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Post by Deleted on Apr 7, 2013 10:05:00 GMT
In a recent thread in C.A. there was a discussion about power supplies. I just posted the attached .Some members may find this of interest. Regards Alex
I previously mentioned the typical degradation in signal to noise ratio when using gear with an internal SMPS such as STBs, DVD players etc. connected to earthed equipment such as amplifiers. Even a DAC that is not in itself directly earthed may provide a direct path to I.E.C. earth at the amplifier. Just out of curiosity, a few minutes ago I checked a small +5V SMPS plug pack as supplied with a D Link router. I measured 81.9V AC between the -VE side of the supply and mains earth at the power board it was plugged into. This means that it is highly likely that smaller pieces of gear using SMPS plug packs (USB DACs etc.) are also likely to exhibit degraded performance when used in conjunction with power amplifiers using 3 pin mains plugs. Alex
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mrarroyo
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Post by mrarroyo on Apr 7, 2013 11:12:32 GMT
Alex, do you mind explaining what the 89.1V means for those of us not technically savvy. Thanks.
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Post by Deleted on Apr 7, 2013 11:47:05 GMT
Alex, do you mind explaining what the 89.1V means for those of us not technically savvy. Thanks. Hi Miguel It means that I read 89.1 volts of 50 Hertz mains voltage ( Alternating Current ) , but as it was coming via a small value capacitor in the plugpack, there was not enough current available to hurt you, just give a small tingle if you touched the plug while also making contact with an earthed object such as an amplifier's metal case. Regards Alex More at www.computeraudiophile.com/f8-general-forum/power-supplies-audio-gear-15649/index3.html#post218194
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Post by gommer on Apr 7, 2013 12:35:26 GMT
Euhm, Alex. You measuring AC or DC between a floating line and earth doesn't mean much, or does it? Any isolated SMPS is floating at it's output so you can expect to measure all sorts of things.
Have a look at this video, it's a bit tedious, but just as well informative on the subject and it shows just how much rubbish is picked up, no matter what the power supply is:
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Post by Deleted on Apr 7, 2013 12:45:29 GMT
Euhm, Alex. You measuring AC or DC between a floating line and earth doesn't mean much, or does it? Any isolated SMPS is floating at it's output so you can expect to measure all sorts of things. Have a look at this video, it's a bit tedious, but just as well informative on the subject and it shows just how much rubbish is picked up, no matter what the power supply is: Hi Marc There is an obligatory capacitor, or sometimes 2, in parallel between the primary and secondary sides of a typical SMPS to meet Regulatory EMI requirements. I have seen recently that in the case of a Dell laptop computer,Dell has documentation that explains that an allowable maximum leakage voltage is 50% of line voltage. I can send you a copy of an article with measurements and CRO screen grabs from various DVD players if you haven't seen it. Regards Alex
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Post by gommer on Apr 7, 2013 15:17:39 GMT
Alex, have you actually watched the video? This will show you that you have to ban ALL SMPS's in the neighborhood, not only the ones powering your equipment.
The problem is actually not the SMPS's themselves, but rather their implementation. They are in common use because of several reasons: price, efficiency and stand-by power. The problem is that they are also produced as cheap as possible and every cent counts. Thus EMI is only limited to just be within specs. Often not by reducing EMI, but by spreading power across the spectrum. Differential mode and common mode chokes are obviously avoided as the plague, as they are bulky, heavy and expensive. But principally, a SMPS could be designed to behave cleanly. A grounded one even more so.
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Post by Deleted on Apr 7, 2013 21:38:08 GMT
Alex, have you actually watched the video? This will show you that you have to ban ALL SMPS's in the neighborhood, not only the ones powering your equipment. The problem is actually not the SMPS's themselves, but rather their implementation. They are in common use because of several reasons: price, efficiency and stand-by power. The problem is that they are also produced as cheap as possible and every cent counts. Thus EMI is only limited to just be within specs. Often not by reducing EMI, but by spreading power across the spectrum. Differential mode and common mode chokes are obviously avoided as the plague, as they are bulky, heavy and expensive. But principally, a SMPS could be designed to behave cleanly. A grounded one even more so. Marc No, I haven't watched the video as it was too late at night, Did you receive the article I sent you ? I am aware of the problems that SMPS cause in general, including the huge start up currents that distort the mains waveforms, and in some cases where banks of equipment are turned on at the same time (groups of monitors for example) necessitating the installation of much larger circuit breakers (schools , etc.) On the user side, where you have several SMPS devices connected to the inputs of a preamplifier, even when in standby mode they can give you a very nasty bite (no longer just a tingle) when connecting/disconnecting the interconnects to a power amplifier, as the currents are additive. They don't appear to have taken this problem into account. This further degrades the performance of the audio chain unless you do as I have done in my preamp and also switch the "earth" side of all inputs. I agree that a grounded SMPS could be made to behave cleanly, but virtually all normal consumer products, as distinct from professional higher output current designs, which are often in metal cages, are not grounded. I am also aware that newly legislated requirements in some jurisdictions require them to have very small standby currents. Regards Alex P.S. I will look at your video after breakfast. BTW, I had to replace the crappy +5V SMPS plugpack for a D Link router yesterday, as it was often causing DLs to reduce to dial up speeds. Unplugging the plugpack, and then reconnecting it cured the problem for a while. There are several reports about crappy SMPS plugpacks supplied with D Link routers that may be found by Googling.
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Post by Deleted on Apr 7, 2013 23:33:42 GMT
Hi Marc We are talking about 2 different types of problems associated with SMPS supplies here. I have now watched the video right through, and it certainly gives further food for thought. Regarding the part about the interference from LED lighting, IIRC, Mike had his LED lighting replaced due to excessive radiated crap. I will link to your video in C.A. as it should be of interest to many people. Regards Alex
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pagan
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Post by pagan on Apr 8, 2013 3:16:35 GMT
Hi Marc We are talking about 2 different types of problems associated with SMPS supplies here. I have now watched the video right through, and it certainly gives further food for thought. Regarding the part about the interference from LED lighting, IIRC, Mike had his LED lighting replaced due to excessive radiated crap. I will link to your video in C.A. as it should be of interest to many people. Regards Alex Alex Was it LED lighting or Fluorescent? I've seen Flouro's giving noise but I didn't think Led's would have the same problem. Mainly because Led lighting is a lot lower voltage.
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pagan
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Post by pagan on Apr 8, 2013 3:32:51 GMT
Alex "I measured 81.9V AC between the -VE side of the supply and mains earth at the power board it was plugged into."
That's a lot of voltage on the neutral line in reference to earth.
What's the resistance between the neutral and earth without the SMPS plugged in?
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Post by Deleted on Apr 8, 2013 3:33:29 GMT
Hi Allan It was LED lighting. They are using crappy SMPS with mains powered LED lighting too. Some are worse than others. This has the potential to be far worse than normal fluoros.
Alex
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Post by Deleted on Apr 8, 2013 3:50:43 GMT
Alex "I measured 81.9V AC between the -VE side of the supply and mains earth at the power board it was plugged into." That's a lot of voltage on the neutral line in reference to earth. What's the resistance between the neutral and earth without the SMPS plugged in? Allan I presume you meant the DC 0 volts (outer) of the DC plug. I just read it as below 7Megohm then it climbed to unreadable. The same scenario between A,N, and E, as well as A and N. I then measured a 9V SMPS plugpack and a 12V SMPS plugpack to mains earth. Both read approximately 81.3V AC. Alex
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mrarroyo
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Post by mrarroyo on Apr 8, 2013 9:54:36 GMT
Alex, do you mind explaining what the 89.1V means for those of us not technically savvy. Thanks. Hi Miguel It means that I read 89.1 volts of 50 Hertz mains voltage ( Alternating Current ) , but as it was coming via a small value capacitor in the plugpack, there was not enough current available to hurt you, just give a small tingle if you touched the plug while also making contact with an earthed object such as an amplifier's metal case. Regards Alex More at www.computeraudiophile.com/f8-general-forum/power-supplies-audio-gear-15649/index3.html#post218194Ahhhh! the famous tingle, as we experienced with the now 4 year old green Novo/Solo. Grounding did help but even better with a regulated and linear PSU.
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Post by Deleted on Apr 8, 2013 10:02:31 GMT
Hi Miguel It's good to see that your memory is still as sharp as a tack. Yes, I remember that well, and hoped that you did too. Kind Regards Alex
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Post by gommer on Apr 8, 2013 10:29:49 GMT
Ah, amateur SMPS designers. I've recently finished sort of a 7kW SMPS with isolated secondary. No tingling there, although no FM reception either when it's working
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Post by Deleted on Apr 8, 2013 10:54:43 GMT
Ah, amateur SMPS designers. I've recently finished sort of a 7kW SMPS with isolated secondary. No tingling there, although no FM reception either when it's working I suppose that it needs it's own substation so that all the lights in the neighbourhood don't dim when it's switched on ?
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Post by gommer on Apr 8, 2013 11:03:17 GMT
Nah, the 16A 3x400 VAC will do. Teh lights did dim though while testing, but that had other causes We only need the private substation when testing a 200kW DC/DC.
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pagan
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Post by pagan on Apr 8, 2013 12:07:37 GMT
Hi Allan It was LED lighting. They are using crappy SMPS with mains powered LED lighting too. Some are worse than others. This has the potential to be far worse than normal fluoros. Alex Alex That's on LED lighting !!! So much for energy conservation. The standards for Australia IIRC was max 10ohm resistance between neutral and earth. They prefer lower. Voltage difference between neutral and earth at my place is approx 3V ac rms measured with my work Fluke. What the difference with yours between having the SMPS and not. If the voltage is caused by the SMPS leakage current then I would say it may have a problem. Allan
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Post by Deleted on Apr 8, 2013 12:23:55 GMT
Allan There is no problem (according to them ) . It's the way they are designed, They have high voltage, low value capacitors between the primary (230V) and secondary sides. These are used mainly because of legislated EMI requirements, and the values are chosen mainly to give the lowest EMI readings. Check your email Alex P.S. The 89V AC was read between mains Earth and the 0 volts side of the DC output plug. If you have a DVD-A player , most of which are SMPS powered, try reading between the outer of the L or R output socket and the case of your power amplifier without an interconnect plugged in.
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