Integrating analogue with digital audio components is complex and not well explained, so I thought I would post the results of the extensive research I conducted while recuperating from an eye problem – which allowed me time to listen carfully to music. During my recovery I realized that the quality of our audio has degraded, it was better in the past using CDs.
Years ago we converted our audio CD collection to digital files hosted on a MAC mini using iTunes. This was streamed via ethernet (wired) to Apple Airport Express (Airplay), then to a Denon 4308 AV Receiver and then to 26 year old high quality speakers (B&W 802-80). This resulted in less than acceptable audiophile results. Thats the problem I am trying to address – the sound quality is poor using these components.
Interestingly, I am quite satisfied with the audio and video quality from a Blue Ray video disk or 1080p Video downloaded from iTunes store using the above equipment with HDMI cables. Where did I go wrong with audio?
This post serves two purposes:
- To explain the basics of digital audio such as codecs (FLAC, ALAC …) and provide a reference as I forget these things over time
- To document the solutions to problems so others can benefit from them and I don’t repeat the same mistakes
We have chosen to use the Apple echo-system but most of this post is generic and will work with other operating systems. Apple has provided us with the best user experience overall. Warts and all, it’s the easies way for our household to go (although we keep our options open).
I think its important that everyone in the household be able to buy and listen to music, including ease of use like turning the system on/off. I therefore have attempted to reduce the complexity of operating the entire system.
A few brief definitions for those new to digital audio:
DAC – Digital to Audio Converter – converting the digital streams of numbers to analogue sound
16/44 – a digital short hand for defining two key aspects of encoding sound. Refer to the sound wave diagram below:
– the first number (16) is used to define the number of bits for loudness (dynamic range from soft to loud). The greater the bit rate, the greater the difference between soft and loud and the larger the file.
– the second number (44) used to define the number of samples taken per second(in thousands). The more samples the better the fidelity to the original sound and the larger the file.
– Digital files are stored either Lostless (no loss of sound quality) or Lossy (sounds removed to save space with a potential audible loss in quality).
– The encoding of sound is arranged using standards called codecs. Most codecs don’t support tags such as Album Art and Track Names therefore the tags are placed into Files along with the codecs (the encoded music). The files are standardized and a few common file formats are .mp3 (which is lossy so its poorer quality) or ALAC which is lostless (high quality).
DSD is an entirely new encoding scheme, has little music available and requires a specialized DAC. I have decided not to go that route.
Overall User Requirements:
Playing music involves more than just using technology; its about ease of purchase, operating convenience, reliability and above all enjoyment. With that in mind I developed an overall set of requirements that balances those basic needs. I encourage everyone to consider their overall requirements, not just a few technical pieces:
- Purchase: how will you obtain the music, in what quality level and how will you place it into your music library
- Player: (Software such as JRivers or iTunes – I actually settled on Audirvana V2 and dropped the iTunes Library entirely)
- Remote: to select the music and turn on/off hardware and change the volume
- Quality: what bit depth and sample rate (24/192 – described in the tables at the end of this post)
- File Formats – ALAC, FLAC, AAC – (described in the tables at the end of this post)
- Connections between components to support the desired quality levels (example Toslilnk has limits)
- Streaming music from internet or hand held device (iPad …)
- Locations: where will the hardware reside, how will you connect to it (network and remote) and will it make too much noise, is there good clean power?
- Maintenance – do I know how to maintain the OS and Applications?
- Upgradability: I kept the components as separate devices (exception: integrated receiver) so that they could be separately upgraded as required
- Portability: Support iPods, iPhone music with down sample of audio files suitable for these devices
- Hardware to support all of the above
- Network Connections to support the above
- Overall Cost of Ownership: Recycle old Macs, use free software and put money where it counts: speakers, amp and keep other costs lower (cables and DAC)
Basic Technical Requirements:
- Player: iTunes – it’s the devil we know so the rest of the system has to work with it. (JRiver media centre would be a consideration – that will be another post some day).
- Purchase: The iTunes store does not have great quality levels, alternative stores will need to be sourced. Moving the music from the store to the “digital music library” needs to be document
- Remote: Use iOS devices as the “Remote app” to select music and replace all “other remotes” for power on and volume control etc. One remote to rule them all. On iOS I also installed Rommie which translates all other remotes from IR (infra red) to WIFI and back to IR for each component. I can therefore change the music, volume or power from any room in the house
- Quality: Support a stream rate of 24/192 (24 bit depth, 192 khz sample rate which is better defined at the end of the blog) when connected to a digital library hosted on a Mac computer. It is arguable that 24/192 is overkill for audio but at least this requirement should provide “state of the art” for a good while (maybe 5 years or so). Do you need DSD, if so then you will have limited choices for a DAC.
- Streaming: Support Airplay at its maximum throughput (which actually seems low at 16/44) to support some ad-hoc streaming from iOS
- File Format: I have decided to use ALAC codec (Apple Lostless) using the .m4a file format (non DRM apple file format). All of this is explained below as well
- Connections: For the majority of audio transfer use USB from the computer to the DAC since it supports the best quality audio with least distorition
- Location: Maintain a Music Library on a Mac in the listening area (Living Room) using a quiet older Mac Book Pro (2011) and quiet small external hard disk (1 – 2 TB), keyboard and screen. Since audio streaming is not CPU intensive any relatively modern PC will do. I will stick with a Mac since I already maintain several.
- Maintenance – I don’t want to learn how to maintain and operate many systems, I will stick with Mac and iTunes (although iTunes is still unreliable and not user friendly)
- Upgradability: Keep the DAC as a separate unit so that it may be upgraded over time. The remaining audio components are already high end and won’t evolve over time
- Software: Mac OS X, iTunes, iOS Remote, Roomie, XLD
- Limitations: What I will not pursue now: DSD file format – not enough music available at a reasonable cost and keep costs reasonable for the DAC since they are still evolving
Current configuration and the problems to solve:
Interestingly, I am quite satisfied with the audio and video quality from a Blue Ray video disk or 1080p Video downloaded from iTunes store using the above equipment with HDMI cables. Where did the audio go wrong.
|Computer -Mac Mini||As a file server it has been reliable for backups and hosting digital music files. Its external Hard Disk was noisy so I moved it to the basement and because the mini is “headless” (has no monitor / keyboard) it was hard to manage when iTunes had a problem (at least once every three weeks although its getting better over time).||Headless – some pain for me and very difficult for my spouse to manage. Otherwise use a monitor and keyboard and it works fine. I tried a NAS and found the graphical interface too primitive|
|Storage – External Raid 5 Hard Disk||Hosted the music files – noisy fan and disks. It also powered off the hard drives when not in use, requiring time to power them back on when selecting music||Noise – High, unusable in the living room and slow to start up (5-10 seconds)|
|Remote Control – IOS “Remote” App to change music||Works well but has a somewhat limited interface and Apple keeps changing the GUI making it harder to use||Works Fine – perhaps somewhat limited in its display of music selections|
|Airplay -Apple Airport Express via Toslink||Airport Express and Apple TV are currently limited by Apple to to 16/44 (16 bit, 44.1 Kbps which is CD quality). Toslink may introduce jitter – Airport express only supports Toslink therefore it can’t do better than CD quality.||Airplay – as far as I can determine, converts all incoming audio to 16/44 and then encodes it as Apple Lostless. Apple TV: re-samples it to 48kHz for playback. Toslink is limited as well to 19/44 so neither of these products can do much better than CD quality.|
|Music Player – iTunes||Not really designed as unattended Server based technology, iTunes really seems to require client input by a user with access to the screen. Annoying pop ups such as “enter password” messages would lock out any remote access via Remote App.||Least reliable component by far and the most painful- weird interface, confusing Store vs Library interface IMO|
|Amp: Denon 4308 AV Receiver||Good Home Theatre but not a high quality audio system especially for multi zone (in my case zone 2 – Living Room). Also functioned as the DAC.||Pain – lesser quality audio|
|File Format: ACC files at 320 kbps||Was ok at the time, but unfortunately is too low a quality level for high quality audio and its compressed(lossy). This means I have to re-rip most of my library of 500 CDs.||Pain – really high, what a drag to re-rip|
|Power Remote: iOS App Roomie||For a while we were using several remotes, turn off / on Denon, adjust volume, select music with Remote. Eventually switched to Roomie with reasonably good results.||Like many iOS apps, Roomie seems to be immature, although it is improving over time|
|Network Connectivity – wired ethernet||I prefer to stream music using wired ethernet to avoid WIFI congestion. Although I have set up a WIFI network that is quite robust. I prefer music to stay off the Wifi network and I appreciate that I don’t have any drop-outs on the music system. I prefer WIFI for products such as an iPad and by not streaming music wirelessly the bandwidth is available for those products that require it (iPad).||Its the most reliable way to go, served us well and I will stick to that.|
Solutions to the above problems:
|Computer: Mac Book Pro (2011)||Use a machine with a screen/keyboard to manage music, address iTunes glitches and the external USB hard disk is quiet. Keep in mind that the entire household needs to be able to listen to music and fix glitches so a headless server may be problematic||Sits quietly in the Living Room and causes few problems|
|Storage: USB 2 Hard Disk – Music Library||Ultra Quiet and small (USB WD Passport)||Sits quietly in the Living Room and causes few problems. Cheap and can be upgraded as required, backup to Mac Mini Server|
|DAC: Naim V1||Connect to the Mac (could be any Mac) via USB. Support 24,384 quality and as a separate component allows for future upgradabilityConnect to the Amp via RCA cables.||Using a separate DAC allows me to upgrade it at some time in the futureUSB avoids jitter problems with Toslink connections. I have heard this jitter on several occasions although its hard to determine if it is also because some of this music is compressed.|
|Speakers: B&W 802 Diamond Speakers||Outstanding audio quality||my last 802’s lasted almost 30 years, I see no reason for these to be any different|
|Amplifier: Naim SuperNait 2 Integrated||Ensures high equality audio capable of driving the B&W speakers|
|Naim NACA5 speaker cables||On my wish list – cables are important with high quality speakers as well as the connections.|
|Power Conditioner: APC G50NETB2||Surge Protection, Noise Removal and powers down Naim Amp which sleeps at 37w||Naim needs to do much better at green technology|
|File Format – ALAC||iTunes natively supports ALAC (lostless codec) and AIFF. AIFF files are about twice as big, since both are lossless, I will use the smaller files (ALAC). Philaudio is a lossless decoder and is available from the Mac store to convert ACC/FLAC to other lossless formats such as ALAC. For the few download sites that only provide FLAC, I will convert the files to ALAC.|
|Music Ripping – XLD Mac version (free)||iTunes can rip a CD to ALAC, however Philaudio seems to do better and it handles multiple drives. I found I could handle two high speed CD readers, while editing tags and correcting metadata issues.|
|Client Player – Audirvana||I am still not a great fan of iTunes and after testing most of the products such as JRiver I settled on Audirvana because of its better sound quality.
I also considered:JRiver Media Center – can’t really see how it helps me (v 19). Bitperfect – for $10 seems like good value – plays FLAC, PureMusic2 – looking into it.Dropping iTunes was difficult, although I have tried to remove all DRM (.m4p) tracks to ease problem with endless “enter password” requests.
|Regrettably iTunes does not provide a great ease of use nor has it been reliable.|
|AirPort – streaming||Having the ability to quickly stream audio to the stereo system seems convenient even though its limited to 16/44
I now stream from a iPad to a small number of Airport devices.
|I will therefore move the old Airport Express and connect it to the DAC via a Toslink. Its limited to CD quality and I can live with that for adhoc streaming|
|One “Remote” device to control the system||I never got around to setting up rookie, we use a MAC remote to mute and change volume to Audirvana.||I hope I can can configure Roomie to learn about the Naim amp with not too many issues. I also plan to program it to turn on the power to the system using the APC power conditioner via IP.|
|iTunes – Maintain support for iOS players (iPad, iPhone …)||iTunes is convenient to transfer the music library to and iPod for the car and cottage.One thing we will get rid of are the .M4P files which are DRM (Digital rights managed) as they cause nothing but problems since Apple has screwed up so many times with the Apple ID management. This is a hastle I will need to consider more fully.||So far, the Apple echo system as served us quite well – we will just stick with it – with the exception of .m4p files which we will delete|
|Network Connectivity – wired ethernet||Really there is not any network activity since the music library is locally attached to the computer. On those few occasions with Airplay streaming it would be wired ethernet to an Airport Express.||The airport express also runs a dedicated wifi for audio streaming to a B&W Zeppelin in the bathroom|
A FEW RANDOM THOUGHTS AND FACTS:
It should be noted that its generally agreed that in blind tests, people can not reliably differentiate the quality differences beyond 16/48 however there seems to be a better satisfaction with the musical quality at the higher levels. Its debatable.
|Sample Rate kHz||Bits||kbps
(kilo bits per second)
|44.1||16||1,411||96 db||Standard CD|
Codecs – Common Audio
Codecs are the sound recording formats used to interpret the sound. Some are lossless yet use lostless compression to save file space, without a loss of sound quality.
|Codec Audio||Lossless||Adopted by||Comments|
|AAC||No – Lossy||Apple||Most common iTunes format, lossy but more efficient that MP3|
|ALAC||Lossless||Apple||Not Error Robust||Supported by iTunes|
|FLAC||Lossless||Windows||Error Robust||Not directly supported by iTunes – requires a plugin|
Each file is a container (or wrapper) that the computer operating system manages. Some file formats support imbedded meta data (such as album cover image, track name) while others do not.
As of 2014 Apple sells music at 256-kbps in a compressed (lossy) format using ACC codec and .m4a file format. This is less than CD quality. This compression can be heard to the discerning ear on high end equipment. Most high resolution audio is sold using FLAC format which Apple does not natively support in iTunes, although there are third party iTunes addins that do support FLAC.
|File Format||iTunes Support||Embedded Metadata||Playable by iPod, Apple TV, Airport Express||Comments|
|.FLAC||No||No||Not Supported by Apple TV and Airport Express. May have iTunes support from 3rd party products|
|.M4A||Yes||?||Yes – most common||AAC or ALAC Codecs|
|.M4P||Yes||?||Yes||DRM and AAC|
|.wav||no||DRM or any Lossy codecs|
PLAYING HIGH RESOLUTION on any MAC
In order to hear the best sound quality on a Mac, the following must be performed:
- Open Utilities Folder: Finder > Shift+Command+U
- Select Audio Midi Setup
- Change Built in Output to:Format:96000 2-ch 24 Bit
- Connect the computer to the DAC using ONE of the following in preferred order: USB (24/192), Toslink(16/96), Airplay via ethernet (16/44), Airplay via Wifi (16/44) if no dropouts.
Lower res files will be up sampled to that rate, higher res files will be down sampled.
Ripping without iTunes
XLD is a lossless decoder and is available free which converts FLAC to other lossless formats such as ALAC.
Since I have to re-rip my entire library, I want to keep track the space required for higher quality files. Current iTunes Size – Prior to Upgrades Aug 2014:
78 Gig with about 10,000 tracks. On Oct 26, 2014 I completed the transfer of 540 albums (8332 tracks) using 171 gig ALAC format.
iPods don’t play 24/96 but iTunes will down sample automatically to an iPod. iTunes music is sold at 256-kbps and are AAC file formats. A CD is 1411 kbps (16 bits recorded per sample and 44,100 samples taken per second – 44.1kHz
We don’t subscribe to iTunes Match (we live off-line much of the time) and since many of our tracks were purchased with a different Apple ID, we are unable to upgrade the ACC files from 128 kbps to 256. Apple should fix this.