Lots of cross referencing today between Audiogon and Audio Asylum. In any case, here's a link to a current thread that may work for you:
http://www.audioasylum.com/audio/general/messages/123338.html
Dave |
Well, I'm not giving up the TV. At least not until hockey season is over. ;-)
As for the RS fix, tried it and while the sound improved the picture quality was unacceptably poor. Eventually bought a ground isolator, but in this case even it is not enough. Thanks for the link in any case. |
Dear Fpeel,
Go to any MIT dealer and get the Iso-LinQ. This is an F to F cable with an EFFECTIVE (Richard Marsh designed)passive isolation device built in. This replaces the incoming link from your cable to the cable box. Use it BEFORE the TV cable interfaces with any component including the cable box. Much better than the Mondial.
Best of luck,
Joe |
Good detective work! I think if I were in your shoes, I'd suggest the cable co. attach their cable to a new dedicated ground, perhaps a few feet from your place? A new ground driven three or feet down and used strictly for the cable should decouple it from the rest of your electrical circuits. If that's not possible or practical, and you're using cable for the video content only, perhaps consider a satellite service such as DirectTV? ATB, Jeff |
fpeel: i'm not sure what you mean when you say you "put the tv and cable box in the loop," tho i assume you aren't plugging any cable leads into your sf l-1 (don't think it can be done, can it?). in any event, i agree with jeff that the most plausible problem is with the cable ground. i have my digital cable grounded into a copper rod well away from my electrical boxes; there are no common connections at all. i, likewise, have my telephone lines junction box and all associated wiring segregated from my electrical and coax. i have found an inexplicable reduction in what i assume was rf in my audio system when i recently replaced the cable box to tv coax with composite connections. i'm told that s video works even better but my cable box won't accept such outputs. i think you're on the right track. do check all splitters, too, and eliminate as many as you can. this will also enhance your video output. best of luck. -kelly |
I tried many ground loop isolators and NONE worked for DIGITAL cable. When it lifted the ground loop it interfered with the picture making it horrible or for some reason completely blocking it out. The solution was to use an stereo audio isolator made by Jensen Transformers. It is more expensive than their ground loop isolator but for DIGITAL cable it was the only way I could go. Works great. |
Cornfedboy: That phrase meant connecting the audio outputs of the TV to one of the inputs on the pre-. Sorry it wasn't clear. Thanks for the ideas, too.
To everyone: Went out today and looked even more closely at how the cable hook up is grounded. I was mistaken before and it isn't grounded to the main breaker box cabinet at my meter. It's grounded to MY NEIGHBOR'S main breaker box cabinet (we share a wiring closet). Of course, my neighbor's cable hookup is also part of this cluster, oops, can't use that word. But you get my drift.
Given that the manager at the cable company didn't call back with an update on getting a tech to come out as promised (big surprise there), I came close to changing the set up myself. Decided at the last minute to wait a day or so and see if they come through. Do you think moving the ground to my side of the electrical system would make much of a difference? My hunch is it won't hurt. It'd at least be a step toward isolating mine from the neighbor's. |
If floating the amp gets rid of the hum and does not tear up system performance, don't worry about it. I've seen and read more than a few manuals that specifically state that it might be necessary to eliminate / minimize multiple grounds. As such, ALL of your components are grounded if just ONE component is connected to ground.
Since most designs use a common ground, your interconnects tie all of the components ( and grounds ) together. As such, grounding your preamp and removing / reducing the other grounds seems to be the logical approach. Since ALL of the components ( sources, processors, amps, etc...) are all centrally tied into the pre, that is what you would want grounded. Then again, if they can do the installation "right" and let you keep your grounds, all the better. Sean
>
|
It sounds like your cable company is failing to comply with FCC guide lines, perhaps a reminder of this should be given to the cable company. |
Sean: That is pretty much my philosophy on the situation. I prefer to use the equipment as designed, but do want the best sound.
Given that the cable co. fails to fix the problem I am considering taking this to the extreme. Everything is plugged into a PLC except the amp. I have thought about floating the ground on it (and thus everything plugged into it). Then the amp would be the central gound point and the rest of the system grounded through it. Comments on whether this would be a good idea would be appreciated.
Of course, the $20,000 question is "Where does one buy a high grade cheater plug?"
Acas: That's what I said to the installer (admittedly out of frustration rather than actual knowledge), though it does seem they are in compliance with the National Electrical Code. It calls for the cable to be grounded at the entry point to the house. Unfortunately, the full text of the code is unavailable online except for a fee, so exactly what beyond that is required in as of yet an unknown. Any electricians out there that can help here? Thanks. |
Unless you have a digital power amp, i would ground everything BUT the amp. Some digital components such as CD's, DVD's, Transports & DAC's, maybe even tuner's, etc... are VERY ground senstive and get "squirrelly" when you remove ground. The good thing about this is that you already know that removing the ground from the amp itself takes care of the problem, so there is little guesswork on this one.
As to removing the ground from the amp, you can do several different things. My suggestion is to simply open up the IEC ( if it is screwed together ) on the amps' power cord and simply disconnect the ground wire. Before doing a "permanent" type modification, i would simply bend the wire back away from the terminal and wrap a layer or two of electrical tape around the bare wire. This will lift your ground, get rid of your hum / noise problem and still give you the benefits of what is called a "telescoping ground". This approach is FAR better than leaving ground connected at the IEC and lifting it at the wall outlet.
By leaving the ground wire connected at the IEC and using a cheater plug or lifting it inside the wall plug, the ground wire is still connected to the component. As such, you now have a long wire antenna connected to chassis ground. This opens the door to increased RFI or EMI based problems. While "cheating" the ground may have gotten rid of your initial hum / noise problem, you've now left yourself open to another form of "noise" and aggravation.
Most people don't think about this aspect of "lifting" ground and that's why i took the time to mention it. Sean
> |
Thanks, Sean. Your suggestion makes sense even to a non-techie like myself. Along that line, it would seem lifting the ground at the IEC inside the amp would accomplish the same thing. This is just me looking at options. The PC has heat shrink over the IEC that would have to be cut away, something I am reluctant to do. Not sure about the connection in the amp, but it may be easier to return to stock form than the PC. Is there a reason not to disconnect at the amps IEC? |
No reason at all not to disconnect inside the amp at the IEC and thanks for bringing that up. I forgot to mention it. I would caution that even though an amp might not be plugged in, you can still get "whacked" from the power supply reserve stored in the filter caps. As such, you can simply play some music and turn the amp off while maintaining a low to moderate volume setting. The amp will continue to play until the power supply is drained. It is then pretty safe to "poke around" inside the amp. Besides this, it will let you know just how good of a power supply reserve the amp has. Obviously, the longer the amp plays, the bigger ( & better ) the power supply reserve. Amps with relays in them will not do this, so don't worry if an amp of this type "dies" instantly when turned off. Sean
> |
Update: The tech from the cable company never called as promised. BUT he did visit. There is now a ground connection from the cable entry to my power meter's junction box instead of the former daisy chain to my neighbor's. Removing the cable ground isolator at the digital cable box and the cheater plug from the amp power cord as a check of the results showed there is a very minor hum audible only if I put my ear next to the speaker. This existed before and is a known system issue. It's better now than it was at the last house, albeit just barely so. Overall, an improvement. I also learned that the digital cable box has audio outputs. Using these is quieter than plugging into the back of the TV. Could be the age of the TV, could be a difference in ground potential. Either way it's quieter.
Thanks for all the ideas, guys. I'll most likely float the ground at the amp in one way or the other to create as low a noise floor as possible. Hopefully this discussion will serve as good reference for others having similar problems in the future. Again, thanks for helping sort this one out. |
