Mallette Posted March 26, 2011 Share Posted March 26, 2011 Today I switched my big new plasma TV on for the first time whilst playing an LP. Major buzz... So, I checked grounding for the TT. The only way I can eliminate it is to ground to my body, which is inconvenient to say the least. No outlet or other equipment chassis seem to help at all. Any suggestions? If the two hundred pounds of sand in my TT base were in a sealed environment I'd add a bit of water and perhaps that would be adequate to simulate my body. I am sure the PAW would comment that it certainly would be analogous to my brain... To prove the point, that's about the only thought I've had other than leaving the monitor (it's for my media PC as well) off while playing discs. That will work, but I just hate not being able to make a hum go away. Dave Quote Link to comment Share on other sites More sharing options...
Marvel Posted March 26, 2011 Share Posted March 26, 2011 We just got cable at the house for the first time. MAJOR buzz through the 2A3 amps and LaScalas. Really a bum sound, but it's probably from the cable being in close proximity with the power coming from the street (150 ft. or so). The guy who installed the cable was like... I did my job. I swapped in my HK430 and I can barely, just barely hear it. The HK is no match for quality compared to the Moondogs, so I'm a little bit at a loss. I have plugged the DVD into the TV, and the digital cable into the TV, taking the audio out of the TV into the receiver. The TV has optical audio out, but all my gear is old school. I've found an optical to copper rca box, which would let me isolate the copper connex between the TV and the receiver. Bruce Quote Link to comment Share on other sites More sharing options...
cfelliot Posted March 27, 2011 Share Posted March 27, 2011 Similar problem! AC and cable have different ground potentials. Solution: Jensen Filter Quote Link to comment Share on other sites More sharing options...
Moderators dtel Posted March 27, 2011 Moderators Share Posted March 27, 2011 No outlet or other equipment chassis seem to help at all. Well that's strange, have your wife hold it and see if the hum stops, or does it just like you. [:|] Try hooking it up to a small antenna, I know it sounds crazy but for some reason your body will make most antenna pick up great, better than connecting to anything else. Does the two have any connection with each other, probably not, but I don't know if it's the moisture in your body/skin or whatever causes it, but it's doing something. Quote Link to comment Share on other sites More sharing options...
Marvel Posted March 27, 2011 Share Posted March 27, 2011 Well that's strange, have your wife hold it and see if the hum stops... What were you thinking? Bruce Quote Link to comment Share on other sites More sharing options...
Moderators dtel Posted March 27, 2011 Moderators Share Posted March 27, 2011 Well that's strange, have your wife hold it and see if the hum stops... What were you thinking? Bruce Well that does sound a little strange, now that I look back. Quote Link to comment Share on other sites More sharing options...
pauln Posted March 27, 2011 Share Posted March 27, 2011 The question may be backwards and the comment above about the body being a great antenna more accurate. We guitar players notice this all the time and usually think we are grounding the strings by touching them to make them quiet. See this link for the current theory (bad pun) which looks at it the other way. Here Now about the cable. The line into my home goes to a splitter in the attic from which it projects and drops down into the walls in about four different places, only one of which I use. I noticed that when I played my guitar and stood anywhere near one wall with one of the unused cable outlets I got noise. I disconnected all but the one I use from the splitter and the noise disappeared. Dave, there is something you can try. Disconnect each component and measure AC volts with a multimeter between the chassis and the outlet ground screw while the component is powered on. Then reverse the orientation of the plug in the outlet and repeat the measurement, using a cheater plug if the component is a three prong plug or one of the modern ones where one blade is wider than the other. You will get two different AC volt "leakage" readings, one higher than the other like 30mv and 80mv. Mark the plug for the orientation that has the least AC volts. Repeat with each component, then plug them all in with the lower volt orientation. This gives you the lowest noise floor as a baseline for any further ground hum or noise issues to be solved. For any components using the cheater to get this orientation, just run a wire from the component chassis to the ground screw on the outlet face - it is the same as the ground hole in a three hole outlet, which is just a redundant safety ground identical to the neutral slot. Or use the cheaters that accept the three prong on one side and present a ground wire on the other to connect to the ground screw... I'm sure you already know most of this stuff above. The reason plug orientation shows an imbalance is that the power supply from the utility has a "single ended" aspect to it. The two AC 110V wires from the pole to the home are out of phase. Both are used together for 220V outlets. For 110V outlets only one of those is used and it goes to the "hot" slot in the outlet face. The "neutral" slot just goes to the ground in the breaker box. So does the "ground" hole in the outlet face. The single ended thing comes in because you are placing your component's power supply between the AC 110V "hot" slot and the grounded "neutral" slot. The convention for fused power supplies is to place the fuse on the "hot" side of the transformer primary coil, but not all manufacturers do that. Hope you get things worked out. Quote Link to comment Share on other sites More sharing options...
Brac Posted March 27, 2011 Share Posted March 27, 2011 Good Info, I'll try it out some time. Quote Link to comment Share on other sites More sharing options...
Mallette Posted March 27, 2011 Author Share Posted March 27, 2011 Paul, I'll check into this and all as I have time. However, I rechecked my original post and many seemed to have miss what I said. Cable, an LCD TV, and all have been hooked up without a major issue for 6 years. What changed is a plasma TV. My assumption is we are talking RF or EMF here. Of course, if I really had the answer I wouldn't have posed the question. As to having the PAW hold it, we've tried that many times in the past with varied results... [:#] Dave Quote Link to comment Share on other sites More sharing options...
Guest " " Posted March 27, 2011 Share Posted March 27, 2011 maybe you need one of these. it's basically a virtual cheater plug when there is no ground faults conditions and an active ground when there is. You just have to make sure that the diodes are rated for the circut breaker amp current. How does it work. When there is no grounds faults, it's a cheater plug becuase the forward voltage drop rating of the diode is higher than the voltage to ground drift when everything is normal. Once a ground fault condition occurs, the voltage potential to ground becomes higher than the forward voltage drop of the diodes, and the diodes turn on, allowing the condition o short to ground. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted March 27, 2011 Share Posted March 27, 2011 maybe you need one of these. it's basically a virtual cheater plug when there is no ground faults conditions and an active ground when there is. You just have to make sure that the diodes are rated for the circut breaker amp current. How does it work. When there is no grounds faults, it's a cheater plug becuase the forward voltage drop rating of the diode is higher than the voltage to ground drift when everything is normal. Once a ground fault condition occurs, the voltage potential to ground becomes higher than the forward voltage drop of the diodes, and the diodes turn on, allowing the condition to short to ground. Quote Link to comment Share on other sites More sharing options...
Marvel Posted March 27, 2011 Share Posted March 27, 2011 I have 1.3 VAC between the shield and ground on teh RG59. Bigtime hum... Bruce Quote Link to comment Share on other sites More sharing options...
pauln Posted March 27, 2011 Share Posted March 27, 2011 RG59? What are you using it for? When should I use RG59 versus RG6 Quote Link to comment Share on other sites More sharing options...
Mallette Posted March 27, 2011 Author Share Posted March 27, 2011 In reviewing this, basically the usual suspects... Remember, this only comes into play when the TV is switched on, and the previous LED TV did not do it. I remain convinced the plasma is created a strong EMF field. The fact my body serves as a sink for this suggests it should be possible...not using meat products...to construct something to handle it. I am going to stick a humbucker I have in the phono lines but I have concerns about using it in a phono level line as oppose to line level, both sound impact as well as doubts as to its efficacy. However, might as well try it. I also have a Jensen filter on hand but can't see what the cable would have to do with it as that's going into the sat box and is never near the TV. I suppose I can just throw a long line over to the sweet spot and wrap it around my arm... Not a satisfying solution, and I don't think my son will lay on the floor and play ground for me. Dave Quote Link to comment Share on other sites More sharing options...
Marvel Posted March 27, 2011 Share Posted March 27, 2011 RG59? What are you using it for? When should I use RG59 versus RG6 Well... my bad. It is RG6. Comcast (for good or ill, but we have a much faster internet connection now, compared to the DSL we had. We get 24-30 Mbit download speeds and 6 up. Bruce Quote Link to comment Share on other sites More sharing options...
Don Richard Posted March 28, 2011 Share Posted March 28, 2011 The two AC 110V wires from the pole to the home are out of phase. Both are used together for 220V outlets Then they would not be out of phase then, would they? The xformer on the pole is center tapped and connected to earth. with 120VAC on either side of the center tap. When used together they form a single phase balanced 240VAC power source. Quote Link to comment Share on other sites More sharing options...
Chris A Posted March 28, 2011 Share Posted March 28, 2011 Today I switched my big new plasma TV on for the first time whilst playing an LP. Major buzz... So, I checked grounding for the TT. The only way I can eliminate it is to ground to my body, which is inconvenient to say the least...No outlet or other equipment chassis seem to help at all...Any suggestions?You could convert to a balanced connection (if you haven't already done so...). This will definitely address common mode buzz. What kind of phono preamp connection do you presently use?Another discussion on balanced connections. Yet another approach is to minimize the low-signal cable span by mounting your TT preamp inside the TT plinth--if the preamp is small enough and your TT plinth is large enough. In fact, I wonder why this isn't done as SOP. It would also be nice if TT plinths were made out of conductive material to form a Faraday cage: EMI standard design practice is to "seal up the holes". Chris Quote Link to comment Share on other sites More sharing options...
Chris A Posted March 29, 2011 Share Posted March 29, 2011 One thing that I've found to be effective is to simply twist the wires an extra amount (like 1 turn/foot) to further reject EMI-induced buzz--but you probably already know that. Also, if you are a "neatness fanatic", I'd say that routing your TV and phono cables away from one another and making sure that they are not parallel to each other will help out. This is one place where messiness is actually desirable: in routing cables. My old man used to make a big deal of this when I was young when he was consulting in industrial electronics design. I've never forgotten that lesson since I got to spend time watching frustrated design engineers learn that lesson the hard way. I should mention that all the info on this subject I've encountered indicates that the buzz you hear is caused from not using balanced connections - and the result is induced ground loops, especially for cases where you've got a big E/M emitter like your TV. I do not see how you will suppress its emissions. I separate my old Empire 398 TT (using the original cable and an external phono preamp) from my LCD TV by the widest dimensions that I possibly can - my electronics rack is off to the left side of the setup and the TT is further back on the left. I set the TT on top of one surround CW (never plays in 2-channel mode). It's a stable and quiet position, and at just the right height to cue the lead-in groove. Chris Quote Link to comment Share on other sites More sharing options...
Mallette Posted March 29, 2011 Author Share Posted March 29, 2011 Well, I may need to see if it's possible to relocate my phono preamp to the TT table. It's problematic as my primary phono stage (I have a second for 78's) is located in my Super PAS4i preamp and about a six foot run from the TT. Don't need to tell me that is an issue, though it was pretty minimal until the TV switch out. I didn't build my TT base with anything other than my two TT's in mind, so I am not sure I can work it out. My 78 phono stage is a small box that is behind one of the TT's. I suppose I could switch my LP TT to it to see what the effect is of having a six foot line level run to the preamp rather than the same as a phono stage. The humbucker would work OK with that. It's a good one and I've found it to eliminate hum in line level applications without impacting the sound. Dave Quote Link to comment Share on other sites More sharing options...
Guest " " Posted March 29, 2011 Share Posted March 29, 2011 them term phase is confusing when an audio person is talking to an electrical person. When an audio person says the legs on a 220 run are out of phase, one sees +110 on one end and -110 on the other. When connected across, we see 220. The transformer changes the deferential ground making the center tap the new ground. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.