Popular Post Elberoth Posted May 7, 2017 Popular Post Share Posted May 7, 2017 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): [/img] 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: [/img] 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. sphinxsix, jventer, AudGuy and 3 others 6 Adam PC: custom Roon server with Pink Faun Ultra OCXO USB card Digital: Lampizator Horizon DAC Amp: Dan D'Agostino Momentum Stereo Speakers: Magcio M3 Link to comment
Elberoth Posted May 16, 2017 Author Share Posted May 16, 2017 Alex, I value your feedback very much and highly encoureage everyone to join the discussion. I know that a single digit meter is not a perfect solution. However, with all its limitations you can see a certain patterns here - namely, cheap SMPS in general generate much more noise than more expensive ones, designed with EMI radiation in mind (iFi iPower for example or genuine Apple iPhone charger vs chineese knock off). BTW - Cealin Gabriel (the CEO of Shunyata) have posted this info on another forum: 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. You may have noticed that he places much greater importance on the freq in the 100+kHz bands as more important to the performance of audio equipment. In other words - he doesn't seem to think 10kHz meter limitation is a problem. Superdad 1 Adam PC: custom Roon server with Pink Faun Ultra OCXO USB card Digital: Lampizator Horizon DAC Amp: Dan D'Agostino Momentum Stereo Speakers: Magcio M3 Link to comment
Elberoth Posted May 17, 2017 Author Share Posted May 17, 2017 19 hours ago, Jud said: Hi Adam. I would be very interested to know if any reason is given as to why these MHz frequencies should be important. A link is fine because I don't want to get off topic. The original thread: http://www.audioshark.org/power-conditioners-regulators-24/measuring-ac-power-line-noise-11713.html Adam PC: custom Roon server with Pink Faun Ultra OCXO USB card Digital: Lampizator Horizon DAC Amp: Dan D'Agostino Momentum Stereo Speakers: Magcio M3 Link to comment
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