High-res audio comparison: Linn Records Free High Res Samples

[Blumlein 88]

Actually, I'll modify my reply, as I wasn't really addressing the question properly earlier.
If you are going back to the master tape (and just exactly what constitutes a master tape is a whole other conversation) there is a very specific reason to capture at a very high sample rate. You need to be able to capture the bias signal. This is going to be of the order of 150 kHz odd, and depends on the machine and sometimes even choice of tape. The reason for capturing the bias is to allow you to correct for speed variations, and critically, scrape flutter. When the tape passes the heads it scrapes, and just like a finger rubbing the rim of a wineglass you can get very fast changing modulation of the speed of the tape past the head. This leads to a form of intermodulation distortion that is welded into the tape at the moment of recording. If you can see the bias signal you have what amounts to a local clock embedded in the tape that you can use to deconvolve the flutter. If you have the luxury of finding the original tracking tapes you can recover real audio that nobody has ever heard since the day the track was laid down. Even if you only have access to the master tapes, you still have a chance to remove the last generation of scrape flutter.

So this is another issue with these high res releases from old tapes. It would appear that most have not taken advantage of this possibility, and thus have actually lost a real opportunity to crete a better quality release, and have simply been lazy and depended upon woo to justify what they are doing. Proper forensic analysis of the tapes and modern processing would have yielded a conventional 16/48 result that exceeds the real musical information available in the silly lazy money grubbing stuff they are actually pedalling.

I forget the name of it, but there is some software which does what you describe. There have been a few releases of older recordings after having been cleaned up with this. Wow and flutter gone among a few other tape artifacts.

 

[Francis Vaughan]

Another issue nobody ever mentions is that air has a very brutal frequency dependant absorption of sound. Even at human frequencies this matters. But when you get to ultrasonic frequencies it becomes silly.
At 3 metres, at 40kHz the air alone has pulled about 4dB out, and at 100kHz this rises to closer to 10dB. Which is simply domestic listening distances. Attend live music and you are looking at way higher attenuations. At say 10 metres, which is pretty close for many venues, 40kHz is about 12dB down. 100kHz is of the order of 40dB down.
Simple conclusion. At live music events, there is even less justification for claiming that anything above 20kHz matters. Indeed stuff below 20kHz starts to suffer for no other reason than the air is absorbing the energy. Close micing of instruments removes this during recording, but if the intent is to reproduce the experience of live music, which is the usual claim, it is doing exactly the opposite.

 

[Deleted member 22141]

This series of videos is fantastic.

Surely there is no point at all to playing back anything above 22KHz? If your system is well designed the higher frequencies won't harm it, but if it's not well designed then it might?

Why would you want the amplifier or speakers to try to reproduce frequencies we can't hear?

Qobuz doesn't seem to have an option to "downgrade" to CD quality only. I think once Spotify starts their 16/44 service I will simply use that.

 

[scooter]

Thanks for your replies gentlemen. Another question, is there any proper way or software to allow us identify if the digital audio samples we have are "coming" from the original masters or not?
I think there should be some mandatory certifications/regulations implemented for digital music content (like a vinyl pressing mentioning they're from an original master), just adding HiRes or HD sticker says nothing...

 

[Count Arthur]

How many files have you tested so far Amir and have you found any good ones yet?

I think you've covered 10 or more in the videos and so far, not one has been without issues.

Also, does anyone know of a free equivalent to Adobe Audition?

I'm curious and would like test some of the Hi-Res files I have, but not curious enough to pay Adobe prices. Before Adobe bought Dreamweaver you could buy it outright for about £200, now its £240 a year.

 

[xaviescacs]

So far all these videos demonstrate various shortcomings with HD recordings. Are there examples of well made, pristine HD recordings with music content above 22 KHz?

Yes, there is plenty. I think amir is not claiming that there are not good hi-res recordings. Instead, he is showing that not all hi-res recording deserve this name and he is showing how to check that by ourselves.

 

[xaviescacs]

Also, does anyone know of a free equivalent to Adobe Audition?

https://www.audiosciencereview.com/...s-cd-2l-sampler-comparison.23172/#post-772800

 

[Newman]

I guess the "analog sources" he's speaking of are the instruments / vocalists, they won't become digital

Well he wrote "original mastering from original analog sources". The instruments / vocalists don't go straight to mastering: they get recorded, then mixed, and only then to "original mastering".

Also, not all instruments are analog these days. Some have, indeed, "become digital". Get with the program!

cheers

 

[amirm]

How many files have you tested so far Amir and have you found any good ones yet?

It is time consuming to check so I have not tested many. Probably 5% of the high-res content I have. But yes, there are clean ones which I will post in a future video.

 

[restorer-john]

If you are going back to the master tape (and just exactly what constitutes a master tape is a whole other conversation) there is a very specific reason to capture at a very high sample rate. You need to be able to capture the bias signal. This is going to be of the order of 150 kHz odd, and depends on the machine and sometimes even choice of tape. The reason for capturing the bias is to allow you to correct for speed variations, and critically, scrape flutter. When the tape passes the heads it scrapes, and just like a finger rubbing the rim of a wineglass you can get very fast changing modulation of the speed of the tape past the head. This leads to a form of intermodulation distortion that is welded into the tape at the moment of recording. If you can see the bias signal you have what amounts to a local clock embedded in the tape that you can use to deconvolve the flutter. If you have the luxury of finding the original tracking tapes you can recover real audio that nobody has ever heard since the day the track was laid down. Even if you only have access to the master tapes, you still have a chance to remove the last generation of scrape flutter.

So, just out of interest, how are going to capture the bias signal on a tape made on a deck you don't have? Are you telling me the there are stationary playback heads on open reel decks that can successfully read a 150kHz bias/erase signal? And the bias signal isn't exactly crystal locked in the first place. How reliable would it be as a form of clock even if you could read it?

Tell me more about this process, I am interested.

 

[restorer-john]

It is time consuming to check so I have not tested many. Probably 5% of the high-res content I have. But yes, there are clean ones which I will post in a future video.

Have you (or anyone else) come across so-called high-res recordings with diabolical or dangerous high level spuriae outside the range of human hearing?

In other words, tweeter or amplifier killers embedded in a "hi-res" recording? I've often thought that would be a potential trojan horse attack for audiophiles to kill their expensive tweeters or make their amps oscillate.

 

[scooter]

The instruments / vocalists don't go straight to mastering: they get recorded

Well actually that's what I meant, they get recorded at what resolution and sample rate? To my understanding one needs to use the highest sampling rate to capture maximum information from an analog signals at a given time. Then down-sample as I don't see any advantages in distributing high res content and charging a premium price also (at least based on what I'm seeing here in Amir's reviews).
Regarding digital instruments, if you mean USB mics then I don't think pros are using them to record vocal tracks. If they did then there should be some high quality mics with proper ADC inside them.

 

[Deleted member 31750]

This is the last video I had stashed form back in 2017 when I did these high-resolution audio comparisons against standard one using the same master:

After this, I will be producing new ones.

The conclusion is that is disappointing for the pointed out distortion/noise in the frequency band. Is disappointing the recording or the nature of HiRes audio format?

 

[respice finem]

"digital instruments" = things like synths and such. The original recordings are AFAIK done mostly with 24bit/96kHz at least, not necessarily even to "capture the most..." but simply to have more "headroom". https://en.wikipedia.org/wiki/Audio_bit_depth
Anyway, to issue a CD it has to be red book compliant, so 16/44.1 https://en.wikipedia.org/wiki/Compact_Disc_Digital_Audio#Standard

 

[scooter]

tweeter or amplifier killers embedded in a "hi-res" recording? I've often thought that would be a potential trojan horse attack for audiophiles to kill their expensive tweeters or make their amps oscillate.

How modern AVRs are acting about this? Do their internal DACs use sharp filters cutting all above 22 kHz? Or is there any operation mode that passes a whole band to the amps and then to speakers (maybe Pure/Direct modes used intentionally with digital files rather than analog inputs)?

 

[Francis Vaughan]

Are you telling me the there are stationary playback heads on open reel decks that can successfully read a 150kHz bias/erase signal?

If the head wrote it, it can read something. Needless to say one will need to get the alignment perfect. You may need new wide band head pre-amplifiers, and a bit of general care with the electronics, but there is no intrinsic reason why the bias can't be recovered. It does not need to be recovered at full level, just enough to get a meaningful level of phase accuracy. Obviously the evil mix of all the weird physics that is tape recording folds into the final response and recovery. Head gap and tape speed clearly dominate the question. But the cut-off isn't brick wall. Proof of the idea is that it does indeed work and has been used successfully.

The bias frequency doesn't need to be ultra accurate, just noise free enough that over the the periods we are interesting in (of the order of the period of the scrape flutter) it is stable enough to allow deconvolution of the intermodulation. You could probably usefully track the bias with a digital PLL if there was some worry that there was meaningful longer term drift.

 

[scooter]

"digital instruments" = things like synths and such. The original recordings are AFAIK done mostly with 24bit/96kHz at least, not necessarily even to "capture the most..." but simply to have more "headroom". https://en.wikipedia.org/wiki/Audio_bit_depth
Anyway, to issue a CD it has to be red book compliant, so 16/44.1 https://en.wikipedia.org/wiki/Compact_Disc_Digital_Audio#Standard

This is from the link below, interesting...
Quote
"Some CDs are mastered with pre-emphasis, an artificial boost of high audio frequencies. The pre-emphasis improves the apparent signal-to-noise ratio by making better use of the channel's dynamic range. On playback, the player applies a de-emphasis filter to restore the frequency response curve to an overall flat one. Pre-emphasis time constants are 50µs and 15µs (9.49 dB boost at 20 kHz), and a binary flag in the disc subcode instructs the player to apply de-emphasis filtering if appropriate. Playback of such discs in a computer or 'ripping' to wave files typically does not take into account the pre-emphasis, so such files play back with a distorted frequency response".
Unquote

This brings the next question, is there any CD ripping software that keeps pre-emphasis information?

 

[Newman]

not many CDs, IIRC, are pre-emphasised.

 

[respice finem]

AFAIK no label uses it nowadays any more for their CD issues, and all "contemporary" players (including PC ones) apply de-emphasis for their output, when the bit set for it is detected. If you're unlucky and your player/ripper wouldn't apply de-emphasis, you are unlikely not to hear it. Having ripped north of 1000 CDs, I've never encountered this.
What may happen, is master tapes encoded with Dolby A, later digitized without decoding Dolby A - they will be treblish, this was sometimes even applied as an "insider trick" to boost "spaciousness". https://www.audiothing.net/blog/the-dolby-a-trick/

 

[Newman]

If the head wrote it, it can read something. ...

I think he was asking about the digital mastering studio accessing an old tape on (clearly) a different deck to the one used for original recording.

I suppose the idea is that the studio has a high quality machine, and tuned to within an inch of its life.

P.S. the bias tone was often more like 50 kHz, but over 100 kHz was used, certainly