"Hi-Res" recordings... part 3 (the Vinyl revenge...)

Okay... so now it's time for the turn of the vinyl.  For a while my LynxTWO has been out of action (the input stage has failed multiple times over the past ~14 years, quite annoying on such an expensive card... it will eventually get fixed again one day when I can be bothered...), so I had to press the E-Mu 1820M into action instead.  The noise floor is slightly lower than the Lynx, but the distortion is slightly higher.  Still plenty good enough to be compared to the other sources, as it uses good quality AK5394A A/Ds.  I will be using my old John Linsley Hood shunt-feedback phono stage, powered off the original power supply.

For a while now I've been using a Lyra instead of the Shure V15VxMR with JICO SAS stylus... while the V15+SAS is a superb combination, as is often the way with audio, when you hear something slightly better, it's hard to go back.  The Lyra has a very wide frequency response as in common with most high performance Moving Coil cartridges... the distortion is also very low, I have measured it to be lower than the Shure, which is somewhat more unusual for a MC.

I recorded each track, and then resized as best I could, matching the RMS power to make it a representative test.

First up is the 4Beards reissue, 4M101...

You can immediately see that there is a lot more transient energy above 22K (as in, it actually has some) than with the HDTracks download.  The mix and sonic tone is very similar to the HDTracks... next I took out my early copy of the Atlantic LP, SD8139.  It isn't in perfect condition, but it's very hard to find a mint one these days... the cut is almost identical in loudness to the 4Beards reissue, but the band compression seems to be slightly different.  Big difference in frequency range...

Okay... that's a lot more going on at the top!  Mix isn't quite as spacious, but there's a bit more bite to it... I guess that's due to the extended top end.

Comparing all of them in the 10K-40K range across the whole track...

But it becomes most obvious when you zoom into a small space in the music....

... just how much information the so-called "Hi-Res" version of the music is lacking.

So all I can really say is, buyer beware... my own recommendation is that unless you can be certain of the provenance of the high resolution material, you are better off finding a good pressing of the vinyl.  If we consider the 4Beards reissue for a moment, for me it sounds better than the "Hi-Res" from HDtracks and is actually about the same price to buy.  And you get a real "thing", which you can keep or sell at your leisure.

So why bother with the download?  Good question.  Convenience might be a reason, but bear in mind that you can get a CD of this album which you can rip in a few minutes, and by all accounts will not be inferior to the 24/192 version - at the time of writing this, there's a copy for 3.46GBP on eBay.

I'm getting my hands on an early version of the CD and will compare it to the 24/192 HDTracks in due course, but I think we're done with the surprises for now... :)

"Hi-Res" recordings... part 2

So I headed over to www.hdtracks.co.uk for the first time in what was a very long time... so long in fact that my account had been quietly closed!  Would have been nice if they'd mentioned that.  In any case, the reason I had stopped visiting is due to licensing restrictions... I couldn't buy anything I wanted to buy as it wasn't available in the UK.

Nice to see it has been sorted out, the vast majority are now available.  So I purchased a handful of albums, at considerable cost... most of the albums in 24/192 seem to be priced around 18GBP - for a well known classic, you could probably pick up a second hand CD in the region of 4-5GBP, so this is quite a premium for the privilege of downloading a few files.  The 96kHz downloads are slightly cheaper, but I wanted the 192kHz for downsampling tests with FinalCD.

I listened to the albums I knew well, and I have to say that I was somewhat underwhelmed.  I have encountered this with "Hi-Res" recordings before, as I said in Part 1... there are a couple of reasons why this may be, but they weren't awful by any means.

In particular, I listened to Aretha Franklin's "Never Loved A Man The Way I Love You" in 24/192... it sounded, well... pretty poor.  Maybe not a great recording.  The 4 Beards vinyl version I have was not quite as rough.  So I went and had a look at the FFT for track 1...

Not a lot happening above 22K or so there... what about an average across the whole file?  You wouldn't expect it to be perfectly flat as that implies random noise which will cancel out...

Hm.  Nothing.  At all, just noise with a few idle tones.  I had a look through the whole file and there's nothing up there other than noise and a stray tone, centred on 76.8kHz, presumably from the A/D converter.  Here's the spectral, focusing on the 10K-30K band...

Hm.  Not looking good.

There's no question in my mind that this has been A/D'd at 24/192, the noise floor is too strange to explain otherwise.  What is rather open to question is what was the source feeding the A/D converter.  For an analogue converter to brickwall like that would highly, highly unusual.  I checked all the other 24/192 recordings I bought, and there was nothing like this... for example... Joni Mitchell's All I Want...

... looks natural and genuine.  Of course it is possible to "fake" a Hi-Res recording but the Aretha Franklin looks to me like it could have been taken from a CD source... and if so, a slightly ropey D/A at that, one with a very high noise floor, given the low pass filter visible in the noise floor.  That might would suggest a 1-bit converter from the mid 90s... or it might just be a very noise reel to reel tape, who knows.

I contacted HDTracks to complain, and their response was disappointing at best.  They pointed out that they do not record or master the tracks, no-one else had complained about the album, and that if I had a problem, to take it up with the record company.

I pointed out their page about Quality commitment, which drew silence.  It seems they are very happy to take your money and then point the finger at someone else when a customer questions the quality being offered.  I find it hard to accept that the Aretha album can be called "Hi-Res"... either the master source simply has no content above 22kHz (which I suppose could be possible) or the source for this "high-res" master is actually a 16-bit 44.1kHz or 48kHz digital copy which has been played through a poor quality D/A and captured in 24/192 to pass HDTracks' "quality tests".

Even a cursory examination of the spectral analysis should have flagged this up (which HDtracks claim to do in their Quality commitment page), so it is clear that HDtracks do not vet their files very carefully, despite what they claim.

To try and get to the bottom of this, I'm obtaining some early vinyl of this classic album to see whether there really isn't a version out there with content above 22kHz... it will be interesting to find out!  I also have an early Japanese CD version of the album coming to compare the general sound quality with.

Something to bear in mind - when you pay for downloaded music, you have nothing to "sell on"... if you are not happy, you may be lucky and get a refund.  If not, you would appear to have little recourse.  It seems to be known that the "quality tests" at HDTracks have varied results - I doubt they are unique in this as they do not generate the material, only sell it, but some baseline of quality was to be expected from a company coming from Chesky...

I do hope these companies start to take quality a little more seriously, as it rather undermines Hi-Res downloads as a whole and will eventually unravel their massive margin when people realise they a) can't be sure if they are getting something better than CD quality and b) they are left with a rubbish bunch of 1s and 0s and a hole in their bank balance...

Frankly, rather than spending 18 quid on a download, get a decent physical pressing of these albums on Vinyl, where possible.  It may cost slightly more, but you will have something which you can enjoy, something you can touch, and in a lot of cases something which will actually retain value.  Your downloads are worth $0 once you have paid for them... !

"Hi-Res" recordings... part 1

I had been hoping to get the wedding blog post series done by now, but as usual life/work gets in the way... time for an audio intermission... !

Some of the viewers of this blog may be aware that when not at my full-time job, I spend rather a lot of time working on audio... way back in, crikey... must be 2001, I was commissioned to develop the software for the Zero One Ti48.  This was one heck of a way to do my first commercial product, and is where I really cut my teeth on doing practical, high quality audio DSP, after my dalliance with digital crossovers back at university.

In some ways the Ti48 was way ahead of its time.  It allowed you to rip CDs to an internal hard drive back before the concept of a music server had materialised in general use.  While it may have been based on a PC architecture, and it was criticised in some quarters because of that, it was to misunderstand the work that had gone into the concept and how the quality was far beyond what a typical "PC player" could achieve and could offer truly "high-end" sound quality, through a combination of the right hardware and software.

One thing that was particularly unusual about the Ti48 as an audio transport was its ability to play up to 192kHz material.  The only problem was that back in 2002, there wasn't any 192kHz material to play!  Audio A/D converters capable of doing 192K back then were rare, and probably custom designed, or re-purposed from another intended use.

96kHz capability had been around for much longer, probably hitting the mainstream back in 1993 with the Pioneer D-05... I do remember when this came out, and it seemed very exciting to be able to cover well beyond the hearing range to allow for improved digital processing and avoid the hairiness in the top octave - the reviewer marvelled at how much more natural the tape hiss sounded...  It took a lot longer to make it to other recording equipment, though...

While it was very cheap to make an existing 48kHz delta sigma A/D do 96kHz - you just do less decimation at the end... this wasn't really optimal for performance as you ended up with a lot of shaping noise where your new octave was meant to be.  It really required a redesign of the modulators and in some cases faster bit clocks to achieve a "true" 96kHz performance, but the potential was there.

This came in very useful for the advent of DVD... you may ask why?  Because DVD was the first "HiRes" digital format in wide public consumption... the story goes that the chaps at Pioneer managed to sneak in 24-bit 96kHz support to the official DVD specification... given their previous form with early 96kHz products, this makes a lot of sense - they felt it was beneficial, and having the main delivery format for films supporting it would put a huge number of players out there.  Very wise. 

Players were not forced to play 96kHz directly as I recall (they were allowed to downsample to 48K) but all must be able to play a 24/96 disc.

I got my first DVD drive in perhaps 1998 or so from Creative... it was bundled with a big Dxr2 MPEG2 decoder card, as most PCs of the time were too weak to be able to decode smoothly by their own.  Standalone DVD players were still fairly expensive at this time, so adding one to a PC was a reasonable solution for DVD watching.

At the time, I wasn't aware of the 24/96 capability - I was mostly buying it to watch films in a quality never encountered before at home... but some people were looking into what was possible...

One in particular was David Chesky... Chesky Records (along with Classic Records too) put out some of the earliest 24/96 DVD-Vs... these basically consisted of a static video frame which was then followed with pure 24/96 audio... DVD couldn't guarantee the bandwidth to offer more than 24/96 stereo in PCM, but this was a massive step up technically from what was available in the past.

Playing one of these discs on a computer used to be a proper pain in the backside.  What I ended up doing was extracting the raw data from the VOB files and then running a bit rearranger as the samples were packed into a strange order - this was worked out through trial and error on my part!  Then I had a normal 24/96 WAV file... while I had been able to record 24/96 since 1999, this was my first opportunity to see what a professionally recorded hi res recording looked like... indeed, on the FFT there was life above 22K after all!

While most large diaphragm microphones struggle to remain flat, there is still plenty of energy going up there particularly for impulsive/percussive sounds, and while we may not be able hear these through our ears very well (bone conduction is another matter), humans are remarkable at hearing inter-channel differences... so it seems worthy to try moving up to a higher sampling rate from a delivery point of view.

What's the catch?  Well, you need a lot more storage, and you make the jitter problem worse.  Combined with the requirement to optimise a converters' characteristics for the higher rate, this means a converter may well sound better at a lower sampling rate.  An interesting test of this is to downsample high resolution audio... I developed a program called FinalCD to do just that.  It is a clunky, old-school command line program but is fairly well regarded in terms of its sound quality.

Certainly, I designed the sharp filter to capture as much as possible of the original 96kHz signal into the 44.1kHz sampling rate limitation of Compact Disc.  While it would be possible to go more precise still, it is really pushing close to the limit of what can be crammed on there and is technically close to perfect.  Many years ago, perhaps around 2004, I used FinalCD to compare a 24/96 recording to a 44.1 downconversion of the same material.  In the same player, the 44.1 sounded better... in a different player with completely different transport/DAC architecture?  Same result.  The 44.1 just sounded more musical.

This didn't make any sense at the time, but as mentioned above, this is not hugely surprising when everything is taken into account... running a D/A at a lower sampling rate increases the tolerance to jitter for reproducing the waveform correctly.  You are trading the ability to time the signal transitions correctly effectively against the settling time or amplitude precision of the D/A... this is precisely why delta-sigma converters suffer so much from jitter, as they need to run much faster to make up for their lack of raw resolution, often only composed of 31 or so elements... less than 5 bits.

In any case, time moves on.  Since developing the Discrete DAC many years ago and combining it with custom digital filters and dither running on my Ti48 equivalent, I've been fairly content with the quality of my CD playback, with no big steps for improvement... the limitation seemed to mainly fall on the source.  Now I am an advocate of the potential of 16/44.1 and feel that it has been hard done by for many years with some truly terrible recordings and masterings (perhaps done under duress in the latter case), but there was always the nagging feeling that a bit more bandwidth could help if done right...

Aside from the work done on Sunrise, improving my analogue replay massively over the past year has perhaps shown better where CD would ideally be than any high-res recording had done so to date... so it was time to do some more investigation into the possible reasons.  To do this, I'd need some more  "Hi-Res" material... ideally material I was familiar with and already had on multiple formats - it might help to shed some light...