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Hey folks, so i have a ground problem. I solved this with my main system using ATI amps like the AT528NC in my main living room but i wanted to go a bit cheaper and go with the monolith 7x200 watt amps. So i did exactly the same electrical wiring, dedicated 20 amp circuits to a sub panel made sure the grounds were starred everything. But that dreaded hum is there even using XLR cables from the marantz av7706. I even connected the chassis ground from each amp to my receivers ground screw but still no joy. Found out it was the directv coax cable. Now in the past i spent alot of money getting everything properly grounded on my directv system. This was the same issue i had using cheaper amps on my main audio system but when i upgraded to the ATI amps which are $$$$ than a monolith the issue was gone. I have done just about everything trying to fix the ground but that just isn't going to happen. So what are the thoughts on lifting the ground on pin 1 of each XLR? I really hate to do this but i dont know any other way to fix this. Is this going to effect my audio much? I tried to find something to lift the coax ground and when i stripped a coax down to bare wire and hooked up the receiver without a ground on the coax hum is gone however there is no possible way to terminate the RG6 cable without the shield touching. If i could find a way to do that, that would be preferred. But the ground lifts i saw only go from 5 to 1000 and none will work on directv because of the high frequency needs. So im stuck unless there is a way to jump the ground out of this coax. Just want some thoughts, ideas or what happens when i lift pin 1 of the XLR?
 

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Hey folks, so i have a ground problem. I solved this with my main system using ATI amps like the AT528NC in my main living room but i wanted to go a bit cheaper and go with the monolith 7x200 watt amps. So i did exactly the same electrical wiring, dedicated 20 amp circuits to a sub panel made sure the grounds were starred everything. But that dreaded hum is there even using XLR cables from the marantz av7706. I even connected the chassis ground from each amp to my receivers ground screw but still no joy. Found out it was the directv coax cable. Now in the past i spent alot of money getting everything properly grounded on my directv system. This was the same issue i had using cheaper amps on my main audio system but when i upgraded to the ATI amps which are $$$$ than a monolith the issue was gone. I have done just about everything trying to fix the ground but that just isn't going to happen. So what are the thoughts on lifting the ground on pin 1 of each XLR? I really hate to do this but i dont know any other way to fix this. Is this going to effect my audio much? I tried to find something to lift the coax ground and when i stripped a coax down to bare wire and hooked up the receiver without a ground on the coax hum is gone however there is no possible way to terminate the RG6 cable without the shield touching. If i could find a way to do that, that would be preferred. But the ground lifts i saw only go from 5 to 1000 and none will work on directv because of the high frequency needs. So im stuck unless there is a way to jump the ground out of this coax. Just want some thoughts, ideas or what happens when i lift pin 1 of the XLR?
At times with Denon/Marantz AVR/AVP's the trigger circuit, actually the ground return, is the issue. If you are using a trigger from the AV7706 to control the Monolith try disconnecting the trigger wire and see if that helps.
 

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At times with Denon/Marantz AVR/AVP's the trigger circuit, actually the ground return, is the issue. If you are using a trigger from the AV7706 to control the Monolith try disconnecting the trigger wire and see if that helps.
Yeah i tried that and no luck.
 

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The DirecTV coax is independently grounded, usually with a ground rod using a coax coupling block at the point where the coax from the dish enters the house. If this is the same ground rod used for the AC mains at the electric meter, it usually will not cause an issue. However if it is not, there can be a difference between what the two ground points actually see as "ground". This is what usually causes the ground loop. If you can't move the DirecTV dish to a location close the the mains entry, you may need to tie the two ground rods together with heavy wire (10 gauge or better) to help eliminate the problem.
 

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The DirecTV coax is independently grounded, usually with a ground rod using a coax coupling block at the point where the coax from the dish enters the house. If this is the same ground rod used for the AC mains at the electric meter, it usually will not cause an issue. However if it is not, there can be a difference between what the two ground points actually see as "ground". This is what usually causes the ground loop. If you can't move the DirecTV dish to a location close the the mains entry, you may need to tie the two ground rods together with heavy wire (10 gauge or better) to help eliminate the problem.
So here is the thing, i have already done this. I had an electrician and i verified this but the dish is on one end of the house and the service entrace/grounds rods on the other. I had them pull a heavy gauge IE #8 from the dish about 75 feet or more to the telco ground block which is new and was replaced. Where the directv dish is is also where the cable enters the home. The cable is properly grounded to a grounding block which is also tied to the dish. Then this is taken by the heavy grounding wire to the central ground where the telco/service entrance ground exists. This telco/service entrance ground was also renovated and new ground rounds which is all centrally bonded to the homes grounding system which is where the main electrical panel and everything grounds. There is a junction block they used to ground a wiring to a central point so that everything goes to the grounding rods which they drove 2 into the ground and wired them together with heavy gauge wire. Even with all that i have this coax hum. So now its what is next or what do i do. The thing is i had this hum on my main living room system when i used a "cheap" amp and pre amp. I then upgraded to an ATI class D amp and the marantz av8805 which has much better components i am sure and XLR's etc and that system doesn't hum anymore so im not sure why this one hums because the coax all goes to the same directv splitter which is also grounded to the same grounding point. The only thing i can think of that is different i have a APC J15 power a/v conditioner on my main system and all grounding points the AV8805, and 2 ATI class d amps are bonded to the TVSS grounding stud of the APC J15 power conditioner. Maybe that stopped the hum? I have something similar done in my masterbed room system where the hum exists but i dont have that fancy power conditioner i just ran grounding from the AV7706 to the 2 monolith amps to ensure grounding and that did help some it took it down about 30% less hum but its still very noticable. I am wondering if that would alleviate my issue if i use a similar power conditioner with the grounding stud on my system? The other option is to use a ART T8 ART T8 8-channel Hum Eliminator / Isolation Rack. This product https://www.sweetwater.com/store/detail/T8--art-t8-8-channel-hum-eliminator-isolation-rack I have ordered that and the APC H15 AV power conditioner but pretty much im chipping away at an issue im not sure if these will resolve
 

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Even with all that i have this coax hum. So now its what is next or what do i do.
Maybe try a grounding block at the rack at the receiver location, and connect it to the star ground connection locally, with a 12 awg cable or something. That's what I would try anyway. You can also see about running a chassis ground to the star grounding block you're using in the rack. They might be the same thing.

The thing is i had this hum on my main living room system when i used a "cheap" amp and pre amp. I then upgraded to an ATI class D amp and the marantz av8805 which has much better components i am sure and XLR's etc and that system doesn't hum anymore so im not sure why this one hums because the coax all goes to the same directv splitter which is also grounded to the same grounding point.
Sure, but a ground loop is based on ground potential differences between different reference points, not whether they're connected to a particularly problematic ground. It is the combination that matters, which is why it can be so frustrating. They can be a real PITA.

I have an older Marantz AV7005, which I bought specifically for the XLR balanced connections, and when I connected them to my DSP units, which have balanced inputs, I got a hum, while using the RCA outputs into the same inputs, with the - input shorted, I got blissful silence. I don't know if the outputs on mine, or yours, or whatever are actually balanced, both in having symmetrical differential signals, but also in output impedance, and a friend who works with them a lot looked smiled and nodded when I related the experience, so it makes me wonder, but I just went back to the RCA connections, accepted the 6 dB lower signal on the input, and it worked fine.

Now, IF those XLR connectors are in fact driven by truly balanced outputs, then yes you can, absolutely, simply not connect the ground. Will it work well? You'll have to try and see. But if all is good except when you connect the DirecTV coax, I'd exhaust those possibilities first.
 

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Maybe try a grounding block at the rack at the receiver location, and connect it to the star ground connection locally, with a 12 awg cable or something. That's what I would try anyway. You can also see about running a chassis ground to the star grounding block you're using in the rack. They might be the same thing.



Sure, but a ground loop is based on ground potential differences between different reference points, not whether they're connected to a particularly problematic ground. It is the combination that matters, which is why it can be so frustrating. They can be a real PITA.

I have an older Marantz AV7005, which I bought specifically for the XLR balanced connections, and when I connected them to my DSP units, which have balanced inputs, I got a hum, while using the RCA outputs into the same inputs, with the - input shorted, I got blissful silence. I don't know if the outputs on mine, or yours, or whatever are actually balanced, both in having symmetrical differential signals, but also in output impedance, and a friend who works with them a lot looked smiled and nodded when I related the experience, so it makes me wonder, but I just went back to the RCA connections, accepted the 6 dB lower signal on the input, and it worked fine.

Now, IF those XLR connectors are in fact driven by truly quality balanced outputs, then yes you can, absolutely, simply not connect the ground. Will it work well? You'll have to try and see. But if all is good except when you connect the DirecTV coax, I'd exhaust those possibilities first.
Likely the design is nominally balanced (check the box!), but the resistors in the circuit are likely 5% tolerance, which affects common mode rejection, and have higher values than necessary, which affects the quantity of resistor noise.

The balanced input must lead to a high quality differential amplifier. A differential amplifier is required as part of a balanced circuit to remove common mode noise. The balanced input is usually nosier than a SE input due to resistor noise unless is is very well designed and therefore costs more. Again the circuit may be not well balanced due to loose resistor tolerances in the differential amplifier circuit that combined with the balanced output result in poor common mode rejection.
 

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Discussion Starter #9
Maybe try a grounding block at the rack at the receiver location, and connect it to the star ground connection locally, with a 12 awg cable or something. That's what I would try anyway. You can also see about running a chassis ground to the star grounding block you're using in the rack. They might be the same thing.



Sure, but a ground loop is based on ground potential differences between different reference points, not whether they're connected to a particularly problematic ground. It is the combination that matters, which is why it can be so frustrating. They can be a real PITA.

I have an older Marantz AV7005, which I bought specifically for the XLR balanced connections, and when I connected them to my DSP units, which have balanced inputs, I got a hum, while using the RCA outputs into the same inputs, with the - input shorted, I got blissful silence. I don't know if the outputs on mine, or yours, or whatever are actually balanced, both in having symmetrical differential signals, but also in output impedance, and a friend who works with them a lot looked smiled and nodded when I related the experience, so it makes me wonder, but I just went back to the RCA connections, accepted the 6 dB lower signal on the input, and it worked fine.

Now, IF those XLR connectors are in fact driven by truly balanced outputs, then yes you can, absolutely, simply not connect the ground. Will it work well? You'll have to try and see. But if all is good except when you connect the DirecTV coax, I'd exhaust those possibilities first.
I tried all that didn't do much other than reduce the hum. So what i found is i purchased an ART PRO T8 Isolation Transformer. It did help about 90% of the hum was gone but it was still there. This went between the XLR's from the PREAMP and the AMP. It's not an actual ground lift but it was suppose to isolate the grounds but yea still hum/noise. So next step since my main system didn't have the same issue i went ahead and tried the Marantz AV8805 to see if it helped any and it did it took about 60% of the hum out because it supposidly has a better chasis and better isolation. So the next step i tried my ATI 528NC amp to see if that would get rid of the hum, it didn't. So same setup in my main room that has no hum connected the same way but no hum, hums in my masterbed room. I have tried just about everything. The one thing that seemed to work is i purchased an APC AV Power conditioner Model H15BLK. It has a coax surge supressor built in and supposidly helps with noise/ground loops. I connected it and it seemed to almost completely rid the issue about 99%. The problem is i need to make sure what my directv receiver needs for frequency range. I cannot seem to find anywhere if the directv C61K-700 client uses the whole 2 - 2450mhz frequency or is it just moca because its a client and not the acutal DVR because i may be able to get away with leaving it this way and/or using a ground loop isolator for coax. Your not suppose to run anything on the coax with satellite for various reasons but i don't know how else to solve this. The one other thing is you could still still hear a very faint you could tell the amps were on or switched off. So the next thing i did something that is not done in my master bedroom is i starred the grounds in the wall behind the outlets. This is already done at the panel box but i did it at both the outlets and panel box on my main system maybe that will help at least to try and make things the same. The only other difference is the PREAMP is using an APC J10 AV UPS which is similar to the H15BLK but it has battery backup. I have heard maybe that will provide cleaner power. So i am returning the H15BLK and buying another J10 AV UPS to make things the same and also i am purchasing the Marantz AV8805 instead since it did help and the ATI 528NC and 525NC since they are better units when it comes to isolation of circuitry and grounding etc. I am hoping this may alleviate my issue so that i dont have to run the coax through a surge protector or ground isolator.

The one thing i can say that i did do is i tried using a grounding block on the coax where the directv receiver is with a ground wire going to the amp/preamps etc to see if that helped and nope nothing changed.

I also tried unhooking the ground from the coax/dish to see if that helped, nope hum got worse.

So any thoughts do you think that UPS may make a difference? The only other thing that will be different at this point between the master bedroom and main system is on the main system everything is in a 42U rack whereas in my master bedroom everything is on a regular tv stand. I guess grounding can be accomplished the same fashion but running the grounds between all amps/preamp etc then run that to the TVSS stud of the J10 UPS.

Also to note these 4 20AMP circuits are all home runs to the sub panel. My main system is 4 20amp circuits to the Main Panel. The sub panel is new and hardly anything on it. I know the grounding is good i checked made sure its all tight there and at main panel and checked grounding rods, everything checks out and it all goes to a central ground block then to the ground rods.
 

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It's really hard to say with any confidence. I once had a ground-related hum/buzz on an active surround speaker. Both surround speakers, same model, plugged into the same power outlet, same power strip, the whole audio system was absolutely fine until I plugged in the projector, which was on the same power outlet as the surround channels, all of the same circuit, and it made noise in the right surround speaker, but not the left.

Eventually, I tried connecting to the right surround speaker with an RCA connector, as opposed to XLR which I was using for everything else, and that fixed it. I have no idea why, and I never found out. I moved, and never had that problem again.

On some devices, you can lift the 'signal' ground from the electrical ground, but you never want to defeat the chassis ground, as that becomes a potential safety issue.

You can connect the XLR cables without the ground connected, and try that. Or, if you have XLR inputs, you can run an RCA output, connecting the signal ground to the negative pin, and the hot pin to the positive pin, and float the ground on the XLR, or use it exclusively as a shield drain.

You can try a ground isolator on the Satellite, but it may not work. I don't know about the SWM interface, but with the older (and pre-SWM switch), the satellite receivers would connect either directly to the transponders, or to the old style switch, and send a combination of a 20 kHz tone and a DC Voltage of two different levels, I think it was like 13 or 18 volts, but don't hold me to that, and with that information the switch would which LNB and set of transponders to channel down the coax for a given station. I don't know if the SWM system, which does all kinds of fancy, still relies on DC. If the standard ground isolator is transformer based, it doesn't pass DC very well. There may be some magic product out there...

Food for thought, when the Satellite feed connects boxes together, it is also connecting ground connections together, so as maddening as it may sound, it is possible that there is a resolution that involves doing something to the ground on one of the other systems.

The other thing, is that if you can connect everything and get no hum until you plug in the satellite coax, try seeing if you can do that, but unplug all of the other connections from the satellite receiver, a.k.a., any signal connections, and I don't think it has a grounded receptacle, so maybe even make sure there is no conductive connection to anything on the receiver except for the power cable and the satellite feed. If that is good, you can see if you can use purely optical connections and see if there is cabling available to do what you need to do that doesn't use a ground. In the old days of component video and Toslink, you could just use the plastic digital audio cable, and then ground isolation transformers for the video signals. I know that there are some optical HDMI cables available, though I don't know if they actually bypass the ground, or still keep it to allow the +5V hot sync to pass through.

This is a bit expensive, but cheaper than upgrading all your components... I cannot say how well it works, but there might be something like it around with some digging that does the same thing, or well enough for what you need.

 

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The problem is i need to make sure what my directv receiver needs for frequency range. I cannot seem to find anywhere if the directv C61K-700 client uses the whole 2 - 2450mhz frequency or is it just moca because its a client and not the acutal DVR because i may be able to get away with leaving it this way and/or using a ground loop isolator for coax.
The C61K is DECA (DIRECTV's MoCA) only. It should say SWM-0 on the back near the coax port. So it doesn't need the entire frequency range. There are diplexers you can use to isolate DECA and SWM.
 
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