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  1. Great to see a really specific, very concrete, audible report like that. (As opposed to the more common subjective reports seen such as, "this power supply provides a lowered noise floor", or "a blacker sound", which could leave one in doubt. ) It's understandable that with a very low output cartridge even a very small amount of interference can become noticeable. I guess the physical placement of power leads near the turntable could become critical - the further away the less likely to interfere.
  2. What model is this? I presume it will monitor the incoming AC for voltage and frequency. Will it also capture harmonic content and/or general "hash"? It is not the same as locally generating an AC supply, which is what I had in mind to really pin down that variable. On the other hand using the actual mains allows the ingress of hash (at whatever level and in whatever form it may take from time to time at the power point in use, at the test site), and that hash one suspects is a potential trigger for aberrant device output and possibly the reason some audiophiles have
  3. I'm merely trying to avoid the exercise getting bogged down in trying to find correlations of the output waveform with one variable (changing the power cord) that are "swamped" or confounded by the presence of other variable factors. The further down into the noise that you try to look for correlations, the more time consuming the task and the greater the risk of false positives. If there is a desire to drill down to data variations at the limits of resolution of measurement devices, then it would become important to hold as many of the variables constant as possible that are no
  4. Studies involving the relative efficiency of audio codecs often do not go much beyond 128kbps because the more efficent codecs at that bitrate are approaching transparency for a large percentage of the population for most of the time. Here's an example: of a compilation: (There are many other similar compilations in graphical form or tabular form, on the net.) If you read the literature in this subject area of audio codec transparency you will find it reported that at 256kbps even trained listeners will typically strain to hear any differences wher
  5. I don't understand the relevance of the above to this thread. It is clearly not relevant to an audiophile how the silence between CD tracks "sounds", because with a properly operating system they should hear nothing from their speakers at ordinary gain settings, when they are in their listening chair (not with an ear pressed against a speaker enclosure!). To then proceed to conjecture that very low level signals commensurate with system noise may become audible if piggy-backed onto an otherwise audible signal (e.g. onto the sound of a vocalist singing, or a piano being played) is a thought.
  6. Could you clarify what you mean here by the description "content above the floor"? (I note it is well known that low level content is often masked if much louder content is present at the same time.)
  7. I mentioned a number of them in my lengthy post of last night:
  8. It is an indirect approach in the sense that the test scenario in contemplation includes multiple other variables that are not being held constant. A direct approach would attempt to hold other variables constant as much as possible. I agree that measuring the audio signal output is a direct approach, of itself.
  9. Let me puncture the "resounding silence" with a comment. As I explain below, in its context this thread seeks to devise a measuring method suitable for revealing marked differences of interest to audiophiles. If after applying the method so devised, no marked difference is found, that I suggest is a sufficient outcome for the purposes of this thread. (It would be somewhat superfluous to mention that minute differences might not have been revealed in the testing That applies to any measurement exercise.) The audiophile does nor care if, say, the amplifier gain is changed one part in a millio
  10. Sounds like you might have "saved" [creates a high level Audacity summary file] rather than "exported" [creates an actual audio file].
  11. When you get it back you may find it is no longer sensitive to power cord differences. Ah well.
  12. For heaven's sake, rmpfyf, simply record the output of your killer DAC with whatever ADC you have on hand, if that is truly your goal. For such an obvious audible difference in sound, you should have no trouble finding a difference in a recording even using a 16 bit 48kHz ADC. And record just a single channel if you don't have a stereo ADC handy. Then upload file A [using original power cord] and file B [other power cord] for us all to hear! This should not involve rocket science to achieve, if the difference is as severe as you have reported. I
  13. There's no accepted limit for the point at which newspaper headlines become illegible because of insufficient contrast, insufficient illumination, or lack of clarity in the font design or the spacing of the characters. However we readily accept that at a distance of 10,000km the headlines will not be readable by a naked human eye. It is only when dealing with stimuli around the threshhold of human perception that it becomes important to tease out the precise limits of perception, and investigate further. Obviously, time spent testing 100 subjects for whether they can re
  14. Indirect vs direct testing - a hypothetical example Assume that 10 years ago a retirement village had concrete driveways constructed for each of the 100 villas in the complex, and that 10% of the driveways were constructed with additional steel reinforcing because those driveways were intended to be available for use by heavy machinery. Assume also that all relevant records identifying which of the driveways have additional reinforcing have been lost in a flood. Two competing plans, A and B, are under consideration for determining which driveways are in fact the ones
  15. By way of explanation, my reference to a specialist DAC here was to this thread's Original Poster's "killer" DAC which according to @rmpfyf produced very obviously impaired sound when a power cord was connected that was not the original. I took this assessment of a drastic impairment at face value and expressed the opinion that it might have been due to the device (which uses valves) launching into high frequency parasitic oscillations, an occurrence that was not uncommon with valve radios in the mid-20th century. Circuit layout was critical and moving wires in the radio just a small distance
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