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  1. In audio circles it is known as an earworm.
  2. Never mind the above files. There is a mistake. I'll fix it and repost later. Sorry.
  3. Here is a reprise of a short simple listening session. You can download these two zip files. Each will open into three 30 second snippets of music. Two are the digital originals. One is a copy sent thru a DA to AD stage. Tell me which one is the copy. The odd man out. It should be easy as the ADC is a very inexpensive unit. Or you can say you cannot hear a difference. https://www.dropbox.com/s/sswuh8boaj6x9ze/Fiona Apple.zip?dl=0 https://www.dropbox.com/s/0jx0nv44ms0ddbo/Hyperion Knight.zip?dl=0 I don't want to pollute this thread so please PM me with your results.
  4. I would like to have seen the inclusion of the original file without it being labeled as such. Might have been surprising if it had been included.
  5. I was looking at this some more. I'd said if you reduce levels on the sweep by 1 db it cleans up. Actually even reducing it .1 db from full max makes all the nasty behaviour above disappear. So it would be clean other than when max level occurs between 21,750 and 22,050 hz. That is not going to be very common. Yes, the Forte would be better designed not to act that way.
  6. I don't think the class D amp would do this. It wouldn't be aliasing. Most now have a switching frequency of around 400 khz. They have filters on the output to filter most of this out prior to reaching the speaker. They'll have good response to 40-50 khz usually. Some are on up to 100 khz. But as the switching noise is the last thing prior to the speaker, and the speaker isn't going to respond to it you shouldn't see anything from it.
  7. Yes, I noticed the frequency bump in the upper few hundred hertz. Quite a bump too like 3 or 4 db. And that even at 192 khz the interaction with the 31 khz tone is still there. I liked it mainly because it has some nice quiet high gain microphone preamps. Good when I occasionally use ribbon mics. I've been doing room acoustic measurements with a calibrated USB mic and REW. All you need is the mic and a laptop. The built in ADC seems to effectively be 16 bits worth, but for in room measures that isn't much of a handicap. Have considered one of the Sound Devices Mixpre units when I want portable use of other microphones.
  8. This is unusual behavior. It only does this at max level and between 21,750 hz and 22,050 hz with the Forte I have. An ADC shouldn't let such signals thru, but the Forte shouldn't act that way. Tried another DAC and it does none of this. However, if you drop the signal to -1 dbFS that goes away. I suppose you've noticed the 31 khz tone around the PSU, also causes faint aliasing in the ADC not around Nyquist, but around the 31 khz tone. Making me wonder if that is from the PSU. Here is a 48 khz and then 96 khz sweep recorded at 192 khz.
  9. Not for me as I've said. I'm not against correcting measurable problems. If upsampling fixes the issues then good, but it would be nicer not to need that fix.
  10. Okay so how does the imaging of the RME show up where we can hear it? And I will say if someone is saying they can hear such things at -120 db they'll have to prove it. I'll say I don't believe it for all 7 billion people on the planet. Just like if someone says no one can say how fast they can run and they claim to run the 100 meters in 7 seconds.
  11. No, I've said I don't have an ADC that does above 192 sample rates. So I used one at 192 khz for a DAC playing I think 48 khz. So yes, I can't see imaging like the RME you show. Now okay the RME has some imaging at -46 db. Where do the results of that show up in the audible band. We can all suppose it might show up somewhere. And we can't definitely say it doesn't until you check it. But at that level if IMD from the amp it would have to have a very poor 1 % imd for it to show up back at 2 khz at -86 db. Is it possible with some amp? Sure. It is a problem for most good amps? I don't think so. Most amps that have that kind of bandwidth will have low IMD and especially for a -46 db pair of signals. It is going to be lost in the noise and then some.
  12. You used something with MQA filters? I mean we know those are leaky. Not typical. And for that reason not a good example. Can you have leaky filters than muck up the results? Sure, I never implied you couldn't. Here are some for the Forte, which I think you also have. This spectrogram goes to gray at -144 db. You see an idle tone which is in the Forte DAC at about 31 khz, -95 db in level which isn't great. You see double that frequency at -125 db. Otherwise no imaging above -144 db for 2hz-20khz. On the 2hz-40 khz sweep, you get a little imaging just above 20 khz at about -132 db. It gets a little higher in level as the frequency increases, but never exceeds -115 db. This is not a perfect result, but there is not a whole lot up there to 96 khz at least.
  13. IMD would show up even if the ADC is running at 44.1 khz. You don't need wideband measures for that. So whatever the ultrasonic sources of IMD into the audible band you'd already be seeing them. They aren't much apparently. The reason I don't record such things with DSD256 is I don't have an ADC for that. So I'm limited to 192 khz. That doesn't mean nothing above that can't matter, but I'm incredulous it matters much if at all. I'm not worried if something shows up at -120 db, because you'll not hear it. It is not perfect, but it also isn't an audible problem. The things I showed earlier may have been aliasing only. I've done the reverse test for imaging as well. Similar levels were seen. My test signals were all at max level. And I believe I described the limits of the spectrograms. So they aren't meaningless.
  14. I don't agree with you here. If the hearing is the bottleneck of bandwidth, and it is, then you don't need all the frequencies that are above a noise floor out to some megahertz range. You end up with differences that make no difference. Analyzing the bandwidth needed in such a case would indicate 96 khz sampling is enough with quite a margin for safety. Do we need to sample up to optical frequencies because the glare of a spotlight on the horn of a trumpet will shine across our ears and make a difference?
  15. So what are the effects of an image at 300 khz? The amp likely won't respond much usually, the speakers won't for sure. Our ears don't care much about phase at higher frequencies. Well not the way it works. The 90 db or so I've seen from 192 khz, is with a single tone max frequency. Get multiple tones or noise and max total signal is still much lower at a given frequency and much lower in what images across it. Way below the noise floor of any gear for the most part. No I simply don't wish to chase more ghosts that are smaller than the angels dancing on the head of a pin at great complication, expense and no benefit to human ears.