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just got my 3 dedicated outlets put in today. all done w/ 10g romex (which i had to fight the electrician for), using oyaide R1 outlets on all three lines. my system before the lines were putting in was dead silent. now, i've got a hum coming from the speakers when there is no music playing. what do i do?
Follow Ups:
as soon as i get home mid-next week i'm goin to check the polarity and will try to switch off the surge protector. i'm also going to move the equipment onto two receptacles instead of three. depending on what i find, i'll likely call the electrician back to have him move one of the outlets onto the other leg and possibly remove the surge protector if absolutely necessary. i honestly would like to keep it, if possible. it was a $300 surgeprotector for the unit... is that considered cheap?
Before you mess around with the surge protector (and I would not assume this is the problem), go through a step-by-step analysis to troubleshoot the problem and narrow down the likely cause.
If you have a TV cable or antenna, start there. Remove the cable or antenna from the cable box or TV and see if the hum stops.
Go through the troubleshooting analysis in the Jensen white paper:
I have Dedicated lines Never even thought twice about it when I built my House.. just did it.
My system is absolutely 100& dead quiet.. period.. tubes 'n all. I even use extension cords :-) with no ill effect.
Sometimes jumping on popular "bandwagons" just causes broken legs.
Hi.
How are the ground wires of the dedicated powerlines running from the breaker panels to the outlets. Are these ground wires ALL insulated?
How are the ground wires actually grounded???
Are these powerlines laid outside the wall or inside the wall?
The electrican who installed for you should be able to draw you the wiring schematic. I want to read it before Ican comment.
I DIY-installed myself a more comlex system: both 120V & 240V powerlines from the same fuse panel with dedicated ground wires, full insulated, with dedicated inline RF noise filters for digital & analouge gears repectively. Using audio grade cables instead of Romax types house wires.
No hum at all.
So somewhere along the line must be some wiring boo-boos.
c-J
Were you using multiple outlets to power your system before having the 3 dedicated outlets installed?
Were your components plugged into the outlets the same way that they are now (in the same configuration)?
Also, do you have to use more than one outlet to power your system? If not, it is usually recommended that you run from one outlet, as long as you don't pull too much current for one line. The idea is to minimize the number of potential pathways for ground loops.
I disagree about running all the equipment from a single outlet. Audio equipment power supplies pull non-sinusoidal current (typically short, steep pulses near the voltage waveform peaks). The impedance of the power circuit converts this current into a noise voltage, which is impressed upon all the other equipment on the circuit.
If the house wiring system permits, it is best to have a separate circuit for each piece of equipment. This gives better isolation of the power supplies than any power conditioner, and costs less in most cases.
The ground loop exists regardless of how many circuits. If a piece of equipment leaks to the AC ground, it should be repaired.
your opinion on a Bev Model III. Rick is currently working on mine and suggested I contact you. Thanks. Sam
:)
The bigger the loop, the bigger the problem. If you plug two three-pronged plug pieces of equipment into two different circuits, you've got potential for one BIG ground loop problem. There isn't always a ground loop problem. You shouldn't have a ground loop. You should connect equipment so there isn't a ground loop. The bigger the ground loop, the bigger the noise. Yes stuff will leak into the ground. You want that noise to not couple into the signal. Ground loops will garantee that it does. You put two monoblocks with three-pronged plugs on two separate circuits, and connect their grounded cases to each other via cable shields back to the preamp, and you got one huge ground loop back to the circuit breaker box instead of just the receptacle, which makes any ground loop even worse. Either way, you need to find some way to break the loop, and that may be by modifying the shield connections to enclosures or circuit boards.
See my reply below.
Hi AL, off topic here but i see you use the old beveridge system 3's I would like to talk to you about the beveridge speakers..
Lawrence
used-hifi@comcast.net
:)
Al,
I'm aware of your recommendations regarding multiple dedicated lines, and I don't know enough, myself, to determine if the your argument has more or less merit than those who advocate single receptacles if possible. I'm only aware of the various opinions because I've had hum problems myself and done quite a bit of searching here and elsewhere. One such source is the link provided by jea48, below, to the Jensen Transformers white paper. It states,
"...the voltage drops occurring in the safety ground wiring of the building are forced onto the audio cable shield system through the two or more safety ground connections. This problem will generally be made more severe as the distance (and length of intervening building safety ground wiring) increases. The worst case is two safety grounded devices operating from two different branch circuits of the building's AC power. The best case is two safety grounded devices located very near each other and operated from the same AC receptacle."
I realize the cited discussion is within the context of minimizing the potential for ground loop hum, and your point is about the noise induced by the equipment itself. All else equal, each point of view makes perfect sense. But, all else cannot be equal because the recommended courses of action conflict. Therefore, the solution is the one that leads to the least noise--of any kind--which means some type of compromise.
As for your statement about leaking to AC ground, the Jensen quote, above, seems to indicate that this is not the only possible source of ground loop hum related to safety ground. Your suggestion that the number of branch circuits being used is inconsequential appears to be in direct conflict with the statement by Jensen. Again, I don't know enough to argue one way or the other. What am I missing?
Louis
There are two ways to have a voltage drop along a safety conductor:
1. Induce an emf (electromotive force) with a strong alternating magnetic field; or
2. allow a significant leakage current to flow such that V = I*R, where I is the safety-earth leakage current and R is the resistance of the safety conductor.
Alternative 1. is possible in a theatre or a large office building, and probable in a factory. It is not likely in a domestic situation. I think the Jensen white paper author had a pro-audio situation in mind for this comment.
Alternative 2 implies a dangerously leaky appliance. A ground fault interrupter will trip if it is present on the circuit that feeds the leaky appliance, but many circuits do not have these devices. I would think such an appliance would make itself known fairly quickly by shocking someone, failing, or catching fire, so this is not likely to be encountered in the context of a mysterious hum problem.
I know how severe the power supply noise coupling effect is by experimenting with my own setup. I have four separate dedicated lines and presently three pieces of equipment. When I had four, I experimented with connecting a CD player and an InnerSound ESL-300 amp to one circuit. The sonic degradation compared to running each piece from its own circuit was substantial, and more than enough to justify the small added cost of the extra circuits to me.
To repeat, the use of multiple dedicated circuits reduces the power supply noise coupling effect as much or more than any single-input power conditioner can do. The offset voltages among the several dedicated ground conductors should be negligible unless you live in a factory. You are right that there are still trade-offs, however.
A ground loop may be silent in the audio band, but still can couple RF noise into an audio system. A tweak I've found effective is to place antiparallel diodes and low-resistance chokes in series with the ground leads to the equipment. Rectifier diodes have high impedance at low voltages, but can carry the fault current with a couple of volts of forward drop if necessary. They block low-level noise. The chokes add more impedance at higher frequencies, where the diode junction capacitance allows the noise to pass through.
It certainly does not take a strong magnetic field to induce noise in a ground loop! Ground loop hum is induced by a magnetic field, usually at low power supply frequencies. RFI is a capacitively coupled phenomena. Alternative 1 is certainly possible in the home. It is where hum comes from!
The Jensen paper is NOT limited to the pro environment!!!
Electrons don't the difference between pro and consumer gear! And your "tweak" of adding impedance in the ground loop is misguided. It is a bandaid approach, similar to a cheater plug, and probably dangerous or illegal. Any advice to purposely introduce impedance in the ground line should not be blindly followed. RFI is coupled into high impedences, and EMF into low impedance.
The fundamental cause of hum is a ground loop. Break the loop, and forget the tweak stuff. Also, use fundamental circuit techniques to prevent noise in ground loops from getting coupled into a circuit. (In a balanced circuit, your can have a ground loop through shields, but it is better prevented from being coupled into signal line, since the shield is not a signal line.)
I have been biting my tongue over many of your posts in the past, but have not bothered to argue with you because it would take more time to deal with than I care to use; and since, you have developed somewhat of a cult status due to your many posts, I felt that most of the newbies would blindly follow your advice, anyway. And I'm not going to continue arguing with you here. Unless you read and understand what information like the Jensen paper, Ott, Morrison, and other qualified people teach about noise and ground loops, then I don't think you have the fundamental background for preaching about this stuff.
You seem to know just enough about this topic to give highly dangerous advice. The only ways to break a ground loop are to lift the AC ground on one or more components, or install signal isolation transformers.
Lifting the ground removes the protection against a hot-to-exposed metal fault within the equipment and can kill someone. However, this risk is not immediately apparent in non-faulty equipment.
Installing isolation transformers requires construction skills, voids equipment warranties, and reduces resale values.
Guess which approach the uninformed audiophile will take.
You should use your precious time wisely, and think about how your words will be interpreted before you post them.
For your information, the Ebtech pro-audio device, that introduces antiparallel rectifier diodes into the AC ground, is UL-listed.
Al: ""
For your information, the Ebtech pro-audio device, that introduces antiparallel rectifier diodes into the AC ground, is UL-listed. ""
I can't find that on their site. I also don't see the device with UL printed on it. Where did this info come from? I would have figured they would blast that fact on the site, but I found nothing.
Al, your advice to use a low resistance choke in the ground path is indeed dangerous, and does not conform to code by itself. The impedance to ground cannot be such that it alters the clearing time of the breaker. I wouldn't want a fault which is supposed to be a magnetic clearing regime be dropped into the thermal regime..too slow.
NEC 250.4(B)(3) specifies a low impedance path for grounding, that may not occur with an unspecified choke..
I've used antiparallel diodes, but they MUST be capable of surviving intact at least 2 lobes (16 milliseconds) of 10 kiloamps. (by surviving intact, I mean, fail shorted without losing encapsulation integrity (blowed up).
Cheers, John
I haven't actually held one in my hands.
The choke I use is 10 microhenries and has a resistance of 0.006 ohms, essentially the resistance equivalent of an extra 2.4 feet of 14-gauge power cord. Larger inductance values do not sound as good.
The ebtech diodes are Taitron T6A10, 6 amperes at 100 volts maximum reverse-bias. My surplus bridges are supposedly 4 amperes at 400 volts, with two diodes in parallel in each direction the way I use them. They sound better than the Taitron. The larger the diodes's current rating and the smaller the reverse bias rating, the higher the junction capacitance and the less effective the tweak will be for blocking low-level RF noise. However, there is more to the sonic performance, as I've not found any stocked rectifiers of similar ratings that sound as good as my surplus devices.
Any unspecified tweak is dangerous. I expected that anyone seriously interested would ask for details.
Al: ""
I haven't actually held one in my hands.""
Nor I. You said it was UL listed, so I checked their site. They do not specify that anywhere I can find. So I was concerned that UL listing for the device may be incorrect. Do you have any information other than a privat e communication from a friend to show that it is indeed tested and listed by UL? I am suprised that the vendor would not advertise that fact if true.
Al: ""
The choke I use is 10 microhenries and has a resistance of 0.006 ohms, essentially the resistance equivalent of an extra 2.4 feet of 14-gauge power cord. Larger inductance values do not sound as good.""
The wire guage would have to actually be a large enough guage to support the specifications of a safety ground, you don't mention the guage of the choke windings. The problem of larger inductances of course, is, will it still allow enough fault current to trip the magnetic aspect of a breaker?
Al: ""
The ebtech diodes are Taitron T6A10, 6 amperes at 100 volts maximum reverse-bias. My surplus bridges are supposedly 4 amperes at 400 volts, with two diodes in parallel in each direction the way I use them. They sound better than the Taitron. The larger the diodes's current rating and the smaller the reverse bias rating, the higher the junction capacitance and the less effective the tweak will be for blocking low-level RF noise. However, there is more to the sonic performance, as I've not found any stocked rectifiers of similar ratings that sound as good as my surplus devices.""
The GI 1302 glass passivated Fast epi rectifier is rated 100 volts, 6 amps, 30 nanoseconds, with a vf of .925 at 6 amps. It's surge specification is ONE 150 amperes single half sine wave superimposed on rated load. A hard short within a house will run anywhere from 15 to 300 times the rating of the breaker prior to breaker clearing. This diode will not survive the short, and it is not guaranteed to retain package integrity either. In other words, it will shatter, and if it does so prior to the breaker clearing, you will be left with a hot chassis and absolutely NO safety ground.
If one chooses to use a safety ground at all (which should not be a decision at all...safety ground is a must), one should make sure that the components within the safety ground path are capable of performing their job.
Al: ""
Any unspecified tweak is dangerous. I expected that anyone seriously interested would ask for details. ""
One would hope that all would ask for details. But, if the device you mentioned is not UL approved for use in residential apps, and it cannot be counted on to fail short to force the breaker to clear the line, then how is the recommendation of the device any better than an unspecified tweak? The same with a choke, most will not know what is important with regard to the choke's specifications.
It is better to engineer the loop out, as well as the sensitivity to the loop.
Cheers, John
So how does Steve correct his ground loop problem?
Things we know so far.
#10-2 W/grd NM-B, (romex trade name), was installed for each of the three branch circuit wiring. Hard to believe there would be any resistance if measured at each recept between the neutral and equipment grounding conductor. Max allowed by NEC is one ohm.
All three circuits are fed from the same electrical panel and all three equipment grounding conductors are terminated in the same panel. How was the terminating of the three neutral conductors and equipment grounding conductors accomplished? we do not know. Are the neutral conductors and equipment grounding conductors terminated on the same Bar.In other words was the neutral bonded to ground in his electrical panel the branch circuits are fed from. This would have the neutral conductors and equipment grounding conductors terminated, sharing, the same neutral/grd bar.
Steve did not have a hum from his system before he connected his equipment to the three new dedicated circuits.
We know he uses a power conditioner.
We know that if he disconnects the ics from the preamp to the power amp/s the hum is not present. At this point we do not know if Steve tried the preamp and power amp/s tied together by the ics without any inputs of the preamp connected to any other equipment by ics. Ics removed.
----------------
What we do not know,
Are all three circuits connected to the same Line in the electrical panel.
What is the total length of each branch circuit.
Is the AC polarity of each recept correct. Hot and Neutral conductors not reversed at a recept.
What would happen if the power conditioner was taken out of the equation. Could it now be causing the problem.
Could a bad ic grd shield connection cause the problem. Corrosion maybe at the RCA jack or possibly the ic connector. Possibly poor contact or contact pressure.
-----------------------
What can be added to the list?
Al,
Thanks for taking the time to explain. It did sound as though the Jensen paper was geared toward pro audio to some extent.
I use only one receptacle on a dedicated line, but it feeds an ExactPower EP15A power conditioner/regulator/regenerator--not sure what to call it. It corrects the incoming waveform so that the power fed to the equipment is at a constant 120V and 60Hz. It has eight receptacles, but I'm not sure how they are wired to the internal circuitry.
If each of the four pairs is wired separately, then it seems like it would be approximately equivalent to having separate dedicated outlets as long as I stay within the limits of the unit, which is supposed to be able to handle a continuous 1500 watts. I only ever pull about 650-675 continuously, according to the EP15A readout. I suppose some dynamic swings may be truncated to some extent, but I don't notice, or feel the need for any more headroom--my room is not that large.
Louis
Two of the duplex outlets are labelled "digital AC outputs," and the other two are labelled "analog AC outputs."
I interpret this to mean there is passive filtering between the output of the regenerator (essentially, a high-powered audio amp delivering 120 volts at 60 Hz) and the "digital" outlets. This will keep much of the noise from the digital gear out of the equipment plugged in to the analog outlets.
You are correct that this device should take the place of separate dedicated AC lines, since it will have very low output impedance and reduce the conversion of equipment current waveforms into noise. To do this successfully, the feedback approach it uses should have very wide bandwidth. If it is band-limited in its feedback, it will allow cross-coupling of the higher frequency components of the equipment-generated noise.
I expect the safety-earth connections are continuous from the input through to all the outlets, regardless of how they are labelled. This means RF noise on the safety-earth will be shared among all the equipment pieces, and the ground loops created by the common safety-earth connections will remain intact. Being a species of audio amplifier, the EP-15A itself may generate RF noise and add it to the incoming noise and noise from the connected equipment.
Passive filters for reduction of EMI and RFI typically contain small capacitors that connect the hot and neutral to safety-earth. These capacitors have very high self-resonance frequencies, so they are effective at coupling RF noise from the hot and neutral to the safety-earth. The safety-earth is NOT a ground for RF noise, as the true connection to the earth is a long distance away in most cases. Thus, how much the EP-15A helps your audio system performance depends on where the major sources of RF noise are located, and their spectral composition.
i was using two receptacles. the balanced power unit (which powers my cd player, my preamp, my dvr, router, tv) and one monoblock on one receptacle, and the other monoblock on the other receptacle. i didn't know i should keep them on as few receptacles as possible. i think 2 20a dedicated circuits shoudl be enough for all that, yes?
I have a CDP, preamp (dual mono, two power supplies) and a pair of 140 watt tube monoblocks all plugged into an ExactPower EP15A, which is then plugged into one receptacle. I never draw much more than 5 amps, according to the readout on the EP15A.
The keys to whether or not you can use only one (versus 2) would be the power draw of the TV, and how large your monos are. The DVR and router likely have low power draws. You can add up the wattage (sometimes shown as VA) for all of the components and see if you approach 10 amps. If you get above 8-10 amps continuous, then you may want to go to a second outlet. My guess is that you won't be pulling more than 8 amps, but I could be wrong.
If I'm right, then plug your conditioner into one receptacle on one outlet, and plug your monos into the other receptacle on the same outlet via a good power strip. Or, go with Pooge's advice and use two outlets. Play around with the configuration.
Louis
Try plugging your monoblocks, and any other three pronged power cord, into the same receptacle.
My dedicated single 20amp line was installed during the building of the home. I am thinking about adding one or two more 20amp dedicated lines. If you do not mind sharing, I am curious as to how much each new line cost you...
Chris
awful expensive. i used a very well regarded electrician, becuase i wanted it done right. he charged 170 an hour + materials, total for 3 lines using 10gauge romex cost me about 2K. he charged travel time and lived about 45 min from me. anywho, he did a good job, at least cosmetically. he also installed some type of surge protector at the main breaker box.
...
charged $170 an hour!!!!!!
> > > > > > > > > > > > > > > > > > > > ....
After you have preformed the tests Al and I discussed I will have a few more for you to check.
Steve go buy a plug-in polarity checker, it will cost you less than $15 bucks.
Steve
You just found the hum...the surge protector at the box. Do you have hum on all your lines? Is it a house wide surge protector?
Alan
Turn off the 2pole breaker that feeds the surge protector.
okie dokie... i'll try that when i get back. he showed me the circuit box where he installed the lines, but i didn't see a breaker for the surge protector. i'll have to check when i get back. can't believe i might have to pay more on this project... lordy
Agreed...I think it's leaking too much to earth causing the hum.
Alan
Did the electrician install the 3 new branch circuit breakers on the same line in the electrical panel?
If you have a multi-meter set it to AC volts. Note the 2 straight blade slots in the receptacle. The smaller of the two is the hot conductor. Insert one test probe in the small slot of one of the dedicated circuit recept and install the other test lead in one of the other small slots of a recept of one of the other dedicated circuits. The reading should be o, no voltage. If it reads 240V nominal then the two dedicated circuits are not on the same line in the panel. One is on L1 the other on L2.... Repeat the process for the third dedicated circuit.
The electrician did terminate all 3 equipment grounding conductors wires in the same panel the circuits are feed from, correct?
the three lines are all terminated on the same panel, on the same side of the panel. when i unplugged all other equipment except for the amps, i still get the hum. when i unplug the interconnects from the amp though, the hum goes away. do i need to ground my preamp, or is something wrong w/my interconnects?
i'm scared to stick a volt meter into an outlet... is that dangerous?
> > i'm scared to stick a volt meter into an outlet... is that dangerous?
> > > > > > > > > > > > > > > > > >As long as you keep you hands away from the metal probes you will not get bit.....
If you feel safer shut off the 3 breakers. then insert the 2 test probes in to two different circuit recepts. turn back on the breakers and check for a reading on the meter....
Most electrical panels, not all.......
(1)L1 .......(2) L1
(3)L2 .......(4) L2
(5)L1 .......(6) L1
(7)L2 .......(8) L2
(9)L1 .......(10)L1
(11)L2 ......(12)L2
ect ......... ect
"All on the same side" does not necessarily mean on the same 120V leg. In an electrical panel, as you go down one side, the breakers are on alternate legs.
there are two lines on L1 and one line on L2.
again tho, when i disconnect the interconnects, but leave the amps on and connected to the speakers, the hum disappears...
Ground loop
can't friggin believe this. spent a boatload of money on dedicated lines and i get this?
i guess i could just not use that other dedicated outlet, right? plug everything into the two outlets on L1...
Call the electrician back to install all the lines to the same leg of the AC.
However, you should not have gotten hum even if one of the circuits was intalled to the other leg. Check all the outlets for correct wiring: hot (smaller slot) to ground should be 120 volts, neutral (larger slot) to ground should be zero volts.
Connecting your audio system to outlets wired to both AC legs increases its exposure to RF noise and degrades the purity of the sound, but, if all the neutral wires are installed correctly, you should not experience any audible hum. Something else appears to be wrong.
Al a reversed polarity at one of the recepts sure could cause his problem. Hard to believe the electrician would not have checked for proper polarity before he left the job though.
At any rate easy to check as you stated in your post. Steve is a little hesitant to use a meter on 120V. He could go to Home Depot and buy a cheap plug in polarity and equipment ground checker. That will tell him if the polarity is reversed on any recept.
away for the wkend, will have to troubleshoot next week. i'm ok using the volt meter on the recepticle, i'll just turn off those circuits before i do so, then turn them back on... basically i'm looking for a 0, right?
It sounds like the surge unit (cheap) is leaking on both the neutral and earth. If that it the case check for excessive leakage on the earth (the number one culprit for hum). I'm sure the polarity is fine. Unless the guy is a moran, it's pretty hard to screw up the polarity...especially for a pro who has done this more than once.
If it is the surge unit, there are three ways to fix it. One, rip out the surge unit and replace it with a quality magnetic breaker. Two, lift the ground at the outlet (not advised...but it is what the surge circuit believes you are going to do). Three, lift the ground by using either isolated or split phase (balanced) transformer on all your a/v circuits.
To clarify about lifting the ground at the outlet...if you have a copper cold water pipe near the a/v duplex, you could run a 12ga insulated ground to the pipe and have a good grounding set up. Take all of you dedicated lines and star ground them at the pipe clamp. Just make sure you scrub the pipe surface clean with Caig Progold 100% solution before installinth the ground. Also make sure the clamp is solid copper and not something cheap like zinc if you want a solid ground.
Alan
The notion of a separate ground for the audio circuits has been discussed before, but is worth repeating in this context.
The AC "ground" in USA-type wiring is a safety system. It is a separate conductor in each circuit that is tied to the neutral at the entrance panel. Its purpose is to carry fault current arising from a short from hot to exposed metal on the attached equipment until the circuit breaker opens, without allowing a lethal voltage to appear on the exposed metal. This means the resistance of the safety wiring has to be low.
By connecting the audio outlet ground terminal to a water pipe or other independent earth electrode, the safety circuit has the resistance of the earth between the independent electrode and the ground electrode to which the neutral is connected inserted into it. Fault current passing through this extra resistance could cause a lethal voltage to develop on the exposed metal of the faulty equipment and the circuit breaker might not even open. This could cause a fire.
The neutral and "ground" wires are all connected to earth at the service entrance to help protect against lightning-induced common-mode surges. If there should be a nearby lighting strike with a separate audio earth connection, the lateral currents that flow through the earth between the two electrodes can cause a very high voltage to develop between the neutral (tied to earth at the service entrance) and "ground" (tied to earth by the independent electrode) at the audio outlet. The outlet will flash over at about 6000 volts, but the equipment may be destroyed and set on fire in the process.
Agreed Al...which is why I told him not to pursue this option...instead I told him to lift the neutral using a isolation transformer.
Alan
One more clarification....the best option for you if you decide to keep the surge is to isolate your components with a transformer...either unbalanced or balanced is fine. This is the safest way to lift the neutral in order to stop the hum and remain grounded to the house.
Alan
It is not dangerous if you are careful, but I've always been wary.
When testing things like this, I get an extension cord or two, plug the voltmeter into the ends of the extension cord, then plug the extension cords into the wall.
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