rodders3 Posted July 16, 2019 Share Posted July 16, 2019 For those of you that can measure such a thing, I'm interested to know what % of THD are you reading. I recently acquired an Isotek Sigmas 3 that provides the reading. At best, I'm getting low 3's and tonight when i got home and felt the need to blast Kylie's recently released greatest hits (don't judge!), i got a record of low 4's. I have no idea what is deemed reasonable. Link to comment Share on other sites More sharing options...
MooneeBeach Posted July 16, 2019 Share Posted July 16, 2019 9 minutes ago, rodders3 said: and tonight when i got home and felt the need to blast Kylie's recently released greatest hits Respect! 1 Link to comment Share on other sites More sharing options...
Ihearmusic Posted July 16, 2019 Share Posted July 16, 2019 I am trying hard to understand on how this thing could possibly give you a reading of THD!? 1 Link to comment Share on other sites More sharing options...
Ihearmusic Posted July 16, 2019 Share Posted July 16, 2019 Ah, I got it! Mains THD. It would be interesting to know what percentage change is needed to hear a difference. Link to comment Share on other sites More sharing options...
jt301 Posted July 16, 2019 Share Posted July 16, 2019 2 hours ago, rodders3 said: For those of you that can measure such a thing, I'm interested to know what % of THD are you reading. I recently acquired an Isotek Sigmas 3 that provides the reading. At best, I'm getting low 3's and tonight when i got home and felt the need to blast Kylie's recently released greatest hits (don't judge!), i got a record of low 4's. I have no idea what is deemed reasonable. I have the same power filter. I generally see figures around 5%. I’ve seen as low as high 3s and as high as 7%. I’ve just checked now and it’s low 5s. My question has always been is this the distortion coming in from the mains or is it the distortion coming out of the filter into my system. I can’t hear differences between high and low readings so I assume it’s the former. 1 Link to comment Share on other sites More sharing options...
Decky Posted July 16, 2019 Share Posted July 16, 2019 RMS distortion from a perfect sine-wave voltage (current)- I assume?? Even if this can be measured correctly I do not see how would that, so called "distortion", have any meaningful effect on an audio system. The function of mains filters is to deal with EMI / RF noise on the mains lines - not to correct the "distortion" of the input sine-wave. Nonsense! 1 Link to comment Share on other sites More sharing options...
HypnoToad Posted July 17, 2019 Share Posted July 17, 2019 You need to buy one of those hideously expensive power cables, apparently they fix everything. 1 Link to comment Share on other sites More sharing options...
Syrot Posted July 17, 2019 Share Posted July 17, 2019 (edited) Most energy suppliers in Australia should really work on 240 volts (+/-6%). Queensland has recently changed it supply specs to 230 volts (+10/-6 %). Mind you this is allowable voltage fluctuation and in reality it can be a lot more than this in regional areas or areas near large industrial installations that may draw more power during peak periods. I would assume if we are talking THD on a power source in this thread it would be the noise or distortion to the incoming AC sine wave. What most electronics don't like is the harmonic ripple that sits on the AC sine wave. Again the only real way to clean this up is to use high quality power conditioner or a UPS particularity online versions which will convert the AC to DC and back to clean pure constant AC. Otherwise if you have a well built electronics with inbuilt filtering in its power supply it should not be an issue. Fancy power cables nor will surge protectors have any effect on this. Edited July 17, 2019 by Syrot Link to comment Share on other sites More sharing options...
Audiophile Neuroscience Posted July 17, 2019 Share Posted July 17, 2019 21 hours ago, Ihearmusic said: Ah, I got it! Mains THD. It would be interesting to know what percentage change is needed to hear a difference. Yes, mains power THD is my understanding too. Clean power, always a fun topic, only second to cables in promoting friendly helpful discussion It has been claimed that both odd and even order harmonics of the sine wave may cause mechanical humming in transformers. It has also been claimed that DC offset can do this also. I can say that changing power circuits supplying an amp and /or using a power conditioner can make an audible difference to humming. Other more subjective improvements remain controversial but I remain open minded. That said I don't like to use power conditioners on power amps. Cheers David 1 Link to comment Share on other sites More sharing options...
stereo coffee Posted July 17, 2019 Share Posted July 17, 2019 14 hours ago, Decky said: RMS distortion from a perfect sine-wave voltage (current)- I assume?? Even if this can be measured correctly I do not see how would that, so called "distortion", have any meaningful effect on an audio system. The function of mains filters is to deal with EMI / RF noise on the mains lines - not to correct the "distortion" of the input sine-wave. Nonsense! Yes agreed,as mains frequency stability which is extremely concise, is not subject to any harmonics occurring. higher in frequency. THD is indeed the wrong term to use with mains currents and voltages. As an aside the use of the term THD for audio frequencies is not telling you a lot, rather any harmonic distortion should be properly stated in terms of the actual frequency harmonic it occurs at, not as a lumped figure that gives little indication of the spectra the distortion may or may not reside in. Link to comment Share on other sites More sharing options...
davewantsmoore Posted July 17, 2019 Share Posted July 17, 2019 On 16/07/2019 at 7:01 PM, rodders3 said: I have no idea what is deemed reasonable. For the THD of the electricity (like you are measuring) there are no rules.... but it is unlikely to be important. THD from the speaker (ie. THD of the sound pressure you hear) is a different thing to what you're measuring here. 1 Link to comment Share on other sites More sharing options...
Audiophile Neuroscience Posted July 17, 2019 Share Posted July 17, 2019 3 minutes ago, stereo coffee said: as mains frequency stability which is extremely concise, is not subject to any harmonics occurring. higher in frequency. Can you provide evidence this is not occurring? 3 minutes ago, davewantsmoore said: For the THD of the electricity (like you are measuring) there are no rules.... but it is unlikely to be important. Is there a rule that says it is unlikely to be important ? Link to comment Share on other sites More sharing options...
Volunteer sir sanders zingmore Posted July 17, 2019 Volunteer Share Posted July 17, 2019 On 16/07/2019 at 7:01 PM, rodders3 said: I have no idea what is deemed reasonable. If you can't hear it, it's reasonable 1 Link to comment Share on other sites More sharing options...
Audiophile Neuroscience Posted July 17, 2019 Share Posted July 17, 2019 2 minutes ago, Sir Sanders Zingmore said: If you can't hear it, it's reasonable Touche Link to comment Share on other sites More sharing options...
stereo coffee Posted July 17, 2019 Share Posted July 17, 2019 (edited) 57 minutes ago, Audiophile Neuroscience said: Can you provide evidence this is not occurring? Is there a rule that says it is unlikely to be important ? To measure frequency stability where you are can be done quite safely by measuring NOT the mains directly but the secondary ie low voltage side of a 12v AC transformer. Caution NEVER measure mains voltage or frequency directly using a oscilloscope or measuring frequency a conventional multimeter , rather if doing this ALWAYS USE - a fuse protected lower voltage isolating transformer. You could either use a oscilloscope which will easily handle 12v AC, or indeed a multimeter that has frequency measurement to measure 12v AC frequency stability. I did this a few nights ago with a multimeter and the frequency measuring the output of a 12v AC transformer was maintaining precisely between 49.9 and 50 hz I observed this over a ten minute period. This should by all accounts also be a rigid 50 hz where you live. Mains frequency generation to repeat is NOT subject to harmonics occurring. This is because of the total inability of the generation equipment to create any harmonic. Frequency of mains rather can alter slightly from its nominal value but is constantly monitored and adjusted accordingly typically during peak demands. https://en.wikipedia.org/wiki/Utility_frequency Edited July 17, 2019 by stereo coffee Link to comment Share on other sites More sharing options...
Audiophile Neuroscience Posted July 17, 2019 Share Posted July 17, 2019 40 minutes ago, stereo coffee said: I did this a few nights ago with a multimeter and the frequency measuring the output of a 12v AC transformer was maintaining precisely between 49.9 and 50 hz I observed this over a ten minute period. With respect your monitoring for 10 minutes hardly generalizes to all power supplies all the time. 40 minutes ago, stereo coffee said: This should by all accounts also be a rigid 50 hz where you live. With respect "by all accounts" is hardly scientific evidence 40 minutes ago, stereo coffee said: Mains frequency generation to repeat is NOT subject to harmonics occurring. This is because of the total inability of the generation equipment to create any harmonic. Repeating a statement does not make it true 40 minutes ago, stereo coffee said: Frequency of mains rather can alter slightly from its nominal value but is constantly monitored and adjusted accordingly typically during peak demands. Monitoring and aiming for a result is not the same as achieving the result 40 minutes ago, stereo coffee said: https://en.wikipedia.org/wiki/Utility_frequency Wikipedia is probably not the best reference, that said yours did not talk about harmonics,This one did https://en.wikipedia.org/wiki/Harmonics_(electrical_power) "Harmonic frequencies in the power grid are a frequent cause of power quality problems. Harmonics in power systems result in increased heating in the equipment and conductors, misfiring in variable speed drives, and torque pulsations in motors." It also talks about THD Link to comment Share on other sites More sharing options...
stereo coffee Posted July 17, 2019 Share Posted July 17, 2019 (edited) 44 minutes ago, Audiophile Neuroscience said: With respect your monitoring for 10 minutes hardly generalizes to all power supplies all the time. With respect "by all accounts" is hardly scientific evidence Repeating a statement does not make it true Monitoring and aiming for a result is not the same as achieving the result Wikipedia is probably not the best reference, that said yours did not talk about harmonics,This one did https://en.wikipedia.org/wiki/Harmonics_(electrical_power) "Harmonic frequencies in the power grid are a frequent cause of power quality problems. Harmonics in power systems result in increased heating in the equipment and conductors, misfiring in variable speed drives, and torque pulsations in motors." It also talks about THD You are referring I think to external influences on a national grid, not the grid itself which cannot create harmonics of its own generated frequency.( Read that again if needed ) You should find the national grid is sufficiently stiff with that frequency and current capability to not be influenced in the slightest, by domestic consumers. Which is not to say someone welding or using a motor nearby cannot create momentary added noise in some poorer distribution wiring situations. A good example of this is in parts of rural Australia where the old two wire systems delivery remain. But you will or should find with your own investigations, that the cyclic frequency of power delivery is amazingly stable. Quote Edited July 17, 2019 by stereo coffee Link to comment Share on other sites More sharing options...
Audiophile Neuroscience Posted July 17, 2019 Share Posted July 17, 2019 8 hours ago, stereo coffee said: You are referring I think to external influences on a national grid, not the grid itself which cannot create harmonics of its own generated frequency.( Read that again if needed ) *In the context of THD and harmonics* which is what this thread is about, you cited a Wikipedia reference that did not mention either two. The reference I cited FWIW stated, contrary to your opinion, "Harmonic frequencies in the power grid are a frequent cause of power quality problems. " With respect, I do not care where or how the harmonics got there, it is irrelevant to the question at hand. 8 hours ago, stereo coffee said: You should find the national grid is sufficiently stiff with that frequency and current capability to not be influenced in the slightest, by domestic consumers. That is your opinion. Thus far there does not appear to be evidence to that effect (which is not to say it doesn't exist) Addressing the OP's question, for which thus far the available evidence points to being a valid question, the answer remains not known (so far). @rodders3 I could not find the Isotek manual online (quick search only) but surely, if you have it, it gives some indication of what is supposedly acceptable THD? My quick search only found this https://www.isoteksystems.com/downloads/reviews/Genesis_Reviews.pdf The reviewer appears to be quoting from claims made by Isotek (they are not my claims): “An industrial electricity generator will give you a THD (Total Harmonic Distortion) of around 2-3% which is not good. To get a THD down to a preferred 0.3% is very difficult. Others have claimed such figures but we have independent tests that prove it. In fact our THD is always less than 0.2%, in general terms, and in the critical fifth harmonic it’s down to 0.06% which is extremely low. Rebuilding the mains is not a new concept, but to do it with a low distortion figure is hard.” 1 Link to comment Share on other sites More sharing options...
Volunteer sir sanders zingmore Posted July 17, 2019 Volunteer Share Posted July 17, 2019 Why is the fifth harmonic “critical”? Link to comment Share on other sites More sharing options...
Sub Sonic Posted July 17, 2019 Share Posted July 17, 2019 Here’s a quick read with info re frequency stability on the mains grid: https://energylive.aemo.com.au/Energy-Explained/Managing-frequency-in-the-power-system SS Link to comment Share on other sites More sharing options...
Sub Sonic Posted July 17, 2019 Share Posted July 17, 2019 I recall in previous times that a certain style of mains powered clock was used widely in commercial and industrial, these were locked to the mains frequency and never needed adjusting, indicating the frequency stability of the network. Of course, blackouts were then a problem... Link to comment Share on other sites More sharing options...
rodders3 Posted July 17, 2019 Author Share Posted July 17, 2019 1 hour ago, Audiophile Neuroscience said: *In the context of THD and harmonics* which is what this thread is about, you cited a Wikipedia reference that did not mention either two. The reference I cited FWIW stated, contrary to your opinion, "Harmonic frequencies in the power grid are a frequent cause of power quality problems. " With respect, I do not care where or how the harmonics got there, it is irrelevant to the question at hand. That is your opinion. Thus far there does not appear to be evidence to that effect (which is not to say it doesn't exist) Addressing the OP's question, for which thus far the available evidence points to being a valid question, the answer remains not known (so far). @rodders3 I could not find the Isotek manual online (quick search only) but surely, if you have it, it gives some indication of what is supposedly acceptable THD? My quick search only found this https://www.isoteksystems.com/downloads/reviews/Genesis_Reviews.pdf The reviewer appears to be quoting from claims made by Isotek (they are not my claims): “An industrial electricity generator will give you a THD (Total Harmonic Distortion) of around 2-3% which is not good. To get a THD down to a preferred 0.3% is very difficult. Others have claimed such figures but we have independent tests that prove it. In fact our THD is always less than 0.2%, in general terms, and in the critical fifth harmonic it’s down to 0.06% which is extremely low. Rebuilding the mains is not a new concept, but to do it with a low distortion figure is hard.” Thanks @Audiophile Neuroscience. I do have it in a box upstairs. When I get home I will have a look and let you know. Cheers, Rod 1 Link to comment Share on other sites More sharing options...
andyr Posted July 17, 2019 Share Posted July 17, 2019 13 minutes ago, Sub Sonic said: Here’s a quick read with info re frequency stability on the mains grid: https://energylive.aemo.com.au/Energy-Explained/Managing-frequency-in-the-power-system SS Very interesting - this I certainly didn't know: If the system has more power than it needs at any instant, its frequency will increase. If there is not enough power to meet demand at any time, the system frequency falls. So our power stability is going to get worse ... the more "variable generation" sources come online and "scheduled generation" sources are shut down. Thank you very much, greenies! Andy Link to comment Share on other sites More sharing options...
Audiophile Neuroscience Posted July 17, 2019 Share Posted July 17, 2019 6 minutes ago, andyr said: Very interesting - this I certainly didn't know: If the system has more power than it needs at any instant, its frequency will increase. If there is not enough power to meet demand at any time, the system frequency falls. So our power stability is going to get worse ... the more "variable generation" sources come online and "scheduled generation" sources are shut down. Thank you very much, greenies! Andy Yes, I also wondered how they dealt with things like the now ubiquitous solar panel generation from the guy next door. Link to comment Share on other sites More sharing options...
stereo coffee Posted July 17, 2019 Share Posted July 17, 2019 54 minutes ago, Audiophile Neuroscience said: *In the context of THD and harmonics* which is what this thread is about, you cited a Wikipedia reference that did not mention either two. The reference I cited FWIW stated, contrary to your opinion, "Harmonic frequencies in the power grid are a frequent cause of power quality problems. " With respect, I do not care where or how the harmonics got there, it is irrelevant to the question at hand. That is your opinion. Thus far there does not appear to be evidence to that effect (which is not to say it doesn't exist) However in caring, if for a moment that is possible I am really hoping so, it would help you to sort through external influences to a electricity grid which has some merit to know is there, and can be addressed to a degree by filters. vs not having to unnecessarily worry about harmonics that are impossible for the national grid to produce itself. Beginning to know vs presently not caring will help you pin point how these external aberrations can be solved. If you want some visual evidence of stability of the electricity supplies adherence to 50hz where you live, simply purchase a multimeter from the usual retail outlets that can read frequency and measure the output of a isolated fused 12v AC transformer - as I outlined in a earlier post. The better approach though for audio equipment is to design and use a better rectifier than the ubiquitous arrangement of diodes and capacitors we ponderously accept. Hands up how many of us have bothered to connect one of these in a audio system https://www.analog.com/media/en/technical-documentation/data-sheets/4320fb.pdf I raise my hand. Secondly optocouplers can help enormously to solve the majority of audio related noise and grounding issues. I also raise my hand. 1 Link to comment Share on other sites More sharing options...
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