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hum job

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Dreamer

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Posts: 1616

Joined: Mon Oct 30, 2006 1:17 am

Location: Washington, NC

Post Thu Jan 01, 2009 6:27 pm

Re: hum job

aa7679,

When I first got my Velodyne sub, I had a lot of problems with a 60-cycle hum too. It took me about a month of messing with it to figure out what was causing it. It turned out that it was related to my cable box--apparently cable systems are NOTORIOUS for creating ground loop problems when connected to a stereo system. My solution involved connecting the cable box to the receiver with an optical TOSLINK cable instead of the digital coax, AND putting a ground loop isolator between the outs of the receiver and the ins of the sub, AND putting the cable box and TV on their own surge protector, separate from the rest of the system. My sub would even hum if it wasn't hooked up to the receiver like yours, and in the end it was almost all about the power--NOT the cables, the components or the sub itself. Connecting the cable box to the receiver via digital coax introduced a little more hum to the sub AND made my main speakers hum too, but the sub's main hum was pretty much all caused by the power connection, when it was on the same circuit as the cable box and TV. Most AV gear, apparently, has a completely different kind of grounding topology than most stereo gear, and causes all sorts of problems...

I would suggest putting the sub on it's own separate power strip--get a good one with fast clamping and a high joule rating. It doesn't need to be a super-high-dollar unit like a PS Audio, but I would at least get a heavy-duty Belkin or something. Also, if you've got your cable box hooked up to your stereo--either with a digital or stereo analogue cables--try connecting it instead with a TOSLINK (plastic fiber optic) cable. This will help isolate the cable box from your stereo system.

You might also consider getting a ground loop isolator. I was using an inexpensive unit I got in a car-stereo shop, and it seemed to work well.

If none of these things work, go to the hardware store and get a "cheater" plug (one of those 3-prong to 2-prong adapters). Even if your sub has a 2-prong plug, using a cheater plug sometimes helps for some reason. It's not an elegant solution, but sometimes it's the only thing that gets rid of the hum...

Good luck sorting this one out. A 60-cycle hum is almost always related to ground loop problems, and finding a solution can be one of the most maddening bits of trouble shooting you'll ever experience in the stereo world...

Welcome to to the forum, and hopefully we can help you get your system sounding great!

--Richard
Last edited by Dreamer on Thu Jan 01, 2009 10:36 pm, edited 1 time in total.
.....HT Rig • Sony STR-DG600 Receiver • Carver M-500t • Sony BDP-S1 • Sony DVP-NS3100ES • Apple Airport Express •
..............................• Martin Logan Scenarios, Logos • Realistic Minimus 7's • Velodyne F-1500b •

2 Ch. Rig • Carver C-4000t • Silver 7t's • Krell KAV-300i • Oppo DV-981HD • Benchmark DAC1-USB • MacBook Pro 17", iTunes •
......• Technics SL-1350 turntable with Sumiko headshell, leads, and Bluepoint cartridge • Martin Logan Sequels •

.........................................................-+-Click Here to see my system-+-
<<

aa7679

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Posts: 26

Joined: Thu Jan 01, 2009 11:36 am

Post Thu Jan 01, 2009 9:22 pm

Re: hum job

engtaz wrote:Welcome aa7679

Thanks , you guys have re ignited my passion for this sh*$
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aa7679

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Posts: 26

Joined: Thu Jan 01, 2009 11:36 am

Post Thu Jan 01, 2009 9:26 pm

Re: hum job

TNRabbit wrote:Teach it the WORDS, man!!

:D :D

Lol!!
<<

aa7679

Newbie

Posts: 26

Joined: Thu Jan 01, 2009 11:36 am

Post Thu Jan 01, 2009 9:30 pm

Re: hum job

Dreamer wrote:aa7679,

When I first got my Velodyne sb, I had a lot of problems with a 60-cycle hum too. It took me about a month of messing with it to figure out what was causing it. It turned out that it was related to my cable box--apparently cable systems are NOTORIOUS for creating ground loop problems when connected to a stereo system. My solution involved connecting the cable box to the receiver with an optical TOSLINK cable instead of the digital coax, AND putting a ground loop isolator between the outs of the receiver and the ins of the sub, AND putting the cable box and TV on their own surge protector, separate from the rest of the system. My sub would even hum if it wasn't hooked up to the receiver like yours, and in the end it was almost all about the power--NOT the cables, the componenets or the sub itself. Connecting the cable box to the receiver via digital coax introduced a little more hum to the sub AND made my main speakers hum too, but the sub's main hum was pretty much all caused by the power connection, when it was on the same circuit as the cable box and TV. Most AV gear, apparently, has a completely different kind of grounding topology than most stereo gear, and causes all sorts of problems...

I would suggest putting the sub on it's own separate power strip--get a good one with fast clamping and a high joule rating. It doesn't need to be a super-high-dollar unit like a PS Audio, but I would at least get a heavy-duty Belkin or something. Also, if you've got your cable box hooked up to your stereo--either with a digital or stereo analogue cables--try connecting it instead with a TOSLINK (plastic fiber optic) cable. This will help isolate the cable box from your stereo system.

You might also consider getting a ground loop isolator. I was using an inexpensive unit I got in a car-stereo shop, and it seemed to work well.

If none of these things work, go to the hardware store and get a "cheater" plug (one of those 3-prong to 2-prong adapters). Even if your sub has a 2-prong plug, using a cheater plug sometimes helps for some reason. It's not an elegant solution, but sometimes it's the only thing that gets rid of the hum...

Good luck sorting this one out. A 60-cycle hum is almost always related to ground loop problems, and finding a solution can be one of the most maddening bits of trouble shooting you'll ever experience in the stereo world...

Welcome to to the forum, and hopefully we can help you get your system sounding great!

--Richard
Dreamer wrote:aa7679,

When I first got my Velodyne sb, I had a lot of problems with a 60-cycle hum too. It took me about a month of messing with it to figure out what was causing it. It turned out that it was related to my cable box--apparently cable systems are NOTORIOUS for creating ground loop problems when connected to a stereo system. My solution involved connecting the cable box to the receiver with an optical TOSLINK cable instead of the digital coax, AND putting a ground loop isolator between the outs of the receiver and the ins of the sub, AND putting the cable box and TV on their own surge protector, separate from the rest of the system. My sub would even hum if it wasn't hooked up to the receiver like yours, and in the end it was almost all about the power--NOT the cables, the componenets or the sub itself. Connecting the cable box to the receiver via digital coax introduced a little more hum to the sub AND made my main speakers hum too, but the sub's main hum was pretty much all caused by the power connection, when it was on the same circuit as the cable box and TV. Most AV gear, apparently, has a completely different kind of grounding topology than most stereo gear, and causes all sorts of problems...

I would suggest putting the sub on it's own separate power strip--get a good one with fast clamping and a high joule rating. It doesn't need to be a super-high-dollar unit like a PS Audio, but I would at least get a heavy-duty Belkin or something. Also, if you've got your cable box hooked up to your stereo--either with a digital or stereo analogue cables--try connecting it instead with a TOSLINK (plastic fiber optic) cable. This will help isolate the cable box from your stereo system.

You might also consider getting a ground loop isolator. I was using an inexpensive unit I got in a car-stereo shop, and it seemed to work well.

If none of these things work, go to the hardware store and get a "cheater" plug (one of those 3-prong to 2-prong adapters). Even if your sub has a 2-prong plug, using a cheater plug sometimes helps for some reason. It's not an elegant solution, but sometimes it's the only thing that gets rid of the hum...

Good luck sorting this one out. A 60-cycle hum is almost always related to ground loop problems, and finding a solution can be one of the most maddening bits of trouble shooting you'll ever experience in the stereo world...

Welcome to to the forum, and hopefully we can help you get your system sounding great!

--Richard
Dreamer wrote:aa7679,

When I first got my Velodyne sb, I had a lot of problems with a 60-cycle hum too. It took me about a month of messing with it to figure out what was causing it. It turned out that it was related to my cable box--apparently cable systems are NOTORIOUS for creating ground loop problems when connected to a stereo system. My solution involved connecting the cable box to the receiver with an optical TOSLINK cable instead of the digital coax, AND putting a ground loop isolator between the outs of the receiver and the ins of the sub, AND putting the cable box and TV on their own surge protector, separate from the rest of the system. My sub would even hum if it wasn't hooked up to the receiver like yours, and in the end it was almost all about the power--NOT the cables, the componenets or the sub itself. Connecting the cable box to the receiver via digital coax introduced a little more hum to the sub AND made my main speakers hum too, but the sub's main hum was pretty much all caused by the power connection, when it was on the same circuit as the cable box and TV. Most AV gear, apparently, has a completely different kind of grounding topology than most stereo gear, and causes all sorts of problems...

I would suggest putting the sub on it's own separate power strip--get a good one with fast clamping and a high joule rating. It doesn't need to be a super-high-dollar unit like a PS Audio, but I would at least get a heavy-duty Belkin or something. Also, if you've got your cable box hooked up to your stereo--either with a digital or stereo analogue cables--try connecting it instead with a TOSLINK (plastic fiber optic) cable. This will help isolate the cable box from your stereo system.

You might also consider getting a ground loop isolator. I was using an inexpensive unit I got in a car-stereo shop, and it seemed to work well.

If none of these things work, go to the hardware store and get a "cheater" plug (one of those 3-prong to 2-prong adapters). Even if your sub has a 2-prong plug, using a cheater plug sometimes helps for some reason. It's not an elegant solution, but sometimes it's the only thing that gets rid of the hum...

Good luck sorting this one out. A 60-cycle hum is almost always related to ground loop problems, and finding a solution can be one of the most maddening bits of trouble shooting you'll ever experience in the stereo world...

Welcome to to the forum, and hopefully we can help you get your system sounding great!

--Richard
Dreamer wrote:aa7679,

When I first got my Velodyne sb, I had a lot of problems with a 60-cycle hum too. It took me about a month of messing with it to figure out what was causing it. It turned out that it was related to my cable box--apparently cable systems are NOTORIOUS for creating ground loop problems when connected to a stereo system. My solution involved connecting the cable box to the receiver with an optical TOSLINK cable instead of the digital coax, AND putting a ground loop isolator between the outs of the receiver and the ins of the sub, AND putting the cable box and TV on their own surge protector, separate from the rest of the system. My sub would even hum if it wasn't hooked up to the receiver like yours, and in the end it was almost all about the power--NOT the cables, the componenets or the sub itself. Connecting the cable box to the receiver via digital coax introduced a little more hum to the sub AND made my main speakers hum too, but the sub's main hum was pretty much all caused by the power connection, when it was on the same circuit as the cable box and TV. Most AV gear, apparently, has a completely different kind of grounding topology than most stereo gear, and causes all sorts of problems...

I would suggest putting the sub on it's own separate power strip--get a good one with fast clamping and a high joule rating. It doesn't need to be a super-high-dollar unit like a PS Audio, but I would at least get a heavy-duty Belkin or something. Also, if you've got your cable box hooked up to your stereo--either with a digital or stereo analogue cables--try connecting it instead with a TOSLINK (plastic fiber optic) cable. This will help isolate the cable box from your stereo system.

You might also consider getting a ground loop isolator. I was using an inexpensive unit I got in a car-stereo shop, and it seemed to work well.

If none of these things work, go to the hardware store and get a "cheater" plug (one of those 3-prong to 2-prong adapters). Even if your sub has a 2-prong plug, using a cheater plug sometimes helps for some reason. It's not an elegant solution, but sometimes it's the only thing that gets rid of the hum...

Good luck sorting this one out. A 60-cycle hum is almost always related to ground loop problems, and finding a solution can be one of the most maddening bits of trouble shooting you'll ever experience in the stereo world...

Welcome to to the forum, and hopefully we can help you get your system sounding great!

--Richard
Dreamer wrote:aa7679,

When I first got my Velodyne sb, I had a lot of problems with a 60-cycle hum too. It took me about a month of messing with it to figure out what was causing it. It turned out that it was related to my cable box--apparently cable systems are NOTORIOUS for creating ground loop problems when connected to a stereo system. My solution involved connecting the cable box to the receiver with an optical TOSLINK cable instead of the digital coax, AND putting a ground loop isolator between the outs of the receiver and the ins of the sub, AND putting the cable box and TV on their own surge protector, separate from the rest of the system. My sub would even hum if it wasn't hooked up to the receiver like yours, and in the end it was almost all about the power--NOT the cables, the componenets or the sub itself. Connecting the cable box to the receiver via digital coax introduced a little more hum to the sub AND made my main speakers hum too, but the sub's main hum was pretty much all caused by the power connection, when it was on the same circuit as the cable box and TV. Most AV gear, apparently, has a completely different kind of grounding topology than most stereo gear, and causes all sorts of problems...

I would suggest putting the sub on it's own separate power strip--get a good one with fast clamping and a high joule rating. It doesn't need to be a super-high-dollar unit like a PS Audio, but I would at least get a heavy-duty Belkin or something. Also, if you've got your cable box hooked up to your stereo--either with a digital or stereo analogue cables--try connecting it instead with a TOSLINK (plastic fiber optic) cable. This will help isolate the cable box from your stereo system.

You might also consider getting a ground loop isolator. I was using an inexpensive unit I got in a car-stereo shop, and it seemed to work well.

If none of these things work, go to the hardware store and get a "cheater" plug (one of those 3-prong to 2-prong adapters). Even if your sub has a 2-prong plug, using a cheater plug sometimes helps for some reason. It's not an elegant solution, but sometimes it's the only thing that gets rid of the hum...

Good luck sorting this one out. A 60-cycle hum is almost always related to ground loop problems, and finding a solution can be one of the most maddening bits of trouble shooting you'll ever experience in the stereo world...

Welcome to to the forum, and hopefully we can help you get your system sounding great!

--Richard
Dreamer wrote:aa7679,

When I first got my Velodyne sb, I had a lot of problems with a 60-cycle hum too. It took me about a month of messing with it to figure out what was causing it. It turned out that it was related to my cable box--apparently cable systems are NOTORIOUS for creating ground loop problems when connected to a stereo system. My solution involved connecting the cable box to the receiver with an optical TOSLINK cable instead of the digital coax, AND putting a ground loop isolator between the outs of the receiver and the ins of the sub, AND putting the cable box and TV on their own surge protector, separate from the rest of the system. My sub would even hum if it wasn't hooked up to the receiver like yours, and in the end it was almost all about the power--NOT the cables, the componenets or the sub itself. Connecting the cable box to the receiver via digital coax introduced a little more hum to the sub AND made my main speakers hum too, but the sub's main hum was pretty much all caused by the power connection, when it was on the same circuit as the cable box and TV. Most AV gear, apparently, has a completely different kind of grounding topology than most stereo gear, and causes all sorts of problems...

I would suggest putting the sub on it's own separate power strip--get a good one with fast clamping and a high joule rating. It doesn't need to be a super-high-dollar unit like a PS Audio, but I would at least get a heavy-duty Belkin or something. Also, if you've got your cable box hooked up to your stereo--either with a digital or stereo analogue cables--try connecting it instead with a TOSLINK (plastic fiber optic) cable. This will help isolate the cable box from your stereo system.

You might also consider getting a ground loop isolator. I was using an inexpensive unit I got in a car-stereo shop, and it seemed to work well.

If none of these things work, go to the hardware store and get a "cheater" plug (one of those 3-prong to 2-prong adapters). Even if your sub has a 2-prong plug, using a cheater plug sometimes helps for some reason. It's not an elegant solution, but sometimes it's the only thing that gets rid of the hum...

Good luck sorting this one out. A 60-cycle hum is almost always related to ground loop problems, and finding a solution can be one of the most maddening bits of trouble shooting you'll ever experience in the stereo world...

Welcome to to the forum, and hopefully we can help you get your system sounding great!

--Richard
Dreamer wrote:aa7679,

When I first got my Velodyne sb, I had a lot of problems with a 60-cycle hum too. It took me about a month of messing with it to figure out what was causing it. It turned out that it was related to my cable box--apparently cable systems are NOTORIOUS for creating ground loop problems when connected to a stereo system. My solution involved connecting the cable box to the receiver with an optical TOSLINK cable instead of the digital coax, AND putting a ground loop isolator between the outs of the receiver and the ins of the sub, AND putting the cable box and TV on their own surge protector, separate from the rest of the system. My sub would even hum if it wasn't hooked up to the receiver like yours, and in the end it was almost all about the power--NOT the cables, the componenets or the sub itself. Connecting the cable box to the receiver via digital coax introduced a little more hum to the sub AND made my main speakers hum too, but the sub's main hum was pretty much all caused by the power connection, when it was on the same circuit as the cable box and TV. Most AV gear, apparently, has a completely different kind of grounding topology than most stereo gear, and causes all sorts of problems...

I would suggest putting the sub on it's own separate power strip--get a good one with fast clamping and a high joule rating. It doesn't need to be a super-high-dollar unit like a PS Audio, but I would at least get a heavy-duty Belkin or something. Also, if you've got your cable box hooked up to your stereo--either with a digital or stereo analogue cables--try connecting it instead with a TOSLINK (plastic fiber optic) cable. This will help isolate the cable box from your stereo system.

You might also consider getting a ground loop isolator. I was using an inexpensive unit I got in a car-stereo shop, and it seemed to work well.

If none of these things work, go to the hardware store and get a "cheater" plug (one of those 3-prong to 2-prong adapters). Even if your sub has a 2-prong plug, using a cheater plug sometimes helps for some reason. It's not an elegant solution, but sometimes it's the only thing that gets rid of the hum...

Good luck sorting this one out. A 60-cycle hum is almost always related to ground loop problems, and finding a solution can be one of the most maddening bits of trouble shooting you'll ever experience in the stereo world...

Welcome to to the forum, and hopefully we can help you get your system sounding great!

--Richard
Dreamer wrote:aa7679,

When I first got my Velodyne sb, I had a lot of problems with a 60-cycle hum too. It took me about a month of messing with it to figure out what was causing it. It turned out that it was related to my cable box--apparently cable systems are NOTORIOUS for creating ground loop problems when connected to a stereo system. My solution involved connecting the cable box to the receiver with an optical TOSLINK cable instead of the digital coax, AND putting a ground loop isolator between the outs of the receiver and the ins of the sub, AND putting the cable box and TV on their own surge protector, separate from the rest of the system. My sub would even hum if it wasn't hooked up to the receiver like yours, and in the end it was almost all about the power--NOT the cables, the componenets or the sub itself. Connecting the cable box to the receiver via digital coax introduced a little more hum to the sub AND made my main speakers hum too, but the sub's main hum was pretty much all caused by the power connection, when it was on the same circuit as the cable box and TV. Most AV gear, apparently, has a completely different kind of grounding topology than most stereo gear, and causes all sorts of problems...

I would suggest putting the sub on it's own separate power strip--get a good one with fast clamping and a high joule rating. It doesn't need to be a super-high-dollar unit like a PS Audio, but I would at least get a heavy-duty Belkin or something. Also, if you've got your cable box hooked up to your stereo--either with a digital or stereo analogue cables--try connecting it instead with a TOSLINK (plastic fiber optic) cable. This will help isolate the cable box from your stereo system.

You might also consider getting a ground loop isolator. I was using an inexpensive unit I got in a car-stereo shop, and it seemed to work well.

If none of these things work, go to the hardware store and get a "cheater" plug (one of those 3-prong to 2-prong adapters). Even if your sub has a 2-prong plug, using a cheater plug sometimes helps for some reason. It's not an elegant solution, but sometimes it's the only thing that gets rid of the hum...

Good luck sorting this one out. A 60-cycle hum is almost always related to ground loop problems, and finding a solution can be one of the most maddening bits of trouble shooting you'll ever experience in the stereo world...

Welcome to to the forum, and hopefully we can help you get your system sounding great!

--Richard
TNRabbit wrote:Teach it the WORDS, man!!

:D :D

Very helpful. Ive got 2 input choices speaker level and rca.
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Dreamer

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SILVER-7t

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Joined: Mon Oct 30, 2006 1:17 am

Location: Washington, NC

Post Thu Jan 01, 2009 9:36 pm

Re: hum job

If your preamp/receiver has a separate RCA output and your sub is powered, use that connection--you'll have a LOT less to worry about as far as picking up any sort of interference on and RCA cable than you would with speaker-level cables, which are unshielded...

However, that said, I would NOT use a splitter on your pre-outs between pre and main amps if your pre does NOT have a separate sub output. I tried that, and there was NOTHING I could do to get rid of the hum in that setup, and it also injected some hum back into the line, so that it was coming out my mains too. There are few things more annoying that a 60-cycle hum coming out of big electrostatic panels (they cross over at 125 Hz)...
.....HT Rig • Sony STR-DG600 Receiver • Carver M-500t • Sony BDP-S1 • Sony DVP-NS3100ES • Apple Airport Express •
..............................• Martin Logan Scenarios, Logos • Realistic Minimus 7's • Velodyne F-1500b •

2 Ch. Rig • Carver C-4000t • Silver 7t's • Krell KAV-300i • Oppo DV-981HD • Benchmark DAC1-USB • MacBook Pro 17", iTunes •
......• Technics SL-1350 turntable with Sumiko headshell, leads, and Bluepoint cartridge • Martin Logan Sequels •

.........................................................-+-Click Here to see my system-+-
<<

aa7679

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Posts: 26

Joined: Thu Jan 01, 2009 11:36 am

Post Thu Jan 01, 2009 10:12 pm

Re: hum job

aa7679 wrote:
maddmaxxx wrote:-welcome to the Forum, mr aa !!!


-for me hum has generated from the patchcords [faulty grounds, communicating]


-iz the silent knight a lightstar unit ???, as ive heard of the darkstar, i think :-s

Thanks.

Carver Knight Shadow
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Dreamer

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SILVER-7t

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Joined: Mon Oct 30, 2006 1:17 am

Location: Washington, NC

Post Thu Jan 01, 2009 10:46 pm

Re: hum job

On a slightly related note, I've recently noticed a new sort of interferance in my sub. In the new house, the sub is behind the couch, and it's connected to the receiver via a LONG RCA interconnect (4 meters) which is actually 4 1-meter cables joined with gold-plated F-F connectors. The IC for the sub runs along the baseboard beside the couch where my sweetie sits, and when she's got her BlackJack phone on the arm of the couch, if someone calls or texts her, about 10 seconds before the call comes in, I can hear that unmistakable "digital hash" coming through the sub. It took me a few days to figure out where it was coming from--at first I thought it was her Dell laptop, but we ruled that out pretty quickly. My Apple iPhone doesn't cause this interference. Apparently the BlackJack is just a huge RFI broadcaster, and the incoming signal used to wake up the phone (or more appropriately, the outgoing "ping" that signals the cell switch that the phone is available) is a much higher-power signal than the signal for carrying a phone call. When she's actually on the phone, there is no interference...

I'm thinking that if I had a single long IC this would probably be reduced or eliminated. It's probably the F-F connectors that are picking up this digital signal, because they are those all-metal gold-plated RadioShack type of connectors. They are probably causing periodic leaks in the shielding of the cables due to their all-metal construction. I suppose I need to get online and go to Monoprice and order a long well-shielded subwoofer cable...

I was wondering if anyone else had run into this type of interference with long cables and close-by cell phones?

--Richard
.....HT Rig • Sony STR-DG600 Receiver • Carver M-500t • Sony BDP-S1 • Sony DVP-NS3100ES • Apple Airport Express •
..............................• Martin Logan Scenarios, Logos • Realistic Minimus 7's • Velodyne F-1500b •

2 Ch. Rig • Carver C-4000t • Silver 7t's • Krell KAV-300i • Oppo DV-981HD • Benchmark DAC1-USB • MacBook Pro 17", iTunes •
......• Technics SL-1350 turntable with Sumiko headshell, leads, and Bluepoint cartridge • Martin Logan Sequels •

.........................................................-+-Click Here to see my system-+-
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BillD

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Post Thu Jan 01, 2009 11:28 pm

Re: hum job

Yeah, you're probably picking it up on the shield at the connection points.
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
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aa7679

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Post Thu Jan 01, 2009 11:42 pm

Re: hum job

Dreamer wrote:On a slightly related note, I've recently noticed a new sort of interferance in my sub. In the new house, the sub is behind the couch, and it's connected to the receiver via a LONG RCA interconnect (4 meters) which is actually 4 1-meter cables joined with gold-plated F-F connectors. The IC for the sub runs along the baseboard beside the couch where my sweetie sits, and when she's got her BlackJack phone on the arm of the couch, if someone calls or texts her, about 10 seconds before the call comes in, I can hear that unmistakable "digital hash" coming through the sub. It took me a few days to figure out where it was coming from--at first I thought it was her Dell laptop, but we ruled that out pretty quickly. My Apple iPhone doesn't cause this interference. Apparently the BlackJack is just a huge RFI broadcaster, and the incoming signal used to wake up the phone (or more appropriately, the outgoing "ping" that signals the cell switch that the phone is available) is a much higher-power signal than the signal for carrying a phone call. When she's actually on the phone, there is no interference...

I'm thinking that if I had a single long IC this would probably be reduced or eliminated. It's probably the F-F connectors that are picking up this digital signal, because they are those all-metal gold-plated RadioShack type of connectors. They are probably causing periodic leaks in the shielding of the cables due to their all-metal construction. I suppose I need to get online and go to Monoprice and order a long well-shielded subwoofer cable...

I was wondering if anyone else had run into this type of interference with long cables and close-by cell phones?

--Richard

CB radios blast through my surround sound when trucks pass my house.
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OBI56

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Post Thu Jan 01, 2009 11:46 pm

Re: hum job

I had this problem Dreamer (2 RCA to RCA cables joined with gold plated couplers and some residual subwoofer hum) and solved it with a single 16 foot double twisted dual channel RCA to RCA dedicated subwoofer cable designed for this specific purpose. It also cleaned up a burst of interference that happened a split second before the wireless phone started ringing across the room, so sounds like a similar kind of problem.
Why let facts or common sense get in the way of your opinions.
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OBI56

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Post Thu Jan 01, 2009 11:49 pm

Re: hum job

aa7679 wrote:CB radios blast through my surround sound when trucks pass my house.


That is definitely a bad or missing ground somewhere. Been there, done that.
Why let facts or common sense get in the way of your opinions.
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Dreamer

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Post Thu Jan 01, 2009 11:55 pm

Re: hum job

aa7679 wrote:CB radios blast through my surround sound when trucks pass my house.


That, dear friend, is because you are probably using standard-issue "zip cord" type speaker cables for your rear surround speakers, which are acting like REALLY good antennae. If you'd used cables with a "twisted pair" or litz-braid topology, they would reject the CB radio interference. If your cables are accessable, you can disconnect them, "unzip" them, and then twiste them back together, with about a 3-twist-per-inch twist to them. Put some shrink wrap or electrical tape on them every few feet, and put them back in the rig. That should help a LOT, but really, if you're in a high-RFI environment, you need to use shielded speaker cables if you've got long (more than a few meters) runs, like for surround rears...

As we become an increasingly more "wireless" society with things like cell phones, wireless phones, wi-fi computer networks, and bluetooth devices, the issue of shielding is becoming more and more important. CB radios isn't something I've heard of causing RFI much though--I'd suggest those truckers are running some illegally amplified radios in their rigs if they are coming in over your stereo. I've heard of commercial AM radio and TV transmitters, and even HAM radios coming in over people's stereos, but never CB radios. CB's are relatively low-powered--I think the FCC limit on transmitter power for a mobile CB is still 5 or 10watts. I imagine some of those truckers have some hot little linear amps tucked away under their seats... 8-[
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OBI56

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Post Fri Jan 02, 2009 12:09 am

Re: hum job

3 twists per INCH Dreamer??? 3 twists per FOOT sounds more like it to me, but there are also 2 other tricks that can be tried before unzipping a pair of cables. One is to install a .01 microfarad ceramic disc capacitor across the amplifier speaker binding posts as suggested in the M-400t service manual and the second is to get some copper braid or metallized mylar tubing at your local electronics store and slip your speaker wires through that and ground it at 1 end. Used ot see CB radios interfering with stereo systems all the time 35 years ago when CB popularity exploded and those were the 3 tricks we used to resolve 99% of all interference cases back then (capacitor, copper braid, check all grounds). The only cases where none of these worked usually wound up being guys using high power transmitters piggybacked on their standard legal 4 watt maximum CD radios.
Last edited by OBI56 on Fri Jan 02, 2009 1:19 am, edited 1 time in total.
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maddmaxxx

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Post Fri Jan 02, 2009 1:16 am

Re: hum job

OBI56 wrote:3 twists per INCH Dreamer???



-cd radios ???






- 8)
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OBI56

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Post Fri Jan 02, 2009 1:20 am

Re: hum job

maddmaxxx wrote:
OBI56 wrote:3 twists per INCH Dreamer???


-cd radios ???

- 8)


Yeah Maxxx, you know what CDs are? Shiny round thingys that play music. Like you never make typos .... :lol: :lol: :lol:
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