Why is a 1.5-2 volt AC signal on my Neutral line?


I have several music sources e.g. DVD, Phono, DAC, Tuner etc...

I just purchased a NAIM integrated amp and I am experiencing a hum but only from the DVD player.

I have circuit tested the entire house wiring and all is well.

After a lot of investigation I found that some units have a 1.5-2.0 volt AC signal (sounds like a 60Hz signal i.e. hum) between the neutral side of the interconnect and the earth at the power bar.

Panasonic, Pioneer and Sony units I have measured all have this signal present and it varies between 1.5 - 2.0 volts

Luxman and Cambridge Audio gear does NOT have the signal present

All units have a polarized plug with no ground pin

How can the hum be eliminated using the Pioneer DVD with the NAIM Amp?

Thanks
williewonka

I assume the NAIM has a three prong plug? If so, what happens if you lift the safety ground on it?
I just purchased a NAIM integrated amp and I am experiencing a hum but only from the DVD player.

DVD player connected to a TV?
TV connected to CATV?

Disconnect the incoming CATV coax from the CATV box then check for hum.
If no hum..... Buy a Jensen ISO transformer....
Lifting the ground makes the amp hum more

This is a "Stereo" setup only - amp tuner, DVD(i.e. CD) and PHONO - no TV/AV components or connection to cable equipment.

Thanks for the info though - I'll tuck that away for future use
If I understand your post correctly, it sounds to me like you've got a defective interconnect (or two) somewhere.

I think you are saying that with ALL of these components simultaneously connected into the system, if you connect your meter between the ground sleeves of various rca connectors and safety ground on the power strip, in some cases you see a substantial voltage and in some cases you do not.

If that is the correct interpretation, it would seem to say that a cable somewhere is not properly tying the grounds of the connected components together.

Regards,
-- Al
Water your service ground.

or, re-establish a better connection where the ground lug attaches to the ground rod. IOW... take it off and clean it up... then reattach it. This might also be a good thing inside the service panel to do.

An inductor on the neutral line might also help. you can make one by using some #14 or even #12 solid wire by making 10 to 20 loops tightly wrapping from palm to elbow, round and round again, and then using some tape to keep the loops together... open the receptacle and splice in the DIY inductor on the neutral side with a pr of wire nuts.

The more loops, the greater the effect.

There's a difference of potential and I suspect as Al said a poor connection, though in either the breaker box in the home or at the service panel outside on the power pole.

naturally, swapping out the ICs is the easiest thing to do first.

The netral bus bar and ground are tied together in some areas of the country too and loose bars or connections might cause such a thing too. As could plain old corrosion and loosening of the screws on the bus bars themselves.

...and/or in the outlets.

good luck.
After a lot of investigation I found that some units have a 1.5-2.0 volt AC signal (sounds like a 60Hz signal i.e. hum) between the neutral side of the interconnect and the earth at the power bar.
Williewonka 06-24-10:
between the neutral side of the interconnect and the earth at the power bar.
Williewonka,

Not sure what test you preformed.... Can you be more specific. What do you mean by "neutral side of the interconnect"?

Lifting the ground makes the amp hum more
06-25-10: Williewonka
Are you sure the sound you are hearing is a hum and not a buzz. Does the noise vary when changing the volume level?

I just purchased a NAIM integrated amp and I am experiencing a hum but only from the DVD player.
06-24-10: Williewonka
I would try what Al said in his post. Could be a bad interconnect. Could be a bad signal ground solder connection inside the DVD player.
Does the hum/buzz change if you put your hand on the metal case of the DVD player?

I would also try another set of line-input jacks on the NAIM.
I recommend buying 2 RCA to RCA Test Adaptors with Troubleshooting Guide from Jensen Transformers.

Using the adapters and following the guide will tell you exactly where your problem is located, and whether it's caused by electronics or wire.

Blindjim

Water your service ground.

Service ground has absolutely no relevance at all.
Simply_q

it'll sure tell you if there is a weak connection there.

it's certain there's a weak connection, or resistive connection somewhere , if not in one of the devices, then it has to be in the service.

I'm figuring the house is older than the equipment and felt to start from the begining ... at the service pole and follow it back to the outlets being used. Skipping around looking at this or that seldom plays out well.

I've seen far wierder stuff happen.

Blindjim

it'll sure tell you if there is a weak connection there.

No it won't. The ground road has nothing to do with your audio system or with any ground loop noise in your audio system.

Oops. Meant to say ground rod, not ground road.
Blindjim,

A difference of potential, voltage, measured at an electrical outlet measured from the neutral to the equipment grounding conductor can be the result of VD, voltage drop, on the loaded neutral conductor. If the resistance of the equipment grounding conductor is less than the resistance of the loaded neutral conductor then there can and will be a difference of potential between the two conductors.

VD is directly proportional to the size, length, and load placed on the conductor.
Poor connections along the length of the conductor can cause higher resistance in conjunction to the amount of load placed on the branch circuit neutral as well.

As Simply_q said in his post the main service earth ground connection does not come into play. In most cases the branch circuit neutral conductor as well as the branch circuit safety equipment grounding conductor terminate on the same neutral/ground bar in the main electrical service panel.... Sub panels will have them separated on two different bars but they still end up tied together at the main service electrical panel via the feeder neutral conductor and equipment grounding conductor. Both connect together at the main panel.


Jea48

“most cases the branch circuit neutral conductor as well as the branch circuit safety equipment grounding conductor terminate on the same neutral/ground bar in the main electrical service panel.... Sub panels will have them separated on two different bars but they still end up tied together at the main service electrical panel via the feeder neutral conductor and equipment grounding conductor. Both connect together at the main panel.”

Yeah… I know… I said that already. See above. I’ve installed services for both industrial and residential… for years. Years ago.

The OP said this issue happened right after he added another (new?) amp.

Things were ok BEFORE I GUESS.

So one should always look at the last thing (s) which were altered or changed, to find the answer for a problem…. If indeed a problem came as the result of that change. Apparently there is/was an issue following the amps addition to the system.

I had a similar incident a few years back when I added a near new amp, and thereafter a brand new amp. Two in fact. The ‘hum’ I experienced was attributed to the grounding system in my home. Not the amp (s).

Consequently I said what I said for a reason. Maybe we ought to call Ripley’s Believe it or not’, here.

Ultimately I had to lift the ground from the dedicated ckt (s) driving the amp (s). Further, I had to also mitigate the CATV connection to the service ground by use of a transformer as mentioned above, as BOTH ITEMS introduced issues to the system. Even though as the OP said too, my CATV was not connected to my then stereo system.

It is however connected somewhere else.

It was connected to the service ground at the power pole, and et al, above… everything gets tied together there… neutrals and commons.

Sometimes an issue has one thing causing the problem, sometimes it’s predominately one thing that makes you notice it, but sometimes there are also other contributing factors which only raise their heads once the issue is reailized.

The CATV connection outside shouldn’t have matter possibly but it did.

In some areas around here some counties make new construction employ two different ground rods. There’s always the risk then of acquiring a difference of potential there. In sandy conditions drainage is severe, reducing the actual ground rod conduction with the earth itself. Rods longer than the eight foot norm would work better perhaps, but I’ve seen the value of keeping that area surrounding the rod damp or wet. Especially in times of extended drought or no rainfall.

Sometimes electrical issues defie practical or common sense approaches. So I tend to keep a more open mind and not merely stick strickly to imperical wisdom.

When the electrical contractor I worked for got the contract to build the local Honeywell location, we ran across a problem with numerous ground rods and a variety of ckts. All the rods were in one common area. All solid copper. All 10 or 12 ft long. Some of the ckts wound up with hums. Front to back several times we went thru the ckts finding nothing out of the ordinary. By then the surrounding area had been poured and there was no way to remove the rods … only to relocate them. Instead of reworking all the rods with another install, someone, one of the older sparkys came up with the DIY inductor.

We all had a good laugh at his expense when he told us about it. BUT it worked fine after a few tries. I don’t think anyone ever told Honeywell what we actually did to fix the situation though.

So I don’t just make this stuff up. Believe it or not.

Regardless, I hope things get figured out… one way or another.
You have a ground loop issue. Neutral is grounded at the main electrical panel box however the length of cables and a poor contact somewhere (or a cheater plug) to the equipment can allow a small stray voltage to build up from some power supply leakage to ground (coudl be a faulty component). An RC interconnect will provide the return for a small stray current and hence you will induce a hum in the line level signal. With RCA you always have this problem to a greater or lesser degree - although the hiss or hum may often be low enough not to be of significance in a system with low dynamic range.
Guys, I think we need clarification from the op, as I implied in my earlier post and as Jim requested. My suspicion is that the reference to 1.5 to 2.0 vac on the "neutral line," on some components only(!), does NOT refer to the ac neutral.

For one thing, he referred to "the neutral side of the interconnect." Also, how would he be able to measure the voltage between ac neutral and ac safety ground individually for each component, without opening it up and probing internally under the chassis?

So as I indicated in my earlier post, I suspect he is referring to an ac voltage between circuit ground (as measured on the ground sleeves of rca connections) and ac safety ground. As Jim and I indicated earlier, if he is seeing a significant difference among those readings for different components, while the components are interconnected, he's either got a defective interconnect or a defective circuit ground connection on one or more of the rca jacks. Either of which could certainly account for a hum problem.

Best regards,
-- Al
I gave a complex answer. Here are a few simple solutions.

If the NAIM has an optical in then try that.

Disconnect the video to the TV and see if the hum goes away - if it does then check your TV is grounded properly (no cheater plug).

Whatever you do - do NOT use cheater plugs on the Naim or on the TV - this can expose you to dangerous voltages in the event of an equipment failure.

Shadorne

Whatever you do - do NOT use cheater plugs on the Naim or on the TV - this can expose you to dangerous voltages in the event of an equipment failure.

I don't recommend using them as a long term solution, but they're perfectly fine for troubleshooting.
You also need to measure the RCA neutral to the case of the
equipment for voltage difference.If it there,that could be inductive pickup from the case housing the transformer, especially in a power amp with a big transformer.If the difference is between the neutral and ground at the outlet, that just may be the load on the feeder causing a voltage difference.This may be normal when there is a load
on it.Like mentioned above,clarification is needed.The power bar may be all metal,and tied to the outlet ground.
I go with the more clarification needed also.
Thanks all for the feedback - just to clarify the situation

The house is 23 years old and the supply comes in from the street via a subterranean cable.

The breaker box is earthed to the water supply pipe - and I could not detect any grounding problems at the breaker box or anywhere else in the house - I have verified there are no spurious voltages between neutral and ground anywhere in the house (tested with a very good digital meter for resistance, continuity, AC and DC Voltage) - particularly at the outlets with appliance connected - BTW all appliances are new this year - so no old lunkers are causing problems.

I also tested the equipment with only the dedicated line to the hi-fi turned on - YES - I took all of the other breakers offline.

Each piece of equipment (has a two pin polarized plug) was tested without connecting it to the amp and found that Sony, Panasonic, Pioneer and Toshiba all had a 1.5-2.0v AC voltage between neutral of each phono socket (and also the chassis) and the ground of the outlet they were plugged into - I also verified that the outlet did not have any spurious voltage present before plugging in the equipment - However on testing the Cambridge Audio sources and the Luxman sources I found they did not produce any voltage between their phono neutral or chassis - so they work well with the amp.

I have spoken to NAIM tech support and they indicated that their design philosophy is somewhat different from that of the consumer electronics manufacturers and that difference results in a hum when used with them.

Their solution is to use a ground loop isolation device which are commonly available, between the amp and DVD player.

I would guess that other hi-fi oriented manufacturers adopt a different design philosophy that allows consumer electronics to be connected without a problem, because I have not found too much on this topic - other than the normal ground loop problems due to bad cabling/mains/ground etc...
other than the normal ground loop problems due to bad cabling/mains/ground etc...

Yep other than the normal problems from using RCA.

Please understand that stray voltages ALWAYS exist but for the majority of cases the micro-currents are small enough so that they do not induce much audible hum as they circulate through your interconnects. The only proper solution is balanced - invented ages ago - but the desire by manufacturers to reduce cost means you often get RCA - even on expensive components.
I second Shadorne's comments.

So it sounds like you are saying that the 1.5 to 2.0 vac that you measured was between the circuit ground/chassis ground of each component and ac safety ground, WHILE THE COMPONENT WAS NOT CONNECTED TO ANY OTHER COMPONENT. Given that, what you were seeing was simply the voltage to which the component's circuit and chassis grounds (which are usually common) "float" in the absence of a direct connection to ac safety ground (such as via an interconnect to another component which in turn has a 3-prong power plug).

That level is typically determined by the happenstance of stray capacitances within the component between circuit ground/chassis ground and each of the two sides of the incoming ac line ("hot" and "neutral"). The most significant stray capacitances are usually in the power transformer. Sometimes intentionally present capacitors and/or stray resistance paths may also be significant.

A good quality ground isolator, such as those offered by Jensen Transformers, should solve the problem. Also see this paper at their site.

Regards,
-- Al
You have a ground loop problem between one or more units. Also if you have a separate line and breaker but use the same ground at the box, it is all still connected together. If you know this please forgive me but you must drive a new ground rod at least 8 feet away from the other ground or where the water pipe goes into the ground. This could be shorter or longer away depending on the soil; hard or soft - wet or dry, etc.! Back to the ground loop. Disconnect one unit at the time until the hum is gone. That is the one that has the difference of potential. Sometimes you can connect a wire between the two units, under chassis screws and solve the problem and sometimes you have to sell the problem and get something else. Ground loops are one of the hardest problems to fix. There is another way to fix or at least remove the noise but it takes a lot more electronic work. However, like said too already one of your rca's could have lost it's ground. With locking RCA's this happenings a lot more because the IC is pulled or heavy maybe and breaks the cheap little pin and hum! It does not matter if you are using that RCA's or not because the broken ground acts like a antenna for noise. Good luck!
I tried all the steps provided by several contributors above.

Only the Jensen RCA test adapters allowed me to identify the problem area. They cost $12.00/pair.

I reiterate my recommendation to buy them. It will save you time.
Hum Gone!

I bought a ground loop isolator by Behringer - it is exceptional since there is negligeable signal loss and the signal quality is maintained

I understand the Jensen product is also very good

Thanks for the input
UPDATE: turns out NAIM only ties the neutral side to the ground in their source components - not at the amp.

The Ground Loop isolator mentioned above eliminated the additional hum introduced by the Pioneer DVD player.

But when I connected the "Ground" screw on the Phono stage to the ground screw on the power conditioner an eerie silence came over the entire system

The manual for the phono stage does not indicate whether this is good or bad practice, but it works and I did not have to mess with grounding component chassis - just used the terminals available.

Anyhow - all is now quiet - just very pure music - I even removed the ground loop isolator.
I am glad that we were able to pinpoint the problem as being due to a Ground Loop and help you solve it!
UPDATE: turns out NAIM only ties the neutral side to the ground in their source components - not at the amp.
07-07-10: Williewonka

Williewonka,

?? Your use of the word neutral is confusing....
From reading your posts I believe you use the word neutral in reference to the outer shell of the RCA jack, the signal ground.

Are you saying on your NAIM amp the signal ground is not connected to the chassis? The chassis is only connected to the safety equipment ground?

On the rear panel of the amp is there a signal ground lift switch by chance?


Lifting the ground makes the amp hum more
06-25-10: Williewonka
That would make sense if the signal ground of the amp is not connected to the chassis.
My use of the word Neutral does refer to the outer shell of the interconnect/phono socket

Using a multi-meter continuity tester and resistance settings I placed one probe on the outer shell of the amp and the other probe to the earth pin on the amp and there was no beeping from the continuity tester and the resistance setting showed a completely open circuit.

I asked NAIM about this and they confirmed this was how they designed the amp.

The ground on the amp is connected to the amp case/chassis for safety

They ground the neutral side of the signal in their systems at their source components

I did try "lifting the ground" on the amp and the hum got louder, but NAIM did not condone this practice and warned against it sighting safety.
One thing I've done in the past is bond all the metal cases together with a 14 or 16 gauge wire.That helped get rid of hum a lot of the time.
Hifitime -
One thing I've done in the past is bond all...

Be careful about doing this - components are designed very differently e.g. NAIM and Luxman - this could cause other problems that may be damaging - although I've read this solution many times on several forums- NAIM warns against this approach.

Cheers