Hi everyone:
I'm a newbie, so I hope you'll be patient. I'm trying to fix a ground hum issue on my current A/V setup. The setup is fairly simple.
OTA Antenna--->3-way cable Amp-->TV--->Passive preamp--->Crestron Stereo amp via RCA
CD Player-->Passive Preamp-->Crestron Stereo amp via RCA.
I have no switch box and only a single input on the passive pre, so I'm swapping input cables to listen to a a diff signal source.
With the CD Player alone connected, I can't hear any hum or hiss whatsoever. It's dead silent.
As soon as I connect the TV output to the Passive Pre, I hear what sounds like ground hum, big time, but only if the antenna coax (RG6, IIRC) is connected to the TV. If I disconnect the antenna coax from the TV, the hum seems to disappear.
CDP, Amp and TV are all plugged into the same Tripp Lite surge protector with EMI/RFI filtering. That surge protector is plugged in to a grounded outlet. Removing the surge protector makes no difference.
The cabling is a bit hard to trace, but I believe the AC outlet is grounded to a subpanel in the basement. That subpanel, IIRC, has its ground connected to the main panel. The main panel, I'm told by two master electricians is properly grounded acc. to local code.
The feed from the TV antenna/CATV Amp, OTOH, appear to be grounded to a water tap outside. I believe this is the cause of my problems-different ground potential between the antenna cable and the Crestron stereo amplifier. The phone line also appears to be grounded to that water tap.
I want to get an electrician in here, but until I can arrange for that, I'm wondering the following:
Is my troubleshooting process sound here?
Is it safe to try to ground the Antenna cable to the Crestron amp's ground screw? That would tie both to a similar ground, but the antenna is outside on my roof. Wouldn't that be dangerous if there were a lightning strike?
I have been researching CATV ground loop isolators. The ones with the best reviews seem to be pricey. The Jensen VRD-1FF @ $USD 70.00 + shipping/taxes and the Viewsonics VSIS-EU, @ 60.00 + ship/taxes.
While I don't want to pay that much, the others are either from industry pro companies, (no reviews that describe audio quality) or junk. Other than, say, blocking fewer cable TV channels, do the more expensive ground hum isolators really allow better quality audio?
Whatever ground loop isolator I buy, I want it to allow all cable TV channels without anything being blocked. I see instructions for DIY, but I'm already swamped with other projects.
Thanks in advance
I'm a newbie, so I hope you'll be patient. I'm trying to fix a ground hum issue on my current A/V setup. The setup is fairly simple.
OTA Antenna--->3-way cable Amp-->TV--->Passive preamp--->Crestron Stereo amp via RCA
CD Player-->Passive Preamp-->Crestron Stereo amp via RCA.
I have no switch box and only a single input on the passive pre, so I'm swapping input cables to listen to a a diff signal source.
With the CD Player alone connected, I can't hear any hum or hiss whatsoever. It's dead silent.
As soon as I connect the TV output to the Passive Pre, I hear what sounds like ground hum, big time, but only if the antenna coax (RG6, IIRC) is connected to the TV. If I disconnect the antenna coax from the TV, the hum seems to disappear.
CDP, Amp and TV are all plugged into the same Tripp Lite surge protector with EMI/RFI filtering. That surge protector is plugged in to a grounded outlet. Removing the surge protector makes no difference.
The cabling is a bit hard to trace, but I believe the AC outlet is grounded to a subpanel in the basement. That subpanel, IIRC, has its ground connected to the main panel. The main panel, I'm told by two master electricians is properly grounded acc. to local code.
The feed from the TV antenna/CATV Amp, OTOH, appear to be grounded to a water tap outside. I believe this is the cause of my problems-different ground potential between the antenna cable and the Crestron stereo amplifier. The phone line also appears to be grounded to that water tap.
I want to get an electrician in here, but until I can arrange for that, I'm wondering the following:
Is my troubleshooting process sound here?
Is it safe to try to ground the Antenna cable to the Crestron amp's ground screw? That would tie both to a similar ground, but the antenna is outside on my roof. Wouldn't that be dangerous if there were a lightning strike?
I have been researching CATV ground loop isolators. The ones with the best reviews seem to be pricey. The Jensen VRD-1FF @ $USD 70.00 + shipping/taxes and the Viewsonics VSIS-EU, @ 60.00 + ship/taxes.
While I don't want to pay that much, the others are either from industry pro companies, (no reviews that describe audio quality) or junk. Other than, say, blocking fewer cable TV channels, do the more expensive ground hum isolators really allow better quality audio?
Whatever ground loop isolator I buy, I want it to allow all cable TV channels without anything being blocked. I see instructions for DIY, but I'm already swamped with other projects.
Thanks in advance
I don't know what type CoAx plug you are using but . . .
If your antenna lead terminates in a hand wired Belling Lee (IEC) type CoAx plug then you can screw it apart and cut back the screen braid till it no longer contacts the barrel of the plug. (Put insulating tape around any remaining braid just to make sure.)
If you have a pre-prepared moulded on plug you'd have to cut it off and replace it with a Belling Lee type plug modified as above.
If your antenna lead terminates in a hand wired Belling Lee (IEC) type CoAx plug then you can screw it apart and cut back the screen braid till it no longer contacts the barrel of the plug. (Put insulating tape around any remaining braid just to make sure.)
If you have a pre-prepared moulded on plug you'd have to cut it off and replace it with a Belling Lee type plug modified as above.
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Well, I'm not sure I want to be cable cutting just yet. Well, you know, not that kind of cable cutting.
I've been told that the transformer-type isolators affect the sound quality, and have a fairly significant insertion loss. No one has any experiences with different inline ground hum isolators?
I've been told that the transformer-type isolators affect the sound quality, and have a fairly significant insertion loss. No one has any experiences with different inline ground hum isolators?
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There are RF isolators as well. Some I guess are RF transformer based and others may just interpose small ceramic caps between the shield and the next device in the signal chain.
I have not heard the term OTA used in conjunction with cable before so possibly I am misunderstanding you. Is this actual cable TV or a cable to an antenna on your roof? (OTA to me signifies "off the air" and would be connected to a local antenna system)
I would not think you want to cut the shield and I assume grounding to the amp is a great way to fry it the next time you have a nearby strike.
Finding and Fixing Ground Loops in AV Systems | Electrical Construction & Maintenance (EC&M) Magazine
The set up you describe is conventional practice in most of North America, and is likely the safest approach.
I have not heard the term OTA used in conjunction with cable before so possibly I am misunderstanding you. Is this actual cable TV or a cable to an antenna on your roof? (OTA to me signifies "off the air" and would be connected to a local antenna system)
I would not think you want to cut the shield and I assume grounding to the amp is a great way to fry it the next time you have a nearby strike.
Finding and Fixing Ground Loops in AV Systems | Electrical Construction & Maintenance (EC&M) Magazine
The set up you describe is conventional practice in most of North America, and is likely the safest approach.
Hogwild:
Hope you didn't think that I intended the CoAx screen be disconnected at the equipment end as a permanent solution. I suggested it only as part of a trouble shooting exercise.
The suggestion was prompted by your statement that the feed from the antenna appeared to be connected to a water pipe outside and that the Crestron amplifier was separately grounded to a sub panel in the basement.
This, as you suggest, may be the cause of your problem. Differing ground potentials? Ground loop?
I would ensure that the CoAx cable screen is only grounded at one end, preferably at the equipment end.
Sorry if I am looking at this too simplistically.
Hope you didn't think that I intended the CoAx screen be disconnected at the equipment end as a permanent solution. I suggested it only as part of a trouble shooting exercise.
The suggestion was prompted by your statement that the feed from the antenna appeared to be connected to a water pipe outside and that the Crestron amplifier was separately grounded to a sub panel in the basement.
This, as you suggest, may be the cause of your problem. Differing ground potentials? Ground loop?
I would ensure that the CoAx cable screen is only grounded at one end, preferably at the equipment end.
Sorry if I am looking at this too simplistically.
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Yes, I did think that, so glad you cleared that up for me. Okay, it sounds like you all agree with my conclusion, that it's likely a diff. in ground potential.
Yes, it is an over the air antenna feed.
Disconnecting ground at one end of the antenna system may reduce the buzz, but then what about safety? What if I'm near the AV system when a surge or lightning hits? The antenna is on the top of the roof.
Yes, it is an over the air antenna feed.
Disconnecting ground at one end of the antenna system may reduce the buzz, but then what about safety? What if I'm near the AV system when a surge or lightning hits? The antenna is on the top of the roof.
I would try one of these: Amazon.com: TII 220 Ground Loop Isolator for Cable TV applications: Electronics
It would be connected in your antenna line at the piece of equipment where you want to break the ground loop.
Note that there are many others to choose from. (Ideally you should choose something that has UL/CSA approvals)
Do not mess with the antenna grounding! (Safety issue)
It would be connected in your antenna line at the piece of equipment where you want to break the ground loop.
Note that there are many others to choose from. (Ideally you should choose something that has UL/CSA approvals)
Do not mess with the antenna grounding! (Safety issue)
Hogwild:
Lightning storms are not so common in the UK and the usual practice is simply to connect the CoAx from the aerial dipole directly to the TV, with the screen braid grounded only at the TV.
The advice we get over here is simply to disconnect the aerial from the TV during a thunderstorm which, of course, is problematical if you happen to be away from home at the time! I certainly disconnect the aerial lead from the TV in my holiday home whenever it will be left unoccupied.
There has been a house fire in my village due to a lightning strike on its rooftop aerial, so it does happen, but that was over 30 years ago! The risk factor here would appear to be acceptably low.
It is possible to reduce the risk of lightning damage by looping external cables down to the ground, then up to enter the house. Some of the discharge will go to the earth at the loop, thus reducing the power that enters the house.
There will be different risks and regulations where you live and you may be required to run your cable through an earthing bar at the bottom of the loop or somewhere before it enters the house. In that case, I will bow out of the conversation!
Lightning storms are not so common in the UK and the usual practice is simply to connect the CoAx from the aerial dipole directly to the TV, with the screen braid grounded only at the TV.
The advice we get over here is simply to disconnect the aerial from the TV during a thunderstorm which, of course, is problematical if you happen to be away from home at the time! I certainly disconnect the aerial lead from the TV in my holiday home whenever it will be left unoccupied.
There has been a house fire in my village due to a lightning strike on its rooftop aerial, so it does happen, but that was over 30 years ago! The risk factor here would appear to be acceptably low.
It is possible to reduce the risk of lightning damage by looping external cables down to the ground, then up to enter the house. Some of the discharge will go to the earth at the loop, thus reducing the power that enters the house.
There will be different risks and regulations where you live and you may be required to run your cable through an earthing bar at the bottom of the loop or somewhere before it enters the house. In that case, I will bow out of the conversation!
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Yes. I ordered one from the U.S, but it turns out the business from whom I'd ordered it "CableTVAmps" on Amazon and cabletvamps (dotcom) may be fraudulent.
It's been 13 days since I ordered it, and the mail system's website tracking states it hasn't been picked up yet. The owner/rep. from cabletvamps insists it was picked up the day it was ordered.
I should have checked the handy Store Ratings & Reviews - ResellerRatings.com - Find Trusted Stores website before I ordered. 6 negative reviews on there, each giving the business a rating of 1 star out of 5.The first review states "probably a scam".
When I called the phone number listed on the cabletvamp (dot com) website, someone answered, announcing a diff. business name. When I asked him about cabletvamps, he told me he gets a lot of calls like mine, where "people are always asking me where their product is, cause they paid and weeks or months later, never received it".
So I cancelled that order with Amazon, and they are refunding my money. Note that cabletvamps.com also operates under the website broadbandamps (dot com) and also has a username on eBay, (I forgot it). The person knows he can rip people off with little, if any accountability.
After lots more phoning around, I requested a quote from a company in Canada for a TII 220, but have not heard back from the company rep after a few days (and it's a holiday weekend now, of course).
Te other models sold in the the US, (Jensen and Viewsonics) are very pricy. By the time I add in shipping and exchange rates, come to $CAD 90-100 each. I can't stomach that yet for something that basically amounts to two HQ resistors, a couple of coax connectors and metal shield. It's about $4.00 worth or parts!
On a side note, is there some way I can shut off this website's tendency to start pulling words from a website, when I have even asked the website to make the address an active URL? Very annoying.
It's been 13 days since I ordered it, and the mail system's website tracking states it hasn't been picked up yet. The owner/rep. from cabletvamps insists it was picked up the day it was ordered.
I should have checked the handy Store Ratings & Reviews - ResellerRatings.com - Find Trusted Stores website before I ordered. 6 negative reviews on there, each giving the business a rating of 1 star out of 5.The first review states "probably a scam".
When I called the phone number listed on the cabletvamp (dot com) website, someone answered, announcing a diff. business name. When I asked him about cabletvamps, he told me he gets a lot of calls like mine, where "people are always asking me where their product is, cause they paid and weeks or months later, never received it".
So I cancelled that order with Amazon, and they are refunding my money. Note that cabletvamps.com also operates under the website broadbandamps (dot com) and also has a username on eBay, (I forgot it). The person knows he can rip people off with little, if any accountability.
After lots more phoning around, I requested a quote from a company in Canada for a TII 220, but have not heard back from the company rep after a few days (and it's a holiday weekend now, of course).
Te other models sold in the the US, (Jensen and Viewsonics) are very pricy. By the time I add in shipping and exchange rates, come to $CAD 90-100 each. I can't stomach that yet for something that basically amounts to two HQ resistors, a couple of coax connectors and metal shield. It's about $4.00 worth or parts!
On a side note, is there some way I can shut off this website's tendency to start pulling words from a website, when I have even asked the website to make the address an active URL? Very annoying.
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No clue what you mean by "this website's tendency to start pulling words from a website" and don't understand what you mean by an active URL.
This isn't any forum behavior I am aware of, but you should report it in the forum problems forum.
What OS, browser, ad blocking software and anti-virus software are you using? (Include in your report)
This isn't any forum behavior I am aware of, but you should report it in the forum problems forum.
What OS, browser, ad blocking software and anti-virus software are you using? (Include in your report)
When you put a naked URL in a forum post, at some point the forum software parses-out the URL's "title" and puts it inside the link.
Amazon.com: Online Shopping for Electronics, Apparel, Computers, Books, DVDs & more
www.diyaudio.com
Edit history screen-grabs attached.
Attachments
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I had no clue what he was talking about, what you point to is a forum software behavior (feature) that goes back a long time. There are ways to trick it into not doing that. (Edit: those tricks no longer work)
We are migrating to xenforo relatively soon, this annoying feature is unlikely to be addressed.
We are migrating to xenforo relatively soon, this annoying feature is unlikely to be addressed.
I re-edited with a picture while you replied.
Yes, I know the "title grab" goes WAY back, and in fact is usually preferable to those gross over-long naked URLs that blow-out the right side of my monitor. And know we are moving soon.
Hogwild: a (tedious) trick is to manage the tags yourself. Type a normal sentence. Highlight the word/phrase you want presented as a link. Click the "world-chain" icon above the compose box, it asks for a URL. Paste your url. It displays like:
I just bought this book.
Note the link does not shout the linked-page's title.
The underlying code (but [] changed to {} to avoid parsing) looks like:
I just bought {URL="https://www.amazon.com/gp/product/0934041113/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1"}this book{/URL}
Yes, I know the "title grab" goes WAY back, and in fact is usually preferable to those gross over-long naked URLs that blow-out the right side of my monitor. And know we are moving soon.
Hogwild: a (tedious) trick is to manage the tags yourself. Type a normal sentence. Highlight the word/phrase you want presented as a link. Click the "world-chain" icon above the compose box, it asks for a URL. Paste your url. It displays like:
I just bought this book.
Note the link does not shout the linked-page's title.
The underlying code (but [] changed to {} to avoid parsing) looks like:
I just bought {URL="https://www.amazon.com/gp/product/0934041113/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1"}this book{/URL}
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