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.




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