Evaluating Equipment-induced EMI noise in one’s audio system

So let’s begin!

My journey into this arena begins with my confounded findings of certain power line noise introduced into my audio system. In one instance, I did not understand how much EMI noise entered my audio system and the source of that noise. I had used a lot of AC power line conditioners and elaborate power line filters from a variety of reputable companies over the years. And a times, following the eventual equipment upgrade path many audiophiles find themselves suffering through, the power line noise would fluctuate to higher or lower noise levels with each reiteration of my audio system.

At a point in my last recent reiteration, I decided that I had enough of my ignorance. And so I developed a simple and effective test to evaluate specific components for their inherent noise level. First, the tools needed. I obtained an EMI noise measurement device. Many companies make decent ones. I went with a TriField model EM100.
 

Second, the method. I evaluated the audio component of interest on a conventional duplex wall outlet. I first measure the baseline power line noise on each outlet using the EMI measuring tool. That is essential because any deviation. from those baseline levels provide insight into the added (or reduced) EMI noise on the parallel line circuit when the audio equipment is connected to the second wall outlet of the duplex outlet. Based on the levels of elevated EMI noise my EMI tool measures above baseline measurement with the audio equipment item is connected and turned on can serve as a guide for one to assess whether one should accept or reject that equipment item into one’s audio system. Secondary measurements can be done with the equipment in the audio system in a similar manner using the EMI measurement tool, tho different test configurations might be required.

I’ve tested this method with four different audio equipment items to validate the approach to my satisfaction. I’ll share my data with two or three of these items below. 

Conditions with conventional duplex wall outlet; EMI Noise Level measurements from TriField EM100. 

Test audio component: power conditioner brand X with multiple power outlets on back. Majority of the “source” outlets are for providing power to source gear components; a secondary set of “power” outlets are for providing power to equipment like amplifiers. 

Two different power cables were used to provide power to the power conditioner brand X. This was done to rule out any possible EMI noise artifacts introduced by a given power cable that provided power to the power conditioner brand X. 

TriField EM100 connected to wall outlet 1 of 2 with nothing connected to wall outlet 2 of 2. 

EMI Noise Level: 72.4 mVp-p AC

TriField EM100 connected to wall outlet 2 of 2 with inothing connected to wall outlet 1 of 2. 

EMI Noise Level: 70.0 mVp-p AC

TriField EM100 connected to wall outlet 2 of 2 with power conditioner brand X off and connected to wall outlet 1 of 2 via BBQ power cable. 

EMI Noise Level: 61.7 mVp-p AC

TriField EM100 connected to wall outlet 2 of 2 with power conditioner brand X on and connected to wall outlet 1 of 2 via an Acoustic BBQ power cable. 

EMI Noise Level: 172.5 mVp-p AC

TriField EM100 connected to power conditioner brand X output source outlet with power conditioner brand X on and connected to wall outlet 1 of 2 via an Acoustic BBQ power cable. 

EMI Noise Level: 389.9 mVp-p AC

TriField EM100 connected to power conditioner brand X output power outlet with power conditioner brand X on and connected to wall outlet 1 of 2 via an Acoustic BBQ power cable. 

EMI Noise Level: 388.0 mVp-p AC

TriField EM100 connected to power conditioner brand X output source outlet with power conditioner brand X on and connected to wall outlet 1 of 2 via generic power cable. 

EMI Noise Level: 401.9 mVp-p AC

TriField EM100 connected to power conditioner brand X output power outlet with power conditioner brand X on and connected to wall outlet 1 of 2 via generic power cable. 

EMI Noise Level: 395.9 mVp-p AC

My conclusion: It’s clear from the measurements that the power conditioner brand X is an EMI noise generator that shouldn’t be used in a high-end audio system. 

Conditions with conventional duplex wall outlet; EMI Noise Level measurements from TriField EM100. 

Test audio component: an ultra-low impedance power conditioner brand Y without any  power outlets on back of the unit. The unit includes an attached dedicated proprietary power cable from the same manufacturer. The unit doesn’t include any active circuitry whatsoever. Accordingly, one might not expect this unit to generate any EMI noise into the line as a result of being connected to a wall outlet. The unit includes a toggle switch on the front panel to enable the user to select from two different “flavors” of ultra low impedance provided from the unit. 

TriField EM100 connected to wall outlet 1 of 2 with nothing connected to wall outlet 2 of 2. 

EMI Noise Level: 37.1 mVp-p AC

TriField EM100 connected to wall outlet 2 of 2 with inothing connected to wall outlet 1 of 2. 

EMI Noise Level: 37.5 mVp-p AC

TriField EM100 connected to wall outlet 2 of 2 with ultra-low impedance power conditioner brand Y connected to wall outlet 1 of 2 via the unit’s dedicated power cable and front panel selector “A” setting selected. 

EMI Noise Level: 40.1 mVp-p AC

TriField EM100 connected to wall outlet 2 of 2 with ultra-low impedance power conditioner brand Y connected to wall outlet 1 of 2 via the unit’s dedicated power cable and front panel selector “B” setting selected. 

EMI Noise Level: 43.3 mVp-p AC

My conclusion: It’s clear from the measurements that the ultra-low impedance power conditioner brand Y isn’t an EMI noise generator. The de minimus  increase in EMI noise is likely due to the dedicated power cable acting like an antenna. Based on these measurements. I see no reason for excluding the ultra-low impedance power conditioner brand Y from use in a high-end audio system. 

@steakster Regsrding the presence of a transformer inside the power conditioner brand X, I have no doubt that one is present. I don’t know its physical size and electronic properties. That said, I suggest it might be difficult to justify including a large transformer-based power conditioner into one’s audio system to reduce EMI noise if the same power conditioner is also introducing an additional layer of EMI noise into the system. Savvy audio designers should and do offer products that mitigate or altogether eliminate EMI noise from their designs. Those are the ones I’m trying to include in my system to the exclusion of others that are contributing more EMI noise than they remove.

Don't you agree?

Conditions with conventional duplex wall outlet; EMI Noise Level measurements from TriField EM100. 

Test audio component: a Class D monoblock amplifier brand Z with detachable, independent 300W GaN power supply. 

TriField EM100 connected to wall outlet 1 of 2 with nothing connected to wall outlet 2 of 2. 

EMI Noise Level: 22.6 mVp-p AC

TriField EM100 connected to wall outlet 2 of 2 with inothing connected to wall outlet 1 of 2. 

EMI Noise Level: 22.2 mVp-p AC

TriField EM100 connected to wall outlet 2 of 2 with Acoustic BBQ power cable connected to wall outlet 1 of 2. 

EMI Noise Level: 23.7 mVp-p AC

TriField EM100 connected to wall outlet 2 of 2 with only 300W GaN power supply connected to wall outlet 1 of 2 via the Acoustic BBQ power cable. 

EMI Noise Level: 25.3-25.8 mVp-p AC

TriField EM100 connected to wall outlet 2 of 2 with Class D monoblock amplifier brand Z connected to 300W GaN power supply connected to wall outlet 1 of 2 via the Acoustic BBQ power cable. 

EMI Noise Level: 54.8-61.9 mVp-p AC

TriField EM100 connected to wall outlet 2 of 2 with Class D monoblock amplifier brand Z connected to 300W GaN power supply connected to wall outlet 1 of 2 via the Acoustic BBQ power cable. (XLR input closed by XLR-RCA adaptor with RCA EMI/RFI blocker cap.)

EMI Noise Level: 67.0-81.2 mVp-p AC

My conclusion: While the 300W GaN power supply didn’t significantly increase EMI noise in the power line, the full Class D monoblock amplifier brand Z with the 300W power supply increased EMI noise by over 2-fold. I’m not certain whether such an increase in EMI noise will necessarily be audible, but it is present. 

@steakster I agree with everything you said in your recent post. I also don’t listen to my system with a TriField EMI measuring device. But I’m finding it as a useful tool to quickly decide whether a given component contributes significant EMI noise to the power line of the audio system. What remains to be assessed is the correlation of EMI noise to audible discernment of sound quality degradation as a result. 

Put a piece of shungite near the wall plug and measure it ...Cover the power supply with a plate of shungite...Neasure before and after ... Have fun...

Just a test... 😊

Merry Christmas to you and your family... 🎄

So did you find you enjoy the music more?

And then there’s the path from power to signal path, and sources power supply vs environmental RFI, vs AC power supply. And individual parts EMI generation. Rather complex issues and measurement problems to be identified prioritised and solved.

For me, a good cask strength bourbon helps. Makes the voices quieter also.

Will you reveal power conditioner brand Y?

Brand X can remain anonymous,  thus touting a brand yoy like and not giving any specific brand a thumbs down.

Watch M. Fremmer's You Tube journey to clean power. There are people and firms that specialize. If you have problems at the outlet, then all you can hope for is to alleviate or mitigate the actual issue, like plugging in the "right" "fix" between the outlet and your equipment. Maybe you will find a component that will satisfy, and then you won't have to address the real issues in your power distribution. Good luck. Bring in a Master Electrician and an Engineer for consultant and remedial steps, someone who specializes in "clean" power, hospitals, computers and Hi-Fi share this need. If you can swing it, a complete separate service from grid to meter to panel to ground (you are at the mercy of the grid...). Or a one to one isolation Xfrmer into an isolated distribution panel. A Motor/Generator might also be an answer, but not perfect, a DC system to AC, like solar and batteries might be the most elegant solution. Be sure of your equipment's electrical grounds. Balance the neutral leg (make sure each circuit has its own neutral (never "borrow" a neutral which leads to stray voltage, a difference of potential, on the neutral wire and always utilize a dedicated ground wire back to the single common ground in the panel). Have the Earth ground system tested (no clamping to a water pipe- that's a chance for difference of potential too; and there's a lot more non conductive plastic water pipe out there, a single earth ground in your distribution system is very important). It's likely most home distribution shows a voltage on the neutral, get that fixed. Eliminate any aluminum conductors in the system if you can (some older homes use Al wire, which has specific termination requirements, and for $$$ considerations from grid to meter is often Aluminum...). Isolate motors (vacuum cleaners appliances, hair dryers, etc.) to outside your protected distribution system. If a motor is necessary, vacuum/air pump, cooling fan, motion control...etc, DC ONLY, dedicated, and brushless. If your problem is RF, like a ham radio nearby or commercial transmitter, or big AC motors close to you, (water tower or other lift pumps, treatment plants for example), a Faraday Cage might be helpful with RF interference, Make sure each piece of your system is properly grounded. Some equipment will ground through the shield on an RCA, or the center wire in a balanced plug (two grounds to a unit is not ideal, go with the "best" grounding technique, or preferably the manufacturer's requirements). Learn the difference between capacitance noise and 60 cycle hum. Ideally one load per properly sized circuit breaker.  Quality solid wire is better than stranded, and don't over size the conductors, make sure they are sized correctly for their load (physics has had a recent revolution in electron motion theory, a big change from what I was taught). Surge and lightning protection at the input side of the panel (if you have eliminated motor noise and in rush, other wise circuit by circuit). Consider the effects of fluorescent, neon, and LED lighting, if possible do not share with your "clean" outlets (incandescent is a resistive load and should not usually cause problems). Use top quality components (brand name is a good place to start, then hospital grade and up..., outlets, junction boxes, wire, conduit, etc. These are things we have used to isolate delicate and sensitive computers, test equipment and sensors in a commercial manufacturing building situated in a heavily industrialized area, and also steps I have taken at home. The supply of clean, uniform power can turn into a money disposal unit. I suggest a professional work with you to IDENTIFY the issue(s) and then address them in a systematic way with quantifiable results.  But that's only my suggestion.

I treated my entire home using Rochelle Salt with  stunning  results  and little cost.

Those of you interested can do a Google search. 

Dear OP,  Do you think the irritating noise from the left speaker in below video has anything to do with EMI noise? Alex/WTA

There may be noise but the equipment rectifiers will filter out most of the noise, so the EMI noise may not be the main culprit because it will be filtered out.

Another thing to consider about the power conditioner or power regenerator is they lowered the impedance which improve the dynamic of the down stream equipment. It is something you could measure.

A lot of power filters which may filter out the noise but it increases the impedance which takes away the dynamic.