kukynas Posted October 5, 2020 Share Posted October 5, 2020 as @MLXXX said measuring anything other than DUT won't tell you much, same applies if you plan to measure something like DAC's output, it'll be masked by post regulation and circuit noise and even if you decide to measure it you would need high res spectrum analyser and scope to see any meaningful numbers, I think I've seen measurements of the fancy cables somewhere but can't recall where... Easiest way would be to measure output of the transformer after rectifier and filtration, no matter if amp or dac, all you need is DC programmable electronics load with CC and CR, scope with very low noise front end (no need 16-18 bits, 8-10 bit is fine but with noise <100uV) and probe to measure transient, potentially probe for EMI/RFI if you wanna see the full picture and than a lot of spare time btw. just for fun https://sound-au.com/articles/mains-quality.htm I did something similar long time ago and couldn't found any correlation between low cost and expensive power cord, but if time permits during fixing my new preamp I can capture some of the measurements to show you difference between cheap power cord and Pangea cable I got for free with my amp. 1 Link to comment Share on other sites More sharing options...
davewantsmoore Posted October 5, 2020 Share Posted October 5, 2020 3 minutes ago, kukynas said: Easiest way would be to measure output of the transformer after rectifier and filtration, no matter if amp or dac.... Indeed.... but it doesn't account for other potential ways that power cables could possibly affect an entire system. The only real way to be conclusive is to the look at the output signal (as that is what you listen to). Quote it'll be masked by post regulation and circuit noise Yes.... it will. Link to comment Share on other sites More sharing options...
Assisi Posted October 5, 2020 Share Posted October 5, 2020 7 hours ago, rmpfyf said: Keen on thoughts for what people would think is of interest Thanks for tagging me. The matter of the benefit of power cables is of interest to me. However my knowledge of the what and how to measure anything audio wise is at best virtually negligible. I will follow the posts in the thread so that I may learn something. It will be interesting. John Link to comment Share on other sites More sharing options...
kukynas Posted October 5, 2020 Share Posted October 5, 2020 13 minutes ago, davewantsmoore said: Indeed.... but it doesn't account for other potential ways that power cables could possibly affect an entire system. Any hints? as mentioned several times on this forum and elsewhere what’s in the cable won’t go away just because we pluged in last 2 meters of fancy wire...and if someone thinks shielding of last 2 meters help eliminate EMI/RFI I suggest to pause for a second and rethink why wifi and radio frequencies works even through the walls 1 Link to comment Share on other sites More sharing options...
bob_m_54 Posted October 5, 2020 Share Posted October 5, 2020 (edited) 48 minutes ago, davewantsmoore said: Even a dummy load with a complex impedance (tailored to look like a speaker impedance) doesn't really represent a speaker... a speakers impedance fluctates with cone position. Eg: 8" woofer impedance (cone rest, in, out) ... but then it becomes very very difficult to control. The repeatability of microphone measurements of sound in a room is low when talking about a very high resolution. It is best to begin with the electric signal. If it cannot be shown (for example) that there is error introduced in the electrical signal (eg. in the DAC or the amp, or wherever) .... then a new hypothesis can be made which is that there wont' be any error at the speaker.... (and then you can worry about testing that) Sure. You can capture the sound coming out of the speaker in a way which maximises it's resolution and repatability.... but it is much lower reslution than looking at electrical signals. Eh? I'm the one saying that you need to look at the signal.. But I think you are looking too deep Dave, I can't see anything that will show up using a dynamic load, that won't be shown by a static load, and possibly more clearly. Edit: I forgot to mention one minor detail.. It's the rate and depth of movement of the voice coil that affects the impedance, not the position. Edited October 5, 2020 by bob_m_54 Link to comment Share on other sites More sharing options...
Stereophilus Posted October 5, 2020 Share Posted October 5, 2020 If we are measuring amplifier output, I would recommended considering using the same type of power cable on all connected equipment. This will improve the sensitivity of the results, but reduce the specificity. For initial inquiry this suits our needs. Also, a question regarding testing equipment. Will it share the same ground potential as the hifi gear? Does it need to? (I hesitate to post this last question...) does the test equipment need to also use the same type of power cable? These are speculative questions, not intended to rile the engineers amongst us, but to genuinely seek to account for possible variables. Link to comment Share on other sites More sharing options...
Stereophilus Posted October 5, 2020 Share Posted October 5, 2020 16 minutes ago, kukynas said: Any hints? as mentioned several times on this forum and elsewhere what’s in the cable won’t go away just because we pluged in last 2 meters of fancy wire...and if someone thinks shielding of last 2 meters help eliminate EMI/RFI I suggest to pause for a second and rethink why wifi and radio frequencies works even through the walls this is why the last 2 metres matter Link to comment Share on other sites More sharing options...
kukynas Posted October 5, 2020 Share Posted October 5, 2020 1 minute ago, Stereophilus said: this is why the last 2 metres matter what do you think is happeng prior to these last 2 meters anywhere between your distributor’s mains transformer and your wall outlet? 1 Link to comment Share on other sites More sharing options...
Guest rmpfyf Posted October 5, 2020 Share Posted October 5, 2020 I still think that the DAC/pre is where it's at - downstream only amplifies what comes out and waveform characterisation at large voltages and low error gets tricky. I don't think, in a relative sense, there'd be any significant difference in the magnitude of any audible effect (all things being equal). 1 minute ago, davewantsmoore said: It doesn't matter what is under evaluation if you can't reliably show a difference in signals. I think you will have your work cut out for you there. Take around 20% off there mate if a little research noted some static differences in parts that gave rise to no observable differences in a dynamic system, there's still valid findings. Link to comment Share on other sites More sharing options...
bob_m_54 Posted October 5, 2020 Share Posted October 5, 2020 Come on guys, lets stick to the topic.. Link to comment Share on other sites More sharing options...
aussievintage Posted October 5, 2020 Share Posted October 5, 2020 always wanted to do this... 1 Link to comment Share on other sites More sharing options...
Stereophilus Posted October 5, 2020 Share Posted October 5, 2020 Just now, kukynas said: what do you think is happeng prior to these last 2 meters anywhere between your distributor’s mains transformer and your wall outlet? Lots, but it is much less important than the last 2 metres. Link to comment Share on other sites More sharing options...
Guest rmpfyf Posted October 5, 2020 Share Posted October 5, 2020 50 minutes ago, davewantsmoore said: No, it's essential. Of course, though I'm recalcitrant to be too heavy handed in my opinions on an internet forum when I'm seeking feedback 50 minutes ago, davewantsmoore said: What that is going to tell you is, how valid will a test be where you use power cord A.... and then some time later use power cord B.... If you're getting errors of "X magnitude" running the same cord, ever few minutes ..... then unless these errors can be controlled for, or unless they are much smaller than the differences you get when using two differnent power cables..... then you can't see beyond them. Well... first thing is a power analyzer. Might even run a separate dedicated line in EMC cable, as the audio gear isn't currently getting unique soup so to speak. It'd be nice to find something with waveform capture for my budget, though that's likely, um, exxy. Link to comment Share on other sites More sharing options...
Stereophilus Posted October 5, 2020 Share Posted October 5, 2020 3 minutes ago, rmpfyf said: I still think that the DAC/pre is where it's at - downstream only amplifies what comes out and waveform characterisation at large voltages and low error gets tricky. I don't think, in a relative sense, there'd be any significant difference in the magnitude of any audible effect (all things being equal). So this is kind of my point. If power cables are doing something that is measurable, it is possibly due to localised effects on nearby equipment, such as a DAC and/or pre. Link to comment Share on other sites More sharing options...
Guest rmpfyf Posted October 5, 2020 Share Posted October 5, 2020 29 minutes ago, Stereophilus said: So this is kind of my point. If power cables are doing something that is measurable, it is possibly due to localised effects on nearby equipment, such as a DAC and/or pre. I'd think the effect is proportionate to the power consumption or rate thereof. Nothing to suggest they won't do anything to one of an amp or DAC/pre, both, or none. Link to comment Share on other sites More sharing options...
frednork Posted October 5, 2020 Share Posted October 5, 2020 Something I am sure you guys are all over but just in case... They never tested just a power cable, it was always at least " Vertex AQ power cord, Vertex AQ platform, and Quantum QX2." and subsequently even more I think (other cables)..... You might need to borrow some bits 1 Link to comment Share on other sites More sharing options...
Guest rmpfyf Posted October 5, 2020 Share Posted October 5, 2020 9 hours ago, frednork said: Something I am sure you guys are all over but just in case... They never tested just a power cable, it was always at least " Vertex AQ power cord, Vertex AQ platform, and Quantum QX2." and subsequently even more I think (other cables)..... You might need to borrow some bits Unlikely mate, if I can pull the bits over the next few months it'll be just cables. I'd doubt I'd be equipped to test anyhing else. Link to comment Share on other sites More sharing options...
Ittaku Posted October 5, 2020 Share Posted October 5, 2020 10 hours ago, frednork said: Something I am sure you guys are all over but just in case... They never tested just a power cable, it was always at least " Vertex AQ power cord, Vertex AQ platform, and Quantum QX2." and subsequently even more I think (other cables)..... You might need to borrow some bits Doing so obfuscates what's being tested to make it look like power cables cause a difference. Their "science" was terrible and worthless.; hence it is just marketing. What is being proposed here is proper science. Link to comment Share on other sites More sharing options...
frednork Posted October 5, 2020 Share Posted October 5, 2020 1 hour ago, Ittaku said: Their "science" was terrible and worthless.; hence it is just marketing. If that is truly the case , why would anyone be interested in replicating it? Link to comment Share on other sites More sharing options...
ray4410 Posted October 6, 2020 Share Posted October 6, 2020 15 hours ago, kukynas said: Any hints? as mentioned several times on this forum and elsewhere what’s in the cable won’t go away just because we pluged in last 2 meters of fancy wire...and if someone thinks shielding of last 2 meters help eliminate EMI/RFI I suggest to pause for a second and rethink why wifi and radio frequencies works even through the walls a good quality fully shielded power cable will eliminate rfi+emi from contaminating your system, i have checked this with best and most accurate measuring device available,my own ears.,think of the tight woven power cord outer shield as a faraday cage,your house walls do not have such a thing,10mm of plaster each side. Link to comment Share on other sites More sharing options...
Guest rmpfyf Posted October 6, 2020 Share Posted October 6, 2020 6 minutes ago, ray4410 said: a good quality fully shielded power cable will eliminate rfi+emi from contaminating your system, i have checked this with best and most accurate measuring device available,my own ears.,think of the tight woven power cord outer shield as a faraday cage,your house walls do not have such a thing,10mm of plaster each side. I'm a fan of using bog standard EMC cable and some decent plugs. Would be interested to see how a 'recipe for common sense' stacks up in numbers. Link to comment Share on other sites More sharing options...
bob_m_54 Posted October 6, 2020 Share Posted October 6, 2020 4 hours ago, ray4410 said: a good quality fully shielded power cable will eliminate rfi+emi from contaminating your system, i have checked this with best and most accurate measuring device available,my own ears.,think of the tight woven power cord outer shield as a faraday cage,your house walls do not have such a thing,10mm of plaster each side. Which is why any RFI or EMI is already on the power cable, and the shielding won't remove it. 2 Link to comment Share on other sites More sharing options...
kukynas Posted October 6, 2020 Share Posted October 6, 2020 4 hours ago, ray4410 said: a good quality fully shielded power cable will eliminate rfi+emi from contaminating your system, i have checked this with best and most accurate measuring device available,my own ears.,think of the tight woven power cord outer shield as a faraday cage,your house walls do not have such a thing,10mm of plaster each side. as I said in my previous post and Bob below... it's there already and won't magically disappear just because we added 2 meters of additional shielded cable... 9 minutes ago, bob_m_54 said: Which is why any RFI or EMI is already on the power cable, and the shielding won't remove it. just to add few more points to consider: - mains voltage fluctuate during the day, even every minutes or seconds, so to be able to properly measure 2 different cables you need to set some error expectation, how big I don't know - ripple, harmonics, noise and who knows what else also fluctuate depends on how many other houses/companies are connected to the same grid - different appliances within your house contributes to overall result, LED lights, fridges, aircos, wifi etc... 1 Link to comment Share on other sites More sharing options...
bob_m_54 Posted October 6, 2020 Share Posted October 6, 2020 4 hours ago, ray4410 said: a good quality fully shielded power cable will eliminate rfi+emi from contaminating your system, i have checked this with best and most accurate measuring device available,my own ears.,think of the tight woven power cord outer shield as a faraday cage,your house walls do not have such a thing,10mm of plaster each side. Actually, I can expand on that, and have had personal, documented experience of why putting a Faraday Cage around the last 2M of power cable doesn't achieve anything in the way of removing RFI/EMI. Many years ago, in the RAAF, I was doing maintence checks on Emergency Radio Beacons. Obviously this had to be done in a screened room, yes a large Faraday Cage. If not, and you did the ERB output check, you'd be transmitting the siren tone on Military Guard Frequency 243MHz, and very soon you'd hear a chopper above your head. Well this day, I was in the room, checked the door was fully closed, and proceeded to check half a dozen ERBs. Half an hour later the Warrant Officer came bursting in ... What the @%$#%^ are you doing, I've got the tower on the phone and the SAR chopper is doing circles above us. Then he looked over and saw a transistor radio on the end of the bench (turned off), with a long piece of wire connected to the antenna, and disappearing through a tiny hole in the double copper meshed wall. A bloke the night before got bored and decided to listen to the radio, and when he couldn't a signal in the screened room (who'd a thunk) he decided to run a wire through the mesh wall, and it worked perfectly. It also worked perfectly to pick up the output RF from the beacon, emitting it from the other end of the wire (outside the cage). Your house wiring is like the antenna wire, into your Faraday Cage.. Oh yeah, as for the documentation of it.. All emergency transmissions are logged.. LOL 2 1 Link to comment Share on other sites More sharing options...
davewantsmoore Posted October 6, 2020 Share Posted October 6, 2020 20 hours ago, rmpfyf said: Of course, though I'm recalcitrant to be too heavy handed in my opinions If your goal is to be able to make certain statements about your results... then I consider it more fact than "opinion". Link to comment Share on other sites More sharing options...
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