davewantsmoore Posted October 6, 2020 Posted October 6, 2020 9 hours ago, rmpfyf said: I'd doubt I'd be equipped to test anyhing else. Why not? If you testing the output signals of a dac/pre/amp .... then you could have anything else you want in the system.
davewantsmoore Posted October 6, 2020 Posted October 6, 2020 8 hours ago, Ittaku said: 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. Their method seemed fine in general, for what it was. Presenting the results more cafeully, and as you say, testing one thing at a time, and presenting more cafeult controls.... might tell a different story... and will at least tell a clearer story.
davewantsmoore Posted October 6, 2020 Posted October 6, 2020 20 hours ago, Stereophilus said: 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. Once the test is setup and well controlled, then it should be easily possible to test anything you want.... any combinations, etc. etc.
pwstereo Posted October 6, 2020 Posted October 6, 2020 (edited) 22 minutes ago, bob_m_54 said: ... 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. Yes, I don't see how it can act as a filter for mains-borne interference. It could really only hope to stop that 2 metre cord picking up new interference in the distance from the outlet to the equipment. And the comparison of power cables documented here: seems to be testing for radiated interference. It demonstrates that shielding reduces the radiated field from a power cable. Edited October 6, 2020 by pwstereo Fixed link 1
bob_m_54 Posted October 6, 2020 Posted October 6, 2020 (edited) 13 minutes ago, pwstereo said: Yes, I don't see how it can act as a filter for mains-borne interference. It could really only hope to stop that 2 metre cord picking up new interference in the distance from the outlet to the equipment. And the comparison of power cables documented here: seems to be testing for radiated interference. It demonstrates that shielding reduces the radiated field from a power cable. Yep, that's what shielded power cables do. Handy if you're trying to avoid the power cable polluting near by signal cables. Edited October 6, 2020 by bob_m_54 1
davewantsmoore Posted October 6, 2020 Posted October 6, 2020 Quote Eh? I'm the one saying that you need to look at the signal.. Sure... I am just bring to attention that a dummy load (even one with a complex imedance) can be a complete softball to an amplifier.... and might hide what you're trying to find. That doesn't mean you can't start with a dummy load. 20 hours ago, bob_m_54 said: 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. At certain frequencies the A/C power draw of an amplifier is modulated agressively by the speaker load (it's impedance flutactes with every beat of the cone). The dummy load dos not do this. The way around this is to measure the amplifier output with the speaker in the circuit.... however this adds huge variation to the results.... and why you will find is that you are looking for things smaller than you can measure accurately, that way. 20 hours ago, bob_m_54 said: 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. Now, perhaps it's my turn to say "I don't understand why you are trying to correct me". The "rate" of movement.... being the frequency, of course, does affect the impedance (but that isn't what I was talking about). The "depth" of movement. .... I assume you mean "how far the cone moves"..... ie. the position of the cone. This is why it is called Le(x).... X being the position of cone. At differing frequencies, the reason for the position dependant impedance changes. At Fs/Fc, it's to do with the mms resonance..... At high frequencies its due to Le(x). The point being that at some frequencies the impedance changes quite substantially as the cone moves.
bob_m_54 Posted October 6, 2020 Posted October 6, 2020 (edited) 13 minutes ago, davewantsmoore said: Sure... I am just bring to attention that a dummy load (even one with a complex imedance) can be a complete softball to an amplifier.... and might hide what you're trying to find. That doesn't mean you can't start with a dummy load. At certain frequencies the A/C power draw of an amplifier is modulated agressively by the speaker load (it's impedance flutactes with every beat of the cone). The dummy load dos not do this. The way around this is to measure the amplifier output with the speaker in the circuit.... however this adds huge variation to the results.... and why you will find is that you are looking for things smaller than you can measure accurately, that way. Now, perhaps it's my turn to say "I don't understand why you are trying to correct me". The "rate" of movement.... being the frequency, of course, does affect the impedance (but that isn't what I was talking about). The "depth" of movement. .... I assume you mean "how far the cone moves"..... ie. the position of the cone. This is why it is called Le(x).... X being the position of cone. At differing frequencies, the reason for the position dependant impedance changes. At Fs/Fc, it's to do with the mms resonance..... At high frequencies its due to Le(x). The point being that at some frequencies the impedance changes quite substantially as the cone moves. ie. As the turns on the coil cut the magnetic lines of flux from the magnet, inducing a current to oppose the movement... No movement, no counter current. hahaha I stuffed up the wink Edited October 6, 2020 by bob_m_54
kukynas Posted October 6, 2020 Posted October 6, 2020 42 minutes ago, bob_m_54 said: 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 oh yes, add lab grade scope/analyzer with differential and current probes costing sometimes more than your analyzer, eliminate all possible variables with regulated active filter and you quickly realize the light at the end of the tunnel is further away than you originally thought, than add potential deviations and errors in your measurements to be perfectly ready for argumentative discussion about your wasted time... I'm saying hats off and good luck
Guest rmpfyf Posted October 6, 2020 Posted October 6, 2020 1 hour ago, davewantsmoore said: If your goal is to be able to make certain statements about your results... then I consider it more fact than "opinion". My immediate goal is to keep a thread going in a constructive manner
bob_m_54 Posted October 6, 2020 Posted October 6, 2020 7 minutes ago, kukynas said: oh yes, add lab grade scope/analyzer with differential and current probes costing sometimes more than your analyzer, eliminate all possible variables with regulated active filter and you quickly realize the light at the end of the tunnel is further away than you originally thought, than add potential deviations and errors in your measurements to be perfectly ready for argumentative discussion about your wasted time... I'm saying hats off and good luck Don't need to, it's way more simple than that, as I illustrated above
kukynas Posted October 6, 2020 Posted October 6, 2020 I don’t need to either but if anyone decide to do it it’s good to do it properly otherwise it’s potentially wasted time and money 1
MLXXX Posted October 6, 2020 Posted October 6, 2020 1 hour ago, bob_m_54 said: 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. ... A very interesting anecdote. If a power cord included small value capacitors between active and neutral (located at either end of the cable), that would tend to reduce the amplitude of mains borne Radio Frequency Interference. On the other hand, audiophile equipment might well already include chokes and/or capacitors to attenuate incoming mains borne RFI. 1
kukynas Posted October 6, 2020 Posted October 6, 2020 4 minutes ago, MLXXX said: On the other hand, audiophile equipment might well already include chokes and/or capacitors to attenuate incoming mains borne RFI. every modern electronics working with mains voltage should contain input filter and as such should attenuate mains borne RFI no? it's common practice for years... 2
aussievintage Posted October 6, 2020 Posted October 6, 2020 14 minutes ago, MLXXX said: On the other hand, audiophile equipment might well already include chokes and/or capacitors to attenuate incoming mains borne RFI. Yes it might/could/should, and on top of that, the normal processing of the AC waveform to the required DC levels required for operation of that equipment, will also attenuate any noise trying to sneak in. The usual power supply filtering, at various stages throughout the equipment, is very good at removing noise. 17 minutes ago, MLXXX said: If a power cord included small value capacitors between active and neutral (located at either end of the cable), that would tend to reduce the amplitude of mains borne Radio Frequency Interference. You mean like a simple mains filter that you can buy, which also includes counterwound inductors in series with the active and neutral lines to remove common mode noise. Yep
MLXXX Posted October 6, 2020 Posted October 6, 2020 (edited) If testing a low current draw audiophile device for variation on performance with mains supply variations, e.g. a standalone DAC, perhaps it would be useful to power it with an artificially created variable "mains" supply. The RMS voltage of the artificial mains could be varied over a wide range. As that was done, the DC voltage powering the DAC could be measured (though this could require removing the cover of the DAC. For example these readings could be obtained: Mains input voltage, DC supply voltage 250V, 20.15V 240V, 20.10V 230V, 20.10V 220V, 20.10V 210V, 20.05V 200V, 19.01V Attention might then be focused on ascertaining whether the DAC performance varied in the region of mains voltage variation from 240 to 250V. ___________ Another aspect of supply mains variation is the purity of the mains waveform at the power point. Emulating waveform impurity would require a more sophisticated set-up. Edited October 6, 2020 by MLXXX
kukynas Posted October 6, 2020 Posted October 6, 2020 3 minutes ago, MLXXX said: If testing a low current draw audiophile device for variation on performance with mains supply variations, e.g. a standalone DAC, perhaps it would be useful to power it with an artificially created variable "mains" supply. The RMS voltage of the artificial mains could be varied over a wide range. As that was done, the DC voltage powering the DAC could be measured (though this could require removing the cover of the DAC. For example these readings could be obtained: Mains input voltage, DC supply voltage 250V, 20.15V 240V, 20.10V 230V, 20.10V 220V, 20.10V 210V, 20.05V 200V, 19.01V Attention might then be focused on ascertaining whether the DAC performance varied in the region of mains voltage variation from 240 to 250V. this would work in case of unregulated DC for amps stage as suggested at the beginning but it won't tell you anything in case of DACs or other post regulated device where incoming noise and variable V is not the same as on it's output (LDO) 6 minutes ago, MLXXX said: Another aspect of supply mains variation is the purity of the mains waveform at the power point. Emulating waveform impurity that would require a more sophisticated set-up. definitely
bob_m_54 Posted October 6, 2020 Posted October 6, 2020 (edited) 12 minutes ago, MLXXX said: If testing a low current draw audiophile device for variation on performance with mains supply variations, e.g. a standalone DAC, perhaps it would be useful to power it with an artificially created variable "mains" supply. The RMS voltage of the artificial mains could be varied over a wide range. As that was done, the DC voltage powering the DAC could be measured (though this could require removing the cover of the DAC. For example these readings could be obtained: Mains input voltage, DC supply voltage 250V, 20.15V 240V, 20.10V 230V, 20.10V 220V, 20.10V 210V, 20.05V 200V, 19.01V Attention might then be focused on ascertaining whether the DAC performance varied in the region of mains voltage variation from 240 to 250V. ___________ Another aspect of supply mains variation is the purity of the mains waveform at the power point. Emulating waveform impurity that would require a more sophisticated set-up. You're looking too deep again, for power supply voltage measurements etc. The only effect the Power Cable will have on the voltage at the devices power supply input, will be the voltage drop over the cable. The only thing affecting the voltage at the output of the devices power supply with be the power supply design. And the voltage drop will be most obvious for highest loads. The DAC won't draw enough, the Amp would be better. So different approved cables will have very little differences voltage wise. Here's a part of a reply I made to @Benjet with reference to one of the links he posted in the other thread. Quote The "bottle neck" can be represented by voltage drop over the cable, because there is a direct relationship between wire size, current and voltage drop. For a comparison of house wiring (2.5mmsq), to standard 10A flex (1.5mmsq) for a length of 1.5M (on the high side of a standard flex lead) carrying the rated full load of 10A (way more than your amplifier will draw). Standard flex - 1.5mmsq voltage drop at 10A for 1.5M lead - 350mV or 0.15% House wiring - 2.5mmsq voltage drop at 10A for 1.5M length - 210mV or 0.09% So only a 140mV drop "bottle neck" for the standard lead, over 1.5M. And the total loss for the house wiring of say 5M from the switchboard is nearly 710mV, so where's the bottleneck? Note that the house wiring will most likely be carrying a higher load too, if it is a shared circuit, and therfore an even higher voltage drop. - Conclusion - Busted Edit: any difference between two different cables will be in the order of microvolts Edited October 6, 2020 by bob_m_54 1
MLXXX Posted October 6, 2020 Posted October 6, 2020 (edited) 25 minutes ago, kukynas said: every modern electronics working with mains voltage should contain input filter and as such should attenuate mains borne RFI no? it's common practice for years... Yes that is standard practice. It's also been standard practice (for decades now) to derive tightly regulated DC voltage(s) for the internal circuitry of audiophile equipment. Those practices however will not stop some people from trying to attenuate mains borne RFI further, or even installing a mains power regenerator; in the belief such steps may improve the performance of their audiophile equipment. Edited October 6, 2020 by MLXXX 2
Guest rmpfyf Posted October 6, 2020 Posted October 6, 2020 3 minutes ago, kukynas said: definitely Trying to get something w/waveform capture. Trying.
Stereophilus Posted October 6, 2020 Posted October 6, 2020 A side step if i may...? Do any of the technically minded types here advocate for a dedicated circuit for audio mains supply? And if so, why?
aussievintage Posted October 6, 2020 Posted October 6, 2020 1 minute ago, Stereophilus said: A side step if i may...? Do any of the technically minded types here advocate for a dedicated circuit for audio mains supply? And if so, why? Given the short runs in most houses, and the likely impedances of any circuit, it's hard to imagine a dedicated circuit alone having much effect. A dedicated circuit with appropriate conditioning/filtering is a different story.
Stereophilus Posted October 6, 2020 Posted October 6, 2020 2 minutes ago, aussievintage said: A dedicated circuit with appropriate conditioning/filtering is a different story. Can you elaborate? What is "appropriate"? How does it help if the connected equipment is already filtering and regulating everything?
Guest rmpfyf Posted October 6, 2020 Posted October 6, 2020 16 minutes ago, Stereophilus said: A side step if i may...? Do any of the technically minded types here advocate for a dedicated circuit for audio mains supply? And if so, why? From a practicality viewpoint, sure. I can run whatever wire I want and I don't have to wonder what else is using the circuit. I've a three phase mains and solar not on all three phases; I can get one and the other separated. It's easy to meter and characterise if I want to. I can have it earthed however I like within code and even run an isol/bal/trans to it. I would sooner do the above than buy power conditioning in a box (unless I rented or lived in an apartment). Will it likely make a significant difference? Depends on what's in the house/on the circuit/equipment sensitivities/etc.
JB82 Posted October 6, 2020 Posted October 6, 2020 2 hours ago, bob_m_54 said: Yep, that's what shielded power cables do. Handy if you're trying to avoid the power cable polluting near by signal cables. Could this be one possible explanation why people have experienced improvements when upgrading their power cable?
aussievintage Posted October 6, 2020 Posted October 6, 2020 19 minutes ago, Stereophilus said: an you elaborate? What is "appropriate"? Depends on how much noise you need to remove. For very little noise, a simple capacitance filter may be all that's needed, and going up from there to capacitive-inductive filters, ferro-resonant transformers, screened isolation transformers, etc etc, to full power supply regenerators. 20 minutes ago, Stereophilus said: How does it help if the connected equipment is already filtering and regulating everything? It may not help at all in that case. Basic logic, if the equipment is already capable of handling the noise, removing it first won't make any difference.
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