Measuring AC Power Line Noise

CGabriel said:
Jim, you are right. It is only $130 which any dealer should be willing to invest in.

We have received three of them and will be testing to see how useful they are. One caveat, as with all measurement tools especially simple ones there may be a tendency to rely on a single parameter to make decisions. All of these type of devices will only give a rough (averaged) reading of noise on the power line. There is no way with these to know "which" frequencies are actually on your specific line. And of course the noise components between locations and cities will be different. So as with the Enteq, this will be primarily useful to hear/see "relative" differences on a specific line at a specific time.

That said, it looks like a useful tool to have at your disposal. For example, using the Enteq at my house I found that I had a very strong radio station being picked-up by my upstairs power lines. I also could hear the very distinctive sound of LED lighting noise pollution. Quite insidious actually.
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I came across another unit which seems to be very similar. It's called the "Stetzerizer Microsurge Meter"
No sound from it. But I've seen it pick up LED, Florescent, etc.
It's units are made up by it's designer. But they equate to 24volts/second.
With these units it's said to demonstrate both large spikes and high frequency.
No idea the efficacy of it. But Caelin could probably elaborate.
I'm too new here, so unable to post a direct link. But Google works well enough.

http://www.stetzerizer-us.com/Original-STETZERiZER-Graham-Stetzer-Filters_c_9.html
 
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Champ said:
I came across another unit which seems to be very similar. It's called the "Stetzerizer Microsurge Meter"
No sound from it. But I've seen it pick up LED, Florescent, etc.
It's units are made up by it's designer. But they equate to 24volts/second.
With these units it's said to demonstrate both large spikes and high frequency.
No idea the efficacy of it. But Caelin could probably elaborate.
I'm too new here, so unable to post a direct link. But Google works well enough.

http://www.stetzerizer-us.com/Original-STETZERiZER-Graham-Stetzer-Filters_c_9.html
Click to expand...

I have several of the Alpha and the Stetzerizer units. Personally, I prefer the old Entech unit. Entech was actually a very technically advanced group of engineers. Both the Alpha and Stetzerizer are similar in that they have a bandwidth that extends quite low for measuring RFI/EMI. They drop down to 15-30 kHz in there measurements. While this may seem to be an advantage it actually has a fatal flaw. Both aggregate noise from about 15 kHz to around 10 MHz and lump them all together in a single reading. Some frequency bands are more important to the performance of audio equipment specifically our research indicates the the most harmful frequencies are in the 100 kHz to around 1 MHz bands and then secondarily from 1 MHz to 10 MHz. Interestingly, I believe that the Entech engineers knew this and designed their device to be sensitive in the frequencies from 300 kHz to 700 kHz range. This makes the Entech particularly useful for finding noise sources in the specific ranges that are most noticeable in the context of music systems.

I have done direct side-by-side comparisons using all of the units listed. I would then plug a device into the power line that we 'know' produces particularly harmful noise effects as measured by our power and spectrum analyzers. In many cases, the Alpha and Stetzerizer would barely change their relative readings while the Entech would go off the charts. This is because the Entech is more narrowly focused and the other two are less so.

And then conversely I would connect filters that reduce power line noise in a known manner as verified by the power and spectrum analyzers and in many of these cases the Alpha and Stetzerizer would show only as small or marginal difference while the Entech would show a much larger and significant difference.

Look these are all very inexpensive devices and all of them can be useful. But they have severe limitations from a technical point of view. I found the most useful for the hobbyist to be the Entech. As I said earlier, we are developing a device that will be much more useful and will show noise in specific bands much like the old audio spectrum displays. This is being developed for our medical division where this device will be quite useful in identifying specific types of noise pollution in hospitals. I hope this is helpful.

BTW, I have three of the Alpha units and would be happy to sell two of them at less than what we paid for them. Just PM me.
 
BTW - I have spoken with the guys from Gigawatt on topic of the AC measurements, and inhouse they use this:

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Keysight PA2201A IntegraVision Power Analyzer

http://www.triotest.com.au/store/si...vision-power-analyzer-2-channels-1-phase.html

I need to somehow negociate borrowing it for a day or two as Adam (the Gigawatt owner) is a good friend of mine.
 

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Adam, well Gigawatt as you know are very professional and are doing some amazing things. Having the best testing equipment helps.
 
I think I can see one of their units in my future :)

I have never considered one, as 'straight to the wall is best' - as we all know ;) But after measuring the noise on my AC line, I'm not so sure anymore.
 
Every PSU kicks some noise back into the AC line, which may have an influence on the rest of your gear connected to the same AC line.

I still remember a review written by Martin Colloms of some gear using onboard SMPS, where he claimed that simply connecting said component (otherwise not connected to the system) to AC line, made his system sound considerably worse.

So how bad is the problem ? Having bought a wideband AlphaLab EMI Power Line Noise Meter I decided check that out on various PSUs I had on hand.

The setup

To get a reference/base noise level I have used my old and trusty Audio Power Industries Power Wedge Ultra 215 power conditioner, which I normally use to 'sink' all of my computer related PSUs - main server PSU, SSD battery SMPS charger, UpTone Audio JS-2 powering two LPS-1 PSUs and a computer monitor.

The noise level measured at the output was just 23mV. I have used one of outputs to connect a simple power strip (with no filtering):




The PSU under test was connected to the same power strip, next to the EMI meter:





I had 8 different PSUs on hand: 3 linear ones and 5 SMPS (switch mode) types:





1. Teddy Pardo linear PSU
2. UpTone JS-2 linear PSU
3. SOtM supplied SMPS (PowerTek)
4. Meanwell SMPS (supplied by UpTone with Regen and LPS-1)
5. Some generic linear PSU I found lying around
6. Ktec SMPS that I got with an external HDD
7. iFi iPower SMPS
8 Co Ming Data SMPS

Since I have observed the level of noise beeing kicked back to the AC line varies with PSU load, I have measeured those PSUs in the following conditions:

1. Idle - PSU connected to the power strip, but nothing connected to the PSU (no load)
2. Noise under light load - PSU powering Regen, which in turn was powering AQ DragonFly DAC
3. Noise under moderate load - PSU powering SOtM sMS-200
4. Noise under heavy load - PSU powering the LPS-1 Ultracapacitor PSU, which in turn was powering the SOtM sMS-200.

The results I got are as follows (green = best case; red = worst case):


Please note that the smallest, generic linear PSU (last column) was not tested with LPS-1, since its power rating was too small.

Some things I have noticed:

The SMPSu in general injected much more noise than linear ones. Even the cheapest generic wall wart linear PSU was better than the best SMPS.

In many cases, the noise figures dropped at idle a few mV below the reference level. It is my understanding that this is due to filtering built at the input of those PSUs, which interacts / lowers the noise on the AC line.

The PSU noise readings were jumping up and down when the LPS-1 PSU was connected (chence the results are in ranges). You can see this on a short video I uploaded on youtube.



It is my understanding that noise spikes were caused by the LPS-1 bulit in (capacitor) charger - when the charger was running, the noise was higher; when the charger was idling, the noise was lower. I'm not sure if higher noise readings are caused by higher current draw or the noise is comes from the LPS-1 charger itself. Whatever the reason - some PSUs were much more sensitive to that than the other.

For kicks, I have also measured several other PSUs and even light bulbs:



- iPhone, iPad and MacBook chargers are pretty harmless when at idle. I wouldn't want to have one connected to my powerstrip when charging though (all of you using MacBooks and other laptops connected to your system take note).
- CFL light bulbs (and LEDs) are huge noise generators (unlike regular light bulbs, which generate close to zero noise).
- chineese iPhone charger knock off from ebay, creates some absurd amounts of noise - many times more than the original Apple accessory (one more reason not to buy knock offs).
- TeraDak linear ATX PSU that powers my CAPS v4 Pipeline server generate generates only 48mV of noise - suprisingly litte.

Final notes:

If you have lots of those generic SMPS around your audio system (powering DACs, HUBs, routers, external HDDs etc), it probably makes sense to replace them with something designed with the AC noise pollution in mind, like the $49 iFi iPower SMPS for example. Linear still seems to work best though.

Having said that, please remember, that the best PSU is not necessarily the one which kicks the least amount of noise back into the AC line. The best PSU is the one that has low AC noise footprint and offers stellar DC output performance.
 
8 months later, wondering if Shunyata has made any progress toward developing a consumer grade noise analyser?
 
Jim Smith said:
My Sound room & office have their own transformer on a pole about 20' behind the building. Separately fed (and billed by the power company) from the house feed which comes in from a different pole & transformer.

Readings are generally 175-125 in my demo room, on dedicated circuits. House readings can be as high as 2000, depending on where I measure and what is running.

Wish I had a way to try a power conditioner & measure the results. Don't know if my readings are high or not. I thought of visiting my local dealer who is a friend and measure his readings with & without the P.C. in his store. But he has AQ, not Shunyata.

The sound here is very dynamic, yet very quiet & smooth, but I still have that perfectionist disease...:huh:
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Jim, I was wondering if you ended up trying the Denali Conditioner and if you found it helped your system?

I have tested the power in my room with the Alpha meter getting consistent readings around 250 mV and am curious
if a conditioner would be useful for my relatively low powered system: 30 watt/channel tube amp and high efficiency
horn speakers.

And finally, if you have any thoughts comparing Shunyata offerings to PS Audio's? Thanks
 
Any power line noise measurements need to be made with the circuit loaded. I use a 500 watt oil filled room heater near the meter test point.

But on the other hand, much of the power line noise will be generated by the hi-fi components themselves, so also test using the hi-fi system rather than the dummy load.
 
Yes Alpha Labs makes some nice meters that wound be useful in tracking down the noise makers around the home. But follow my above post or you may be chasing phantoms.

And a lot of the bad readings have no impact on sound quality. Good circuit designers know how to deal with AC power.
 
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Willco said:
Jim, I was wondering if you ended up trying the Denali Conditioner and if you found it helped your system?
Click to expand...

Nope, never got around to it.

Willco said:
And finally, if you have any thoughts comparing Shunyata offerings to PS Audio's? Thanks
Click to expand...

My last comparison was at least 5 years ago. I preferred - and purchased - the Shunyata then.

I don't use any power conditioning in the new room.
 
Just found an Entech Line Analyzer for a reasonable price but have not received. I thought about the Alpha Labs meter but I could not find any online manual and does not appear to be contact info readily available.

From online sources, cover of Entech unit says to adjust the noise meter to get 80-120 on display with Over-Range light OFF.

I assume this is done with unit unplugged?

Is Entech suggesting that 80-120 is an acceptable range? I am guessing less is more.
 
What are some suggestions on a real analizer that will test for high frequency noise, harmonics, DC etc. Anyone know a good all purpose tool?
 
Well designed hi-fi components should be able to deal with a goodly amount of power line junk. The real question is does any of this junk get to the audio line or speaker outputs. The easiest measurement is the output signal to noise ratio. With other equipment a FFT test and an O-scope looking for out of band problems.
 
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