Measurements for a dedicated line

The question of whether a homeowner should get a dedicated line is often like "should I get bangs." It’s a little complicated. Here are a couple of reasons to consider not:

I. My experience is that you won’t eliminate all the other noise coming from your home even if you do run a dedicated line. I still hear motors switching on and off despite being on completely different circuits.

II. A little resistance and a little inductance may actually be a good thing in keeping noise out of your line, so overkill on the wire gauge may not help this.

Why you definitely should get a dedicated line, with thicker wiring:


Less voltage sag.


Voltage sag means that under load the resistance in the line will cause the AC cabling int he wall itself to consume some of the AC voltage, giving your gear less volts to work with. This sag is proportional to current, so the more amps your gear is drawing the more sag.

This sag is something you can measure. There are two things you need to look: The hot to neutral voltage and the neutral to ground.

With nothing on the circuit your N-E (neutral to earth or ground) should be 2V or less. If it’s significantly higher than that stop and call an electrician. That’s true for any circuit in your home. High N-E values are indicators of a problem which may be in the circuit or in the service wiring from outside to the panel.

What happens when you turn your equipment on and play music is that the line will sag. The H-N (hot to neutral) voltage will drop, and the N-E will go up. Some sag as you turn on big amps is normal. So long as you are not tripping breakers you are fine. What you want to measure is the sag after your system has stabilized and while it’s playing music.

Keep an eye on the N-E value, as this will be a good indicator of the sag independent of the incoming line voltage. It may also point out where you may have issues. That is, if you measure an extra 2V of N-E, your sag is probably around 4V, so you went from 120V to 116V and you can be relatively comfortable it isn’t outside influences.

Of course, any good multimeter will work for this but I like plug in meters with built in N-E measurements. This one is cheap, and the N-E may not be hyper accurate, but it is the only device I’ve found on Amazon that will show you both the H-N and N-E voltages at the same time.

The nice thing about any plug-in type voltage meter is you can watch it over  a couple of days without hand holding probes in the socket.

If you find another which does both please post.




>>>With nothing on the circuit your N-E (neutral to earth or ground) should be 2V or less.<<<


I’ll be honest, I never check for this. What would be some of the causes for it?

-a less than optimum performing neutral

-leakage from the neutral to GND somewhere

@dpopov2272 Usually the cause is a bad connection upstream from you on the neutral circuit. Of course, having long runs/thin gauges contribute, but if yo find this number much higher it’s usually a bad upstream connection.

This can also happen if the neutral at the service panel is bad.

Let me rephrase, assuming your circuit has 0 amps, N-E voltage should be the same as at your panel, because 0 current = 0 volts dropped across your circuit.

So to be thorough, make sure your starting point is good.  if it isn't, you need an electrician right away. 

Next, once current is flowing through your circuit an excessively high N-E indicates excess resistance on the neutral.

@erik_squires Since I do pay a considerable amount of attention to power quality, bonding and grounding (bordering on OCD), and because of your provided link, I have now ordered this tester (mainly just for the N - E figure). I'm not sure I'm going to trust this device though after reading the 1 star reviews on Amazon. How do you think the tester obtains the N - E figure? Is the tester possibly converting ohms to volts for this test? Do you have to push a test button to see this figure, or is it always displayed?  

I agree completely with getting a dedicated line with thicker wiring. I would add that an Equitech 2Q or higher will be a wonderful complement. 


>>>once current is flowing through your circuit an excessively high N-E indicates excess resistance on the neutral.<<<


OK, this is starting to make a little more sense now. A device on the circuit being tested has to be consuming *some* current for the N - E figure to take place or appear. Got it.  

@dpop The N-E measurement is the same as the H-N, just volts. You can do the same with any multimeter. The ground wire normally has zero current, and remains at 0 V. The neutral though carries the same current as the hot. It’s that current that creates an elevated voltage. Consider:

V = A * R

So, on a lightly loaded circuit, with 1 Ohm, the neutral will be:

V = 5A x 1 Ohm = 5V.

The trick here is that the Hot will suffer the same voltage drop, 5V. So while the panel may be 120V, you have dropped 5V on the hot and 5 at the neutral so your wall socket will be 110 V just from voltage sag.


OK, this is starting to make a little more sense now. A device on the circuit being tested has to be consuming *some* current for the N - E figure to take place or appear. Got it.

The neutral wire has to have current to elevate the voltage above zero, yes, but you can still measure the voltage even if the voltage is zerol

@erik_squires noise is often mentioned but I would never install a dedicated line for noise control. to me the only real reason is to make is a size bigger to accomodate your amps rapid power needs. Mine is 10 awg. I admit I was lucky to have an abandoned 240V 10awg line for a dryer in the wall behind my system.

For noise I am a big believer in a rectifier/inverter such as the PSA PP.


@carlsbad2  - The one thing about the Class D power plants is that they do in fact output quite a bit of noise.  Personally I prefer to use an old-school voltage regulator. 

@erik_squires I assume you're referring to the new PP12 that weighs 1/3 what my PP10 does.  I'm still surprised that they output noise but I'm pretty sure my 90 lb behemoth isn't class D.  --Jerry

@carlsbad2 Honestly haven't kept up with them that closely.  I remember there was an original generation that was essentially using linear amplifiers, then they switched to Class D.

At the same time the founder of Jensen Transformers (really nice guy) founded another power conditioning company, Perfect Power?  Forgot the exact name, that used buck/boost transformers.  Very efficient compared to the PP, but still based on a linear amp.  Sadly that didn't really go anywhere. Sounded like an excellent compromise IMHO.

@erik_squires Thanks for the insight.  Yes, my PP10 is the original and the PP12 replaced it.  Even Paul once kindof ruminated that the PP10 might be the better option, especially for amps.  

Too bad about Jensen.  PS Audio is tough competition. but I'd like to see another option for the old school design.



If you are doing a dedicated line, there's a couple of interesting alternatives.  Getting a sub panel, and running 240V instead of 120V.

A sub panel means you run say 6 gauge wiring up to your listening room and then use short 12 gauge runs to each outlet.  Since you have 6 gauge wiring, your overall voltage sag is going to be negligible.

Another alternative is to run 240V and use a balanced power conditioner to step it down.  Again, you cut the current in half, therefore the sag is halved.

The neutral should have no more than 2 volts to ground. If you have more than that (as measured at the receptacle) the first thing to do is to go to all the outlets with a plug in receptacle tester and make sure they all read ’wired correctly’ and none read 'open ground', in which case call an electrician.

If the receptacles are okay, go to the panel and check to see if there is the same voltage between the neutral and ground bus or neutral and panel bond. If it is the same then that is pretty much the resistance to ground causing the neutral voltage. Check the panel bonds to both the panel and the ground rod.

If the voltage between G-N buss bars is a lot less than measured at the receptacles, then the most likely culprit is a loose connection somewhere in the circuit. First tighten all the lugs on the neutral and ground bars (a lot of times this will fix it). If that doesn’t do it then you have to trace the circuit for j-boxes and check or replace the wire nuts, then work your way to each receptacle and check the pigtails. If you have the backstab connectors, those too are a source of resistance.

Somewhere along the line a loose connection places a high impedance on the neutral creating a voltage divider, which shows as a few volts on the neutral.

I have a dedicated line and hear no such noise or interference from other circuits, motors etc  it also was not expensive or that difficult. I also did not go nuts, no need to. Simple 12 awg romex 50ft, 20 amp breaker, AQ nrg Edison receptacle. Sounds great, no noise that I can hear, and provides enough power to my class A sugden and all the rest. Did it myself to boot. 

@audioguy85  I did exactly the same thing, only my main floor run was 30 feet, and my basement system was 20 feet. I use a Cardas Audio 4181 receptacles. Same result Zero noise, larger soundstage, and more definition.

Combining, or "sharing" the Neutral Leg (white wire) can cause an imbalance of a voltage on the Neutral Leg. When a homeowner, or their "handy man" add an outlet, or a light fixture, or another modification to the home wiring, it is tempting to attach the modification to an existing circuit. It is not unusual to find a junction box with multiple neutral wires all connected together. The Neutral Leg has a relationship to Ground, but it is not to be treated like a ground. Stray voltage on the neutral can damage sensitive electronics, especially equipment, like computers, and electronics that operate on a reduced voltage (a power supply transformer is an indicator, which includes wall warts). Voltage on a neutral can indicate a problem out side of the distribution panel, yes. But more often it indicates wiring errors within the home. Stray voltage on the neutral is a problem, but usually it is a symptom of a problem with the basic wiring not being NEC (National Electrical Code, or NFPA 70) "Code" compliant. A separate distribution panel for your listening room does have some advantages, but it needs research and design to be of a true benefit. A qualified Master Electrician can, and should, inspect your wiring and panel for defects and deficiencies before proceeding. In older homes the wiring and protection (circuit breakers age, for example, and wiring and devices may be out of date and improper) may not be in compliance with current NEC "Code" requirements. It is worthwhile having a Licensed Master Electrician (there is stringent and frequent testing involved in moving from Apprentice, through Journeyman to Master. You don't get to self assign that title and award yourself a license) inspect the electrical service in your home and review with you a course of action, if needed. For less than the cost of a "power conditioner" you can have some certainty about the true condition about the quality of the electricity in your home. And then you can make an informed decision on how to proceed.

Dedicated power feed to house of stereo here with plug-in volt meter always displaying voltage. Always reading between 121 and 124 volts in dead of Summer or dead of winter. Not sure about the electrical specific points raised by Eric but a dedicated power feed has been a huge plus in my case. By example, my main house right next to it can fluctuate between 114 and 124 volts.

@baylinor You have really good house power! I have a quasi-dedicated circuit. It runs the HT and a USB house camera on it. I still have more fluctuations in voltage than that, even with nothing on. Typical voltages, with an unused circuit (except USB camera) runs 115-123V and my heat pumps and air handlers definitely move that needle as do the seasons.  BTW, I live in an area served by pad mounted transformers and underground feeds, so it should be relatively stable compared to pole mounted power.

I use a Furman voltage regulator as the "front-end" to my power conditioners to ensure the power is even tighter even when running the full system.

Just so readers understand, when a circuit has no load on it you are looking at the best case scenario.  Running a dedicated line won't get you better than that.

Where a dedicated line improves things is in the case of a circuit with load.  Less load + thicker cables should reduce voltage sag.

Point is, you can't do better than the panel voltage, and if it's going up and down, your dedicated circuit won't magically improve upon that.

Yes, I do have good power. Part lucky, part by design. The only loads I have in the house of stereo other than audio equipment are lighting and a Daikin Whisper Quiet AC/heat wall unit. Therefore a very constant feed no matter if it's all running or not. Simplicity is the key in this instance.

I received the test meter today that @erik_squires linked. Right off the bat I would say I’m impressed by its performance. One thing I look for in an AC voltmeter is how quickly it can measure and display voltage drops or variations. Even at ear splitting levels, one of my systems rarely consumes more than 1.5 amps on peaks, so I did not test it there, yet, as I doubt I’ll see much if any voltage fluctuation (10 AWG wire run about 15 feet from the load center). I did however put it on a variac, while quickly adjusting the power, simulating a huge momentary current draw on the line. The meter responded very quickly to this adjustment. All outlets that I’ve plugged it into so far are displaying 00 volts for the N-E figure. I am fortunate that I am fed directly from the step down transformer on the pole (I’m not at the end of the line) for my block. Even at that, during heavy summer cooling periods, I may see my total house voltage temporarily (for a few hours) drop about 2 volts. The meter doesn’t display tenths of volts for the L-N display, but using a reputable Fluke, the reading was only off by less than 1 volt. I would say it was easily worth the (roughly) $20 purchase price. My house voltage (on one leg I constantly monitor) typically remains at 120.7 volts 99% of the year.

@erik_squires you definitely got the quasi dedicated correct…. bummer…. Stromtank… and $ or € can fix that…..

Best to all in the quest for juice, AND clean juice….

Another plug in voltmeter that I really like is the Kill A Watt EZ meter. It measures a lot of things, but the voltmeter portion (which reads in tenths) is extremely accurate. 

Kill-A-Watt(Tm) Ez

@dpop Those are certainly popular, and I believe the original.  There are now dozens of watt / voltage meters out there, with a variety of smart features, including wifi connectivity.  What I've yet to find is one that measures N-E at the same time as the V.  Still, being able to chart your V over a week can really help you understand your power issues.

Using the KAIWEETS KM117B Socket Tester (the one @erik_squires linked), I took some measurements around my home:

My pizza oven consumes 11.5 amps during operation (measured using my
Amprobe ACD-10 TRMS-PLUS meter). With the oven off, AC volts available at the outlet is 121.3 - 121.5. With the oven on, volts available at the outlet dropped to 117.8. N-E volts 00 with the oven on or off.

My microwave oven consumes 14.6 amps during operation (measured using the amprobe meter). Volts available at the outlet with the microwave off was between 121.3 - 121.5. Volts available at the outlet with the microwave on was 117.9. N-E volts 00 with the microwave on or off.

My main audio system is a 3 power amp tri-amped system. The power amps alone consume about 1.5 amps total powered on with no program material. AC volts at the outlet is 121.5 with the amps off. With the amps on, volts at the outlet are 121.0. Peak amps measured at loudest passage was 1.9 amps (or, 0.40 amps above powered up status). The feed is 15' of 10 AWG directly from the circuit breaker box. N-E volts was 00 with the amps on or off.

My furnace consumes 3.79 amps with the unit in full operation (gas burner heating, and forced air fan blowing). Volts available at the outlet with the furnace off was 121.5. Volts available with the furnace full on was 120.5. N-E volts was 00 with the furnace on or off. 

What this does prove to me is how important a dedicated run *is* for power amps, or high current consuming integrated amps or receivers. 

@dpop Excellent investigations!! :)  While I applaud your work, should also point out how few amps you are drawing is contributing to the stability of the voltage. Your wiring could handle 30 Amps, and you are drawing 2 at peak usage. 

Audiophiles should evaluate the potential benefits vs. costs.  The longer the circuit from the main panel, the more the power draw is, the more worthwhile a dedicated, large gauge circuit becomes.

@erik_squires Good point Erik. I have a Panini maker which is rather light in weight, and easier to relocate vs. my pizza oven or microwave. It consumes 11.8 amps (the pizza oven consumes 11.5 amps). I plugged it into my 10 AWG main audio feed AC outlet. Volts available at the outlet at that moment was 121.8. Volts available with the Panini maker on was 119.0 (a voltage drop of -2.8 volts). N-E volts was 00.

I knew the 10 AWG feed was about 15 feet in length from the circuit breaker box to the measuring point. My other AC circuit feeds for my microwave and pizza oven I discovered are on the same 20 amp circuit as each other (good thing I never have a reason to run the pizza oven and microwave at the same time). The pizza oven and microwave are on a completely different circuit than my 10 AWG AC feed. My house was built in 1942, and the pizza oven wiring has never been updated, except with a new outlet at some point. The microwave outlet was installed at a later date, with copper wiring. The previous owners of the house had that installed. It was tied into the same circuit as the pizza oven outlet. Within the past 10 years I updated that microwave/pizza oven circuit breaker to the recent AFCI type. I’m guessing the wire run to the pizza oven outlet is around 20 feet, and the microwave outlet is 30 feet. Suffice to say there was more voltage drop at the pizza oven outlet (consuming roughly the same amount of amps as the panini maker), at -3.7 volts, than there was at my dedicated 10 AWG feed (-2.8 volts), consuming roughly the same amount of current.

Some of this was eye-opening, as I didn’t anticipate I would see that amount of voltage drop with high current demand at my 10 AWG feed, only 15 feet away from the circuit breaker box. One thing is for sure, I would not want to have any audio components on a microwave or pizza oven circuit when they would be in use.

My house was built in 1942, and the pizza oven wiring has never been updated, except with a new outlet at some point.


Ahhh! Yeah, you can’t do that today. The microwave gets it’s own circuit, which as of 2023 has to be CAFCI and GFCI protected.

Within the past 10 years I updated that microwave/pizza oven circuit breaker to the recent AFCI type.

Nice! Please make sure that all your kitchen counter top circuits are GFCI protected as well. Not sure if an outlet or updated breaker will be the most convenient for you in this case. Leave the fridge alone though, those trip GFCIs all the time. GFCI for kitchen counter top outlets has been code for decades but the latest 2023 NEC code expands GFCI to the dishwasher, microwave, and washer/dryer combos. I’m not sure you need to go that crazy, but I do think it’s worth the GFCI outlets on the counter tops for sure, and any outlets under a kitchen counter as well.

If you buy more GFCI outlets, any major brand but Leviton seem to have high trust factors with online electricians.


I have a dual gang countertop outlet that has a GFCI outlet in it. It is then connected to, and protects the outlet right next to it. The microwave is across the room, and isn’t within 6 feet of the kitchen sink. When I first moved in in 2001, I inspected and replaced all of the outlets in the house. When I changed out the pizza oven outlet, the insulation on the wires was cracking, and I told myself I hope I don’t have to replace this outlet for a long time after that - so I won’t be switching that outlet to a GFCI. Since we’re discussing this, I’ll probably change out the current AFCI circuit breaker for the microwave/pizza oven circuit with the combo CAFCI/GFCI type (I have a Siemens load center). Having been an apartment maintenance guy for over 10 years, we too never installed GFCI’s for refrigerators. 

@dpop Sounds good!!

GFCI outlets are cheaper ($20), but if it's not in a convenient location to reset when it trips then a new combination breaker is the way to go.

I also have Siemens.  My panel used 100% Siemens breakers, that were 15 years old when I moved in.  My neighbor had a weird assortment of breaker brands in hers.  I've replaced 100% of the single pole breakers and added a whole-house surge suppressor.  It makes me feel better, but I still lost a laptop in a storm that had no other surge protector on it.

I too have whole house surge suppression (never lost anything from storm damage the entire time I lived at this location - going on 23 years now), but since I have so much money wrapped up in audio, video and AC isolation and filtering gear, I sometimes contemplate spending the money on a higher quality surge protector. 

Sine Control Technology

@dpop The specs seem nice. One of the major issues with WHSP units is the high clamping voltage. The other is activation time. Another is the ability for a surge current to be induced by the AC wiring in the house.

For all these reasons, I still protect anything sensitive and/or expensive with a Furman or Tripp Lite at the outlets.

Still, I have sunk a lot of money into the advanced breakers, home automation, GFCI outlets and fire alarms in this house, so the WHSP unit in my panel is very worthwhile.

My dedicated line made a big difference in system sound quality, but still it sounds best after midnight and into the witching hours.

It's not component noise based on what I am not hearing through my horns. If it's noise or voltage on the lines I have no way of knowing that.

@bolong It would be nice if you got a plug - in V meter and could look at it during the day and night to see if you have better voltage at night.  I'd be really curious.

AC voltage, harmonic distortion and line frequency are all measurable. If there is a difference between night and day listening, and it's related to power delivery, we should be able to measure it. Personally I think some of this is psychological. Evening and night time listening hours are typically environmentally quieter, and your brain possibly adjusts to this. I've personally never measured any difference in power quality in my home environment between daytime listening and night time listening. One of my main listening rooms is down in my basement. The environment is intentionally blacked out all of the time (of course except when I light it), so that if this is a psychological thing, I can have a "night" environment whenever I want it. 

When I was a Radio Broadcast Engineer, I had a rack full of equipment in a transmitter room. This rack contained the audio processor for the FM transmitter. It created the audio signature of the FM station. The rack of equipment had a 20 plug power strip, and it was almost full. I plugged in my Fluke 43B Power analyzer, and discovered the Harmonic Distortion for this power strip was 0.0%. I kid you not. I was never able to find another AC plug that ever gave me that low of a Harmonic Distortion reading. The 3 phase power transformer for the building was on a pole right outside the door to this transmitter room.  

AC voltage, harmonic distortion and line frequency are all measurable


Indeed, but most of us can only measure AC voltage.  Harmonic distortion is definitely not something you get with your average multimeter, and the one thing I have the most faith in is the AC frequency.  So in the absence of anything else, it would be nice to correlate AC voltage with listening experience.

When I built my house, I had two dedicated lines wired with 10/2 gauge with ground, both going to hospital grade receptacles. Each one is connected to the same buss side at the breaker box. I’ve never heard any noise except a fluorescent light starter in my room where I store cables etc. I replaced it with a solid state starter which corrected the problem. All other low amperage equipment is connected to another line that are daisy chained. The two dedicated lines power two Krell FV-600 monoblocks. 

So when I came home yesterday evening my Kaiweets Outlet Tester I ordered from Amazon was waiting(love their next-day delivery) for me and couldn’t wait to try it. I’ll be dropping it off at Whole Foods today as it measured an astonishing 17 volts low. Measured with my Fluke 87 and Sperry both measured accurately within a fraction of a volt of each other. Too bad as it is a cool little device, now if only Fluke, Klein, etc., manufacture one of these.  I did see a very nice Klein voltage tester that while doesn't the voltage drop, it's an easy to read  tool for checking correct wiring on a large screen that has a memory when unplugged from the circuit.  With a Non-Contact Voltage Tester about twice the price.  Checkout the videos 



Unfortunately, it's a random draw with this one. Mine was within 1-2 volts. Others have reported as the poster in the thread did, that some can be much more off than that. Good news is [filtered] allows free returns. They do make other meters which get better ratings on reliability, but I dont' know of any that include the Neutral to Earth measurement standard.

So, A'gon apparently got upset with me that I said A M A Z O N in an e-mail.  Sheesh! :D

Post removed 

Are you sure you have an Equipment Grounding Conductor at the outlet?

100% most definitely; on both outlets being discussed. I can take my multimeter and read 121.6 volts across the hot and neutral (no load), and the exact same voltage is measured across hot and the EGC.

Maybe I’m not understanding you correctly, but I’m failing to comprehend why you think there should be some voltage on the EGC for these outlets (under load)? I was always under the impression that the EGC was to keep your equipment as close as possible to ground potential, and provide a safe path for ground-fault current to flow. My thinking is that if there was any voltage on the EGC, and I had in place a GFCI outlet; it would trip.

The voltage drop / 2 method only works if the voltage drop is equal.  It is possible the voltage drop is higher on the hot due to resistance. 

Best to measure with a multimeter for the most accurate results.