

je

[hjames]

Glad you seem to have worked out a solution - can you elaborate on exactly what you did to ground the CATV? I'm curious whether this was the best long-term or worst-case-scenario solution from an electrical standpoint.

je

Okay ... the CATV cable comes from an outdoor splitter, which has a copper ground wire that runs to the TELCO ground round pounded into the soil.

The beige coax from the outdoor CATV splitter comes through the wall and was directly connected to the TIVOHD input (in the SCAN teak cabinet).

The TIVOHD was tied via RCA and such to the HK Receiver. Front preamp outs of the HK receiver run via long RCA cables to the Yamaha 31 band EQ in the Biamap rack where the Ashley crossover and JBL/UREI amps live.

The Ashley and JBL UREI amps are already tied together via their ground screws using solid copper bus wire I stripped out of some (new) 3 conductor household wiring.

What I did yesterday was remove the beige CATV coax (that ran from the outdoor splitter) and tied it directly to a grounded F81 barrel I just added to the biAmp rack. I ran a new coax I made up from the grounded F81 barrel over to the RF in on the TIVOHD.

The grounded F81 coax barrel has a solid copper bus line tied to the JBL/UREI amps and the Ashley.

Effectively, I created a solid copper ground bus between the CATV coax, and the existing grounds of the amps/Ashley/biamp rack.

At the moment, there is zero hum.

I wish all this stuff was in a common rack, but I don't have such a thing yet and am leery of going pure industrial in our TV/media room with a rolling
64 inch tall rack. I'd love a dual-width rack like TiDome has, but mine would be on wheels with teak or beech sides - but I don't have the room now, and until the CRT HDTV gets replaced with a flatscreen (not until it physically dies) , I don't see much of a redesign within that space.

But - I'll pull the Scan rack out soon - (sooner if I get that AVR-7300 today)
so I can reach around and get that Behringer out of the biAmp rack and ship it back to Amazon for a full refund ...

[boputnam]

from my long post ...
> I put the Hum Destroyer in between the HK preamp out and the Yamaha
> EQ In. Powered everything up ... still got hum. Powered down again.

Pretty sure that says it wasn't working against MY hum problem.Yeah, that's exactly the excerpt that caught my attention.


+1 on the Behringer-ectomy.That there is hilarious! :D


I wish all this stuff was in a common rack...Don't make that a goal, other than tidiness. Rarely does this alleviate / moot GL issues.


But - I'll pull the Scan rack out soon - so I can reach around and get that Behringer out of the biAmp rack and ship it back to Amazon for a full refund ...Well done! Class dismissed! :p

[hjames]

Its been a while, some of the gear in the system has changed since my last posing in this thread. Basically, the JBL/UREI amps have been replaced by a pair of Adcom GFA-555 amps,
which do NOT have XLR/pro type inputs ... somewhere in the changes a faint hum crept in again - but life has been busy and I haven't been on a bug-hunt to chase it down.

Anyway, with all the nonstop ads for FIOS locally - faster internet plus the promise of better picture quality, and some minor tech issues with COX CATV (as a method to increase bandwidth, they moved some channels to SDV - Switched Digital Video - meaning a group of channels is preselected at the pole, and not always available to my TIVOHD and cablecard - (unless I get a cable box and use THEIR DVR!)! Anyway, they eventually provided an add on CISCO router thing to handle that issue - but sometimes it drops out and the SDV channels are unavailable until I power-cycle the CISCO adapter.
Bottom line is sometimes BBC America and a few other channels I sometimes watch just aren't there for the TIVO to record.

Anyhow - FIOS doesn't HAVE SDV channels - so getting FIOS-TV, their version of "Cable" would eliminate that missing channels annoyance.

Its hard to get specific tech details on FIOS - they bring fiber directly to an interface box on the side of the house, have an indoor power supply with battery to run that box, and run COX to the places where you want your internet point or HDTV.

Since our basement and office are pretty packed - I prewired everything last week from near the old phone drop - ran fresh RG-6 from the basement to the AV rack, and I had previously run RG-6 up the side of the house, across the attic (more of a crawl-space vent area) and down into the office. Ready to go.

But the installer yesterday said he is required to install next to the breaker box to use that main ground point - which is the complete opposite end from the old gear, and far from my drops.

OK - sheesh - trying to be flexible - I decide to let him mount the interface where he wants, then run new coax into our office. I can use my existing coax to run his signal to the other end of the house and just barrel the "attic run" directly to the new COAX I had run for my AV rack and HDTV.

Take a few hours for all his stuff - but he gets the outside box done, the power supply is mounted in the laundry room by the breaker boxes - he runs coax along the main house power drops from the pole, although I warn him he could get hum from that, he says he's never had such a problem. But he does a neat job, gets his coax into the office, and puts a 2 way splitter at the end of it.


He brings in a wireless router/cable modem for the internet drop! I told him I already have 802.11N Apple Airport network in the house and have 8 existing wireless devices and I'm not going to change all of that, so I don't want a second network setup, but he says I can turn off the wireless in that gadget. (its probably the slower 802.11G network anyway).

Anyway, he hooks the router up to 1 leg of the splitter. We go through a lot of config stuff, but fortunately I've worked the Mac gear enough that I know how to configure it (and what NOT to change!) . I've got a cheat sheet with all my IP addresses in the house written down (for the printer, the TIVO, the various computers and
iTunes/Airtunes points in the house). I connect my Macmini directly to his router/cable modem and get them working ... I figure can tie in my Airport Extreme network after he's gone.

He sits at my desk and uses the browser (Firefox) to go to CNN, then surfs to some other site - then he announces that the software apparently won't install on a Mac. WTF - he never said he was going to INSTALL anything on my machinbe!! I told him windoes software won't install on a mac ... so - lets move on.

So, with the networking resolved, he he goes to hook up the other Coax to the splitter - the long run though the attic that goes to the AV rack. The moment he hooks it up, there is a HUGE HUM down in the TV room. I run downstairs to power everything down quickly, and he follows. He'd seen the speakers and rack and such when we started, but I guess it didn't really register.

Bottom line - every time we connected my coax to his splitter, Massive hum. I told him its a deal breaker - install is canceled, pull it all out.

He says he came to do an install and all he can do is stop and leave. I had him remove the cox from the outdoor interface, and unhooked his router (which he refused to take back with him). But nothing is the house is tied to FIOS interface box, I unplugged the basement power supply, and he had never actually gotten to installing the FIOS Cable card in my TIVO (I'd pulled the COX Cards and that CISCO adapter when he was doing the initial fiber drop to the home).

Took me an hour to restore the CATV connections, get the cable cards reinstalled, and re-config my internet on the CATV cable-modem.

But I'm back to my original barely audible hum - which I'll work on as time allows.
Speed test shows COX is (again) delivering 32/6meg rates.

The fun will begin next week when VERIZON will, no doubt, try to bill me for this fiasco.
But the install was aborted, I never had service on the TV and only had it for a few moments on one computer, and everything was powered off before the tech left.

Sheesh!

[JBL 4645]

Wow you sound like me on normal day.:D

MAD!:banghead:

Try a long wire and attach to one amp or AVR to these digital box things maybe somewhere along the route you might be able to isolate it. It may take a few minutes testing each device but its worked with me a few times.

Attach it to the (screw head) and tighten it down and then go around each and every device that the system is linked to.

On another humming issue when the fibre optical network was installed I tried out the digital network to the NICAM 725 digital VCR and all I got was a huge humming sound as soon as I connected the video output from the VCR to the AVR via the SCART video output lead

I haven’t located the bug yet its an odd one, the as the connection is sound, on the NICAM reception that is the audio is coming though crystal clear. As soon as I attach the SCART to the AVR HUMMMMMMMM!

Elusive!:blink:

I’ve disconnected it because I really don’t bother in watching British TV broadcasts. I didn’t even want the damn thing installed the TV stations can keep their digital HD fibre optic. But they had to install it because the council says, so well they can keep it as well. It doesn’t even do internet! Load of rubbish.

[hjames]

Wow you sound like me on normal day.:eek: MAD!

The usual load of rubbish.

Actually, I am not mad - as you just said, that would be your normal mode.

Perhaps you should read my last COUPLE of posts in this thread before popping in.
Try reading the post from 05-27-2009 09:08 PM - its been here for over a year now.

If you had read that, you'd know I had already grounded all of my gear together
with a copper wire within the equipment rack, AND done a NUMBER of things to suppress hum,
before this new issue arose. I even posted pictures (imagine that!) ...

[Audiobeer]

Actually, I am not mad - as you just said, that would be your normal mode.

Perhaps you should read my last COUPLE of posts in this thread before popping in.
Try reading the post from 05-27-2009 09:08 PM - its been here for over a year now.

If you had read that, you'd know I had already grounded all of my gear together
with a copper wire within the equipment rack, AND done a NUMBER of things to suppress hum,
before this new issue arose. I even posted pictures (imagine that!) ...

I know this is going to sound repetetive, But I'm not kidding you.....I had the exact same problem and "Aragon M.A.G.I.C. Power Box " cured all that. I don't think they even make them anymore. But if you buy one on ebay or wherever you can get one, If it dosen't work I'll buy it from you!

[herki the cat]

Do you have a volt meter?
You could use it to check for a potential (voltage) difference between the actual ground rod hammered into the ground by the CATV or Verizon Phone box outside your house (there SHOULD be one there to meet code back when you had wired phones - FIOS fiber doesn't need them)

herki'two cents:
I am not sure i understand whats in your system. In any case, you are much better off with only one ground point in your house according to the National Electric Codes and Underwriters Laboratories___ namely the AC power house entrance service cable neutral & the power company's ground wire in the same AC power house entrance service cable, both of which terminate connected to gether at your ac power circuit breaker panel to a massive grounding wire coming usually from your copper water pipe.

From that "prefered" common grounding point in your AC power entrance circuit breaker panel, a "star grounding system" to each audio equipment group in your Hi Fi Rack is highly recommended which connsist of a spearate ground wire going to each 120 volt, wall duplex outlet, privately dedicated to each audio equipment group in the rack, such that Ultimately, the green grounding wire in the power cord of each audio equipment component will be isolated in order to prevent ground loops & hum. It is equally important to avoid "daisy chian grounding and daisy chain AC power wiring configurations.

This green ground wire in the power cords is strictly a dedicated, isolated safety wire to which, the undedrwriters laboratory requires that "trash current dumps' shall not exeede five milliamperes total maximum from any source. Note: This is based on the fact that a "six milliampere shock" is leathal to a human.

Daisy chain ground wire configurations create disasterous ground loops. You should have a single dedicated ground to each isolated Major Equipment Component Metal Cabinet in the group, or at least to the each group.

Daisy chain configurations of 120 volt AC power to the indidual equipments also causes ground loops and Hum problems. This means isolated private 120 volt connection from indidiual AC power feed from the indidual isolated circuit breakers to each individual isolated wall duplex, aka: one for the power amplifier group___ one for the TV group, one for the low signal level preamps, & the turntable & CD Player etc.

Concerning the grounding of the TV Cable: This ground is ideally, and best achieved grounding the TV Cable "where it inters the house wall," preferably at the house foundation level to a water pipe such as an out- door water faucet outside at the house foundation level. If need be, have the TV cable routed under the house in the basement or crawl space all the way to the house water pipe location. This a perfect TV Cable hum solution.This approach also meets the "Star grounding "Critiria.

Note: If you drive a secondary ground rod for the hi fi, UnderWriters and the National Electrical codes require a "massive wire connection from that second rod all the way to the common ground point in your primary ground at the AC power sevice entrance circuit breaker panel. The reason for this is based on the requirement that there shall never occur any voltage differential __between the ac power neutral line which is solidly bonded to the house grounding panel__ and any secondary ground rod such as a separate ground stake, which believe it not is allways a very inadequate ground of unacceptable resistance performance. A five ohm resistance ground is a standard requirement for excellent audio performance.

Driving a non professional quality rod into earth of unkown earth resistance is very dangerous __don't do it!

[hjames]

Thanks for the tips - but, aside for the momentary Hum (Roar-hum) when the FIOS tech grounded his gear (and thus his coax) to the main breaker box at the other end of the house (and which may very well be on the other phase of the house's mains), and caused a roar-hum when it was connected to my existing gear via coax, the audio system is normally fairly quiet.

In fact, after my hum-busting just over a year ago, gain, the existing audio rack was silent. All the AV gear is plugged into a common electrical outlet, fed from a single breaker - they all have a common ground.

The house has copper water pipes, the old phone interface has a ground wire to a clamp on the outdoor faucet. The old CATV splitter outside is tied to that same ground clamp, and also to a long copper rod driven in the ground. I did not drive that rod - it appears to be ancient and I suspect was done by the original phone engineers. My audio gear is tied together, and has a coax cable tied to that outdoor ground point.

When I swapped out my 2 JBL/UREI amps for the Adcom GFA-555s, and then swapped the dead HK AVR-7300 for the Yamaha AV receiver, I picked up some hum - but only a minor bit, and nowhere near what we had when the FIOS was momentarily connected.

And frankly, if FIOS is that far off the ground potential of everything else- they won't ever be connected again.

The house is nearly 60 years old - short of opening up all the walls and doing a fresh rewiring into the TV room, what is there is pretty much not going to change.
We have 220 service in the basement, and like many older homes, that 220 service is split to provide 110v service in the home.
The Verizon tech plugged his power supply into a 110v outlet in the laundry room, near the breaker box. He lashed his coax run to the attic along the power mains on the side of the house, swearing he'd never had a problem with that before. He also said he hooked up Mac computers all the time, yet he tried to install some (apparently) Windows software on my mac. Since he was not knowledgable about Apple computer and a number of other things, I'm guessing he was wrong about other things as well. But all his gear is unplugged, the coax is disconnected from the FIOS interface box, and is not connected to anything in the house.





herki'two cents:
I am not sure i understand what's in your system. In any case, you are much better off with only one ground point in your house according to the National Electric Codes and Underwriters Laboratories___ namely the AC power house entrance service cable neutral & the power company's ground wire in the same AC power house entrance service cable, both of which terminate connected together at your ac power circuit breaker panel to a massive grounding wire coming usually from your copper water pipe.

From that "prefered" common grounding point in your AC power entrance circuit breaker panel, a "star grounding system" to each audio equipment group in your Hi Fi Rack is highly recommended which consists of a separate ground wire going to each 120 volt, wall duplex outlet, privately dedicated to each audio equipment group in the rack, such that Ultimately, the green grounding wire in the power cord of each audio equipment component will be isolated in order to prevent ground loops & hum. It is equally important to avoid "daisy chain grounding and daisy chain AC power wiring configurations.

This green ground wire in the power cords is strictly a dedicated, isolated safety wire to which, the underwriters laboratory requires that "trash current dumps' shall not exceed five milliamperes total maximum from any source. Note: This is based on the fact that a "six milliampere shock" is lethal to a human.

Driving a non professional quality rod into earth of unknown earth resistance is very dangerous __don't do it!

[BMWCCA]

The house has copper water pipes . . .

The house is nearly 60 years old

Ditto here, but the difference is we're on a well. Which means all that copper water pipe is above ground and the only connection to ground is our buried ABS plastic supply line from the water system in a detached garage to to the house. Not sure you get a great ground from ABS pipe, no matter how deep you bury it! But then it's probably not a contributor to ground loops, either. ;)

The funny thing is our main power-supply at the breaker box is grounded to our water pipes.

[hjames]

Decided to investigate further this ground to the Mains that the Verizon FIOS guy insisted he had to do ... It's hot and humid (and getting dark) so I didn't duck behind the bushes to get a closer picture - but - it looks like he ran a skinny green ground wire from the FIOS ONT (Optical Network Transition) box over to the electric power meter.
I'll check the junction further tomorrow, but I didn't see any super ground rod or anything like that at this end of the house.
Maybe its tied to the gas or water pipe somewhere inside ... but it looks like that skinny green line is it.

4607146072


He also undid the cable ties lashing the COAX to the power MAINS to see if that would stop the hum - and apparently just left it swinging in the breeze afterwards...!
46070

[SEAWOLF97]

He also undid the cable ties lashing the COAX to the power MAINS to see if that would stop the hum - and apparently just left it swinging in the breeze afterwards...!


Wasn't FIOS the commercial with their installation guy competing with the cable guy ?

the cable guy = fat/messy/confused
FIOS guy = trim/competent/on top of it all ????

I shouldn't laugh ....starting to get a hum after system is on a while ...had amps checked ..they're OK...just dread tearing it all apart ...we have NO grounded outlets.
Think wiki called it a "floating ground" :( , standard in 1960's homes.

[herki the cat]

Ditto here, but the difference is we're on a well. Which means all that copper water pipe is above ground and the only connection to ground is our buried ABS plastic supply line from the water system in a detached garage to to the house. Not sure you get a great ground from ABS pipe, no matter how deep you bury it! But then it's probably not a contributor to ground loops, either. ;)

The funny thing is our main power-supply at the breaker box is grounded to our water pipes.


herki's two cents:
My friend, CCA, I always enjoy your sense of humor, this time: "a great ground from ABS pipe, no matter how deep you bury it! "

However, there are serious over tones here. Quote: "our main power-supply at the breaker box is grounded to our water pipes." Now, IF the electriction who installed your house AC Power meter receptical & house entrance AC power system "merely assumed that your water pipes are buryed under ground" and failed to install a professional certified grounding rod connecting to your breaker panel AC power neutral line which is also bonded to all the safety ground wires in your house wiring that ultimately interface with the green wire in equipment power cords etc.

This is not likely the case, but if there is any thing I have learned, it is "never make assumptions about any thing." Have a look to see if there is a fat wire going from your circuit breaker panel box to a grounding rod in that area of your house.

[herki the cat]

Decided to investigate further this line ground to the Mains, the Verizon FIOS guy insisted on, but it looks like he ran a skinny green ground wire from the FIOS ONT (Optical Network Transition) box over to the electric power meter. I didn't see any super ground rod at this end of the house. Maybe its tied to the gas or water pipe inside He undid the cable ties lashing the COAX to the power MAINS to stop the hum - and just left it dangling. 46070

Herki's two cents:
:dont-know: it looks like your Fios tech has a bad problem. I can't get mad at the poor fellow; Fios hardware is exremely complicated. I have seen my daughter's Fio's massive hardware installation mess. No contest compared to the simple elegant equipment of ComCast Inc., whose Video programing, & Telephone service & Fast Internet are all very reliable, which I like very much.

Don't take my medicine; I am a Quack; but I would find some way to switch over to ComCast whose technical service is very fast and complete, no matter what issue comes up.

[hjames]

Herki's two cents:
:dont-know: it looks like your Fios tech has a bad problem.

... but I would find some way to switch over to ComCast whose technical service is very fast and complete, no matter what issue comes up.
Cable is nearly always a local monopoly - in my area, we can have COX CATV - comcast doesn't serve our area - but honestly speaking, all these contracted installs are about the same ... :crying:
Now that the holiday is over, I'll be expecting a call/email from Verizon wanting their money ...:eek:

[jcrobso]

Ditto here, but the difference is we're on a well. Which means all that copper water pipe is above ground and the only connection to ground is our buried ABS plastic supply line from the water system in a detached garage to to the house. Not sure you get a great ground from ABS pipe, no matter how deep you bury it! But then it's probably not a contributor to ground loops, either. ;)

The funny thing is our main power-supply at the breaker box is grounded to our water pipes.
Then use a 10ga wire to hook your ground to the copper pipe!

[herki the cat]

I have an external stereo amp that is being driven by a 7.1 receiver with pre amp outputs. Wwhen the receiver is powered off and the external amp is powered on, a loud audible hum is present
. Both amps are drawing power from a "protected" 120V power strip. Is this a result of improper grounding? Should I run a ground wire from the chassis of the external amp to the chassis of the receiver? Thx

herkie's two cents, revision #1:
Those protected power strips use "MOV" surge supressors that fail and leak stray current from the 120 volt line to the green ground wire in the power cords, thus creating a ground loop. Try removing that power strip, and use something else that has simple unprotected AC power outlets.

MOV's are very poor and degrade rapidly with simple surge hits causing contamination of the green ground wire which is there strictly as a safety ground wire, aka for personel protection in case of raw AC current shorts or leakage to the equipment cabinet. The clamped surge energy also rings like hell contaminating the neutral and AC line circuit beyond belief.

If you feel you need surge protection, go to "Zero Surge.com" This company has a superb surge protector of advanced technology that never contaminates the green ground safety wire and it passes Underwriters Laboratories EEE Compliance testing of zero failures when subjected to 10 years of lighting stroke events. This device is used 100% by the US Goverment in the Pentegon offices to protect hundreds of computers, as well as Hundreds of Business offices that can not tolerate computer down time.

Zero Surge products do not shut down the AC Power delivery in the event of any Surge including Storm Lightening events. This is professional quality Technology. There has never been a failure to Capture a Surge of any kind by "Zero Surge Products" in the 20 years of Zero Surge Production.

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