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In Reply to: RE: Spectrum Plot for CD rip and 24/96 download - pics posted by AbeCollins on July 11, 2014 at 15:18:26
Same bump in first 60 seconds of 24/96 recording from vinyl.
Follow Ups:
You sampled the first 60-secs of the track. I actually started 30-sec into the track, then grabbed the 60-secs after that.
I think that blip is probably throughout the recording.
"I think that blip is probably throughout the recording."
I agree. The first 1 min 45 seconds is relatively quiet, as is the last 30 seconds. The bump appears in all the samples I took from those periods. It gets covered up during the loud portion of the song.
However, I didn't hear anything I would attribute to that 28.7k bump. Led Zep I and II both sound great, better than the CDs I had. I also attribute the improvement to the mastering. Just got III yesterday. Haven't listened yet.
I have no idea what that 28KHz anomaly might be. It's strange that it exists in a number of 24/96 tracks not only on one album but at least a couple unrelated ones from different artists. I viewed this on a Led Zeppelin album and also on The Doors, both from HDtracks. It would be interesting to see if the blips exist on downloads from other vendors.
I hope someone figures it out. We're all just guessing at this point. Bizarre.
My Led Zeppelin is on vinyl that I recorded at 24/96.
I also found the same blip on other vinyl I've recorded. Not all but a few, leading me to believe it's not added by my equipment.
One was a 1979 recording by Jean-Luc Ponty that I purchased the year it was released.
That is just plain weird. Wonder where that 28KHz blip originates.
That's too bad. I wonder if the problem is with the original analog masters. Hope not, since then there'd still be hope someone could do a noise free high res rip.
Hey, I'm fine with the blip. I just don't look at the graph while listening to the track. It sounds quite good IMHO. ;-)
I am one of those customers you hate to get I guess. Back ~ christmas '06 I IIRC I took my first "1080p" tv back after I discovered it only upconverted to 1080p and couldn't take and display 1080p source material. 1080p printed all over the box. That's why I bought it and how the sleazball sales dude sold it to me. I didn't figure it out until I got it home and couldn't get my new at the time PS3 to send it anything but 720p. I probably can't see the difference from my seat with the screen size that fits in here. It is the principle of the thing that bugs me.
Edits: 07/12/14
So those 28kHz blips (@ -100dB on the scale, IIRC -72dB on Abe's) are hurting your listening experience? I guess you also sleep during the day and I really don't know how you're reading this forum, but your typing is excellent considering. :)
Edits: 07/12/14
That noise is a symptom of something wrong. It should not be there. Without understanding the root cause it is impossible to say whether there is a sonic problem. I have transferred a bunch of old master tapes and it's been my usual experience that ones with funny noise peaks on them don't sound as good as clean ones. Usually, filtering out the noise peaks makes things somewhat better. But the best recordings don't start out or gain these unwanted artifacts.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
The peak is -60dB down compared to what is in the 0-1kHz rangeso it is questionable whether one can hear it. There are both masking effects and ear sensitivity going against audibility. Given the age of most audiophiles (or Jimmy Page), the odds are further reduced. I agree it would be more satisfying to know that this noise pollution was not there, but that would be listening with one's brain, not one's ears.
A quick experiment: upsampling the 16/44.1 to 16/96 or 24/96 and listen whether this upsampled file gets to sound as good as the "orginal" 24/96 remastering. As you pointed out earlier,one benefit of higher sampling frequency files is to move reconstruction filters to much higher frequencies than what is otherwise possible with 44.1kHz. Nothing to do with the actual file content.
One caveat: we do not know how much high frequencies these hires remasters contains because the posted spectra have been averaged over 60 seconds. As otherssuggested, it would be more informative to see spectrogram to see if there are times at which there is much more high frequency content in the high res file than in the CD file. It is not like Bonham never hit the cymbals!
Normally, I use a 65K FFT for spectrum averaging. But my software allows other sizes as well, plus different windows. (Soundforge 10). I also have iZotope RX and this includes a spectrum plot of time (X) vs. Frequency (Y) vs. intensity (Z, i.e. color). The size of the temporal resolution can be adjusted but there is the inescapable tradeoff of time resolution vs. frequency resolution.
With these spectrum plots it is very easy to see high frequency noise and to distinguish it from high frequency musical sounds. In addition, one can edit the spectral plots to easily remove unwanted noises, even to the point of removing notes out of a chord or removing guitar string squeaks.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Unlikely your software will allow to do a FFT with 60*96,000 points. There's a bunch of averaging going on that's a function on how the analysis is setup (number of points in the window, window overlap,...) The loss of frequency resolution that comes with shorter windows does not matter since energy gets summed up in each frequency band. A delta f of 1Hz or of 10Hz will still tell the story of whether there's significant energy at higher frequencies.
It looks like you posted in the wrong place.
I agree that it's unlikely that Abe Collin's FFT averages over 60 seconds. Possible, but not likely. I know that my FFT averages over 65K points with my usual settings and this corresponds to about 2/3 of a second at 96 kHz. The points in the window are weighed with the central points counting more according to a formula that smooths out the plot. I generally use a Blackman-Harris window.
There are a lot of other issues involved with interpreting FFT plots, such as "FFT gain" which is a measure of how the noise floor varies in FFT plots according to the window size and window type. If Abe wanted to, he could calibrate his FFT gain by creating a test file with a 28 kHz tone and adjust the level of this tone to where the FFT shows it at the point on the suspect download file. A little knowledge can be a dangerous thing, but I'm confident that Abe Collins knows enough to figure these things out, if he hasn't already done so.
BTW, I have other software that I use that uses 8 million points. I've used this to do convolution by transferring to the frequency domain and multiplying. In addition, my player routinely does convolution at 2.8 MHz sampling rate with a time period of about 1 second (over 2,000,000 samples). I presume the software uses FFTs, to avoid the necessity of more than 10^14 multiplications per second using a simple time domain approach, which even if my hardware could do would run up a huge electric bill.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
between Abe's and rrob's samples. It probably accounts for the spike level difference between the two if it is indeed the same spike.
Since my system can sustain a plus 120dB sound at my listening seat per my metering, those would be pretty loud to nearby dogs assuming my system actually responds to them directly and I actually chose to listen at that level. It could happen since it is Zeppelin after all. :)I think my biggest concern is the wasted effort and resources in the system trying to reproduce something that isn't part of the intended program. It will always be damaging at some level, but obviously hard to quantify without some appropriate test gear what level that damage is.
Rational or not I'd spend money yo ensure it isn't there in the first place. It's just bad form to have a -72dB spike in 24/96 files presumably coming at a cost premium.
Edits: 07/12/14 07/12/14
Yeah, I know where you're coming from, but I bet there are bigger battles to fry :) re the recordings' other "failings". (If there are any, besides that they should be from an analog source on LPs, or 192/24-32 etc. etc.)
I wonder if the noises are artifacts from the original masters' tape devices, or from something previously recorded on the tape and poorly erased (it apparently sometimes happened back then). I have no idea.
I guess it would be worthwhile to check out the original LPs and speculate after that, but probably any 28kHz if it could even be on there would be ground away by now on mine, and I always took/take good care and used half-decent carts even when I was a teenager.
Vinyl made from 24/96 master??
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
According to the Analog Planet article, they were 24/96 masters.
My recording of the vinyl was made at 24/96.
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