High-resolution audio

I have been interested in high-resolution audio (hi-res) for many years. I bought my Apple MacBook in 2019. I thus do not have the M1 chip version. I have many Mp3 files and some FLAC files too. I wanted something that sounded substantially better than what my Mac was capable of. I thus began my quest to explore this topic. 

Getting started…

The sound we hear (rock and roll, people talking, birds chirping, etc.) is always in an analogue wave format. The very best sounding digital files thus accurately retain all the information provided in the recording process.

“Lossless” files refer to a type of compressed digital audio that uses advanced data compression algorithms to ensure there has been no loss in data – hence the name! The quality of the lossless file, therefore, depends on the original source that’s being compressed. Lossless files include ALAC, FLAC, WAV, DSD, AIFF, etc.

Lossy compression is a way of getting even smaller file sizes. The algorithm used in a lossy audio format compresses sound data in a way that discards some information. This process is irreversible and thus, permanently damaged. 

The encoded audio is NOT identical to the original and thus inferior in quality. MP3 is an example of Lossy compression. Lossy files are often used by streaming services as they…

  1. Save storage space
  2. Enable faster downloads

Identifying a high-resolution file

Many companies use the phrase “CD quality” to sell their digital files. However, “CD quality” is set at 16-bit/44.1kHz. Hi-res audio tends to refer to music files that have a higher sampling frequency than CD quality. So, normal CDs are NOT hi-res and thus, have average sound quality.

The Super Audio CD (SACD) sampling rate is 2822.4 kHz, and the resolution is one bit. The SACD is very high-resolution audio, and the sound quality is obviously superb. SACD is a true “Hi-res” CD.

MQA stands for Master Quality Authenticated, an audio technology making hi-res audio streaming a reality. MQA takes original high-resolution studio recordings and ‘folds’ (compresses) them through a multi-step process and stores them in either

  1. 41kHz or a
  2. 48 kHz container file.

Even though the second higher rate is above “CD-quality”, MQA uses lossy compression and is thus, NOT “Hi-res”.

At least one streaming service serves FLAC at 16bit / 44.1kHz which is “CD quality”. FLAC stands for Free Lossless Audio Codec. So, it must be good, right?

FLAC files can also go up to 24-bit/192khz and they would be much more “hi-res” – So, here we have an example of a lossless file being used to sell average quality music. This illustrates why it is important to check the sampling rate too.

Files can sometimes have a low resolution and then, they get transferred to a Lossless file format such as FLAC. The new version will NOT sound any better! So, it is worth trying to check the validity of the files you are downloading. Signing up for a good quality streaming service like Qobuz would take away this worry.

Let us examine the implications of file size. MP3 is a very low resolution at 256kbps and will get you a little under 2MB a minute. On the other extreme, Mari Kodama’s pure DSD-recorded Beethoven Piano Sonatas (16 and 18), is a stunningly beautiful recording at very hi-res. It is 2.7GB in size and you only get 9 tracks! To put this in further perspective, a 2.7GB hard drive can store well over 350 MP3 tracks. This illustrates the chasm of difference between a rather ropey low-res MP3 file and a stunningly high-resolution audio file containing every nuance.

Listening to high-resolution audio allows you to pick up on the subtle details and nuances that you would hear in a recording studio. So, if you’re waiting to get your hands on Adele’s album “30”, try listening to it in high-resolution audio. It’ll sound like you pulled up a stool next to the British diva, allowing you to hear every note of her soulful, impressive range.

What to look for?

Here are a series of important questions that help you find good digital music files.

  1. Does it mention…
    • Lossless
    • Hi-res
    • HD audio
    • WAV, AIFF, FLAC, DSD, PCM or ALAC
  2. Does it have a high sampling frequency rate?
  3. Is it honest?
    • “CD quality” and MQA files are neither masterful nor “Hi-res”.
    • Lossless files that have the “CD quality” sampling rate have probably been copied from lossy files. They won’t sound any better!

If all three answers are “Yes”, you probably have a winner.

The transmission of hi-res files

High-resolution lossless audio (over 48 kHz) isn’t supported via AirPlay as a protocol, regardless of Apple Music. Wireless streaming is thus good for listening to MP3 files on iTunes, but nothing hi-res. So, if you have a vast number of MP3 files and stream wirelessly, you won’t need an expensive hi-fi system anyway. 

Bluetooth is limited when it comes to streaming lossless hi-res audio. Bluetooth tech transmits audio wirelessly using lossy compression that discards data. Even the latest and greatest Bluetooth version, AptX Adaptive, a format that claims support for high-resolution audio, uses lossy compression. Beyond this key limitation, Apple products don’t always provide support for the more basic Bluetooth AptX version (I enabled it on my Mac), so high-resolution audio streamed from an iPad/Mac via Bluetooth is a non-starter. Bluetooth is also unreliable, but it is very convenient and if you are busy like me, it can make listening to music so much easier. 

To achieve the highest audio quality via USB, though, demands that the interface be operated in an optimum way. USB supports three different modes of data transmission – adaptive, synchronous and asynchronous – but only the last of these is compatible with state-of-the-art audio. First-generation USB-equipped DACs typically used one of the other modes and were often restricted to 16-bit resolution and 48kHz maximum sampling rate. As a result, they delivered poor sound quality.

So, if you want to get the most out of hi-res files, you will probably want to…

  • stream the files via fast, cabled and reliable broadband internet
  • use asynchronous USB between your computer and the Hifi equipment
  • find equipment that is designed to process hi-res files
  • use good cables to connect other devices directly to minimise losses in data

Disadvantages of uncompressed lossless audio

  • DSD is different in that its underlying audio storage is pulse-density modulation (PDM). This makes certain demands on your playback equipment for “true” PDM support, although other mechanisms exist to convert the DSD signal to PCM for broader DAC support.
  • There are far fewer bands/publishing labels that actually offer DSD recordings. DSD is NOT a mainstream format. FLAC usage is widespread.
  • Due to its high-quality codec, DSD is impractical for streaming. WAV and AIFF files are also impractical for streaming due to their file sizes and general availability
  • You would probably have to do things in a very specialised way to use DSD, WAV or AIFF files, e.g. subscribe to websites that offer these files (and they are expensive due to the storage space requirements, etc) and have a dedicated ethernet connection with fast reliable broadband internet, etc. This is not always the case with FLAC.
  • A low-resolution track upscaled to DSD, WAV or AIFF will not sound any better!
  • DSD is, thus, not always magically better than its rivals. A ‘standard’ DSD file – often referred to as DSD64 is roughly equivalent to a sample rate of 24/88.2kHz. ‘Double DSD’ or DSD128 samples that single bit of information 5.6 million times a second to give you a signal equivalent to 24/176.2kHz. Again, this is a sample rate that can be reproduced by formats that are not DSD. Higher rates exist but they are very, very rare and you really do have to hunt them down.
  • It’s not very practical to manipulate a DSD recording. Many things are required post-recording such as equalisation, editing, dynamic range control and adding reverb, etc This usually involves the DSD stream being converted to PCM to do the processing and then switched back. That’s hardly a pure way of doing things.
  • DSD files can have issues with background noise too. FLAC, WAV and AIFF files are often cleaner.
  • WAV, DSD and AIFF files are very large. To compare, a CD recording (44.1 kHz, 16-bit) is ~30 MB on average, while standard WAV can take up to 500 MB. Mari Kodama’s pure DSD-recorded Beethoven Piano Sonatas (16 and 18), a beautiful recording, is 2.7GB and you only get 9 tracks.
  • All digital files can get corrupted and/or be difficult to play. These issues can easily be overcome by changing the software used to play them and/or by downloading a better file. This is again easier to do with FLAC.
  • Metadata is not standardised in WAV therefore some metadata may be lost in the conversion to WAV.
  • Uncompressed audio formats can seriously affect every aspect of your setup. You will need to carefully consider the quality of Hifi components used, the quality of internet provided, the software required and whether or not it deserves a dedicated room with proper acoustics, etc.
  • For DSD, AIFF and WAV files, it makes sense to use specialist websites with reviews, subscribe to them, read thoroughly to find the best recordings and download them over an ethernet cable. This will be both time-consuming and ludicrously expensive. If you then compare the downloaded file with the FLAC of the same recording, you could actually disagree with the original recommendation. But, you will have lost both time and money finding that out.

Which file format is the best?

  • All lossless files have excellent sound quality. So much depends on what system you buy, what kind of music you like, how much money you are willing to spend and your personal preferences, etc. Some people will prefer a DSD recording of artist A and then prefer the AIFF for artist B, etc. System configuration can also affect the type of file that sounds best on it and the recording can have a massive impact too, etc. Finding which lossless file works best on your system will be a nightmare. It isn’t practical. Everyone simply gets what they can.
  • FLAC, AIFF and DSD files support the inclusion of metadata. So if you have a Hifi system with a screen for displaying it, you can learn a lot about the recording and/or have an aesthetically pleasing display (Album cover, artist, track title, length of the song, etc.) that encourages you to listen to more music. If you are streaming the music from Spotify, for example, you may also see the Spotify logo on your screen too.
  • If you are very rich, have time to spend finding the files and really want the very best sound, well-chosen DSD, AIFF and WAV files could give you the best sound available – if it really, really matters!
  • FLAC beats uncompressed lossless formats on file size by up to 60-70% at times. That is a truly massive saving and will have a massive knock-on effect in terms of storage space and everything else too.
  • You can easily get hold of FLAC files for free on torrenting websites such as 1377x This is not the case for DSD, WAV and AIFF. You will probably pay through the nose to get them, store them and play them.
  • Why would you waste time and spend, literally piles of money finding files, storing them and buying equipment to play AIFF, DSD or WAV files? Is it because you want to boast about how good your system is? Do you have a life outside of your music? FLAC files are also lossless. So, you could possibly miss out on a few tiny details – but, so what? How are you going to know anyway? Were you present at the recording?
  • Some people struggle to tell the difference between a FLAC and other lossless formats. That says a lot for FLAC 
  • FLAC files simply have very few issues and when they arise, they can usually be resolved easily. This is less likely with DSD.
  • DSD, WAV and AIFF files are not practical for most people. FLAC files are simply far more accessible. They are the clear winner.
  • I personally use FLAC files for the music I listen to the most and MP3 files for everything else stored on my computer and I use Spotify for listening to some rare hard to find albums. However, artists like Neil Young, Joni Mitchell, David Crosby, Stephen Stills and Nils Lofgren have boycotted the platform. So you may have to buy their music instead.

Narrowing down the list of attributes

I think it is preferable to have both wireless and a properly connected network solution. It thus makes sense to look for products that support Bluetooth Aptx, asynchronous USB and cabled ethernet. The real questions are…

  1. Do you travel a lot?
  2. How much money do you want to spend?
  3. How serious are you about Hi-res audio?

If you travel a lot, then it makes no sense to buy a fancy Hifi system. You are better off with a portable digital music player such as the Cowon Plenue D3 – a What Hi-Fi? Awards 2021 winner. It supports 24-bit/192kHz WAV, FLAC, ALAC and AIFF files and 64GB of built-in storage, which is expandable to 192GB with the addition of a 128GB microSD card. The PD3 boasts DSD128 file compatibility too – and that support is native, so DSD files aren’t converted to PCM during playback.

Another option would be to use an Ipad and buy some small speakers/headphones that connect to your computer via an AudioQuest DragonFly DAC. There are a large number of expensive solutions. I am not going to explore this route because money doesn’t grow on trees! Moreover, I think you can get a fantastic hi-fi system without breaking the bank.

If you are really serious about hi-res audio, you might consider ditching Itunes altogether and buying a dedicated music server and/or streamer, etc. If it is the server, you will need to acquire or transfer high-resolution audio files of your music to it and this can quickly become expensive when you need more storage units. The streaming solution would need a fast, good quality and very reliable ethernet. You may also need to pay for a subscription service such as Roon – so again, it can become expensive.

Let us start with the computer

We can easily install the “Bitperfect” application on an Apple Mac device with Itunes. BitPerfect is a simple, easy to use, audiophile-grade music player that works in conjunction with iTunes to deliver the highest possible sound quality. It is a free application available on the Apple store. More information on Bitperfect can be found here.

You can also buy a DSD master app from Apple too. DSD Master is a professional-grade tool for producing PCM versions of music files encoded in the DSD format. It produces BitPerfect Hybrid-DSD files required for playing native DSD using BitPerfect and iTunes. It produces the highest quality PCM transcodes on the market – better than those produced by professional studios.

You might want to consider creating a Plex account online for free. Plex is a free Itunes alternative. Neither of them is an optimal solution. You can also use a Mac Mini to create a server as detailed below. If you are unhappy with using your computer as a music server and want something better, you will probably be interested in products such as the Innuos Zen Mk3, Melco N100 or Aurender N30, etc. These products are expensive. I think the Innuos is probably the best choice as it comes with fantastic software.

All Bluetooth devices support the low-power SBC audio compression codec as standard. Fortunately, modern Macs also support AAC (Apple’s preferred iTunes codec) and aptX, which Android devices often use. These two codecs offer higher quality audio and generally lower latency than SBC, which is why most third-party wireless headphones on the market support one or the other, and sometimes both. I was able to enforce Bluetooth Aptx on my Mac. You can find plenty of information online detailing how to do this. Bluetooth Aptx does NOT offer a good quality high-resolution audio solution though.

If you are a bit more serious about high-resolution audio, you might consider subscribing to a music streaming service. Most, such as the market-leading Spotify and Apple Music, offer standard, lossy compression music streams, whether 256kbps or 320kbps, AAC, MP3 or Ogg Vorbis. Some, such as Tidal, Amazon Music HD, Qobuz and Deezer, also offer higher, CD-quality streams.

I quite like Spotify because it is free (but you do get adverts between tracks which is annoying. If you want it without adverts, you have to pay for the privilege). This is useful for accessing hard to find albums such as Marquee Moon by Television. Spotify will deliver music in CD-quality, lossless audio format to your device.

Roon is widely recognised as offering the best software solution and Qobuz has the best selection of hi-res files. Spotify is set to join the crop of hi-res streaming services with its Spotify HiFi tier.

It is worth remembering that an Apple Mac can process FLAC and some other hi-res audio files on its own. Dedicated devices such as a CXN (V2) are designed to do a better job.

Apple airplay does not support the playback of these high-resolution audio files and so, if you want to listen to them using a MAC/Apple device as a server, you will need a HiFi component that accepts the transfer of these files via asynchronous USB.

High-resolution audio equipment

In terms of an amplifier (which is at the heart of the Hifi system), the Cambridge Audio CXA81 has a USB B type socket fitted to enable the playback of audio directly from a personal computer running either Microsoft Windows or Apple OS. This USB input supports audio of up to 32-bit/384kHz and DSD256 quality, allowing you to make full use of its delightful presentation of high-resolution audio files, e.g. FLAC.

The CXA81 also houses a superior ESS Sabre ES9016K2M DAC and has an aptX HD Bluetooth receiver built-in for direct streaming from any compatible device at up to 24-bit/84kHz. The unit supports Google Chromecast, Spotify, Tidal, Qobuz, Roon and AirPlay 2.

So the CXA81 covers you for both wireless and cabled streaming, as well as wireless and cabled music listening from your music server (Mac or PC, etc). So you are getting a high level of functionality and good sounding high-resolution audio at an affordable price. Achieving a better sound; is probably going to cost a lot more money and the law of diminishing returns kicks in hard. Although, I must admit the Marantz Model 40n does look amazing. I myself bought the CXA81 as it is much cheaper than the Marantz – it has a button to easily select Bluetooth and this is handy for quick selection.

The Cambridge Audio CXN (V2) network streamer has been designed to work well with CXA81. It can process audio formats such as ALAC, WAV, FLAC, AIFF, DSD (64), WMA, MP3, AAC, HE AAC, AAC+, and OGG Vorbis. 

You can use a Mac Mini as a music server as detailed here. The cheapest method, probably, is to use a dedicated Network Attach Server (NAS) such as the Synology DiskStation which plugs straight into a CXN (V2) and will read the high-resolution audio files stored there.

Conclusion

The CXA81 amplifier is a good way to get started if you are interested in high-resolution audio playback using a computer as your music server. The amplifier is a What Hi-Fi? Awards 2021 winner which speaks volumes.

I recommend you read my post on streaming services or get an account with Qobuz to get the best high-resolution audio.