Digital Music

My Digital Streaming Choices

The following diagram depicts the various components I have implemented in my digital playback system.
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The NAS Drive is used to store all my music files primarily because it offered a facility called "Raid Mirroring".
  • This requires two hard drives and maintains a copy of each file on each drive
  • in the event of a hard drive failure you simply replace the defective drive and the NAS unit populates the new drive with the content from the other drive automatically
  • It is recommended that when implementing RAID, you to use high quality drives such as those used in servers, in order to minimize disk failures. Normal hard drives are not robust enough for this kind of use.
The Ethernet Router provides a "hard wired" link from the NAS drive to my iMac
  • I chose this method over a wireless link for reliability.
  • In my neighbourhood there are a lot of wireless routers that seemed to cause dropouts during playback of the larger hi-res files.
  • It is also the fastest method of transferring data between computers.
The DSL Internet Modem provides my link to the internet and provides wireless capability for other ancillary computing devices such as tablets and smart phones
  • I use both my tablet and smartphone to control playback of digital content via my iMac
  • I use an Android App called Retune, which interfaces very nicely with iTunes that is running on my iMac
  • My Windows computers can also access and play content stored on the NAS drive by using iTunes for Windows
The iMac is the computer I use to stream digital content via it's USB interface into the DAC via the V-Link192.
  • There was a time when USB was considered to be a poor choice for streaming digital content to a DAC, primarily because the USB interface was not really designed for music, unlike other digital interfaces such as S/PDIF and Toslink interfaces.
  • There were issues that caused jitter, which resulted in poor sound quality
  • The introduction of Asynchronous USB has remedied many of the issues, together with better USB interface circuitry that is present in most current DAC designs.
USB Related Issues.
  • The USB circuitry in my V-link192 USB/SPDIF converter utilizes the power provided via the USB cable. As a result of this design, there can still be noise pollution created in the USB cable itself.
  • Therefore, I have chosen to use a Double USB Cable that consists of two separate cables that are joined only at the USB plug that connects to the V-Link192.
  • One cable transfers only the digital signal and the second only provides the USB power.
  • The power provided via the computer's USB port can also be noisy, so to remedy that I have chosen to use a separate USB power adapter in order to provide a very stable and noise free 5 volt supply to the V-Link192
  • This ensures that the V-Link192 is getting the cleanest digital stream possible and the cleanest most stable USB power.
The Musical Fidelity V-Link192 USB to S/PDIF converter
  • This is purpose built to handle USB issues related to timing and jitter
  • It is significantly better than the USB port in the Schiit Bifrost DAC and many other DAC’s for that matter
  • It provides significantly better sound quality, but only if the quality of the S/PDIF cable is capable of hi-res transfers also - many are not.

DAC/Computer Compatibility Issues.
Ensure you know the maximum sample rate for each input/output (i.e. USB, toslink and S/PDIF) - on both your DAC and Computer
  • e.g. on a computer, the USB sample rate may be 24/192, but the S/PDIF sample rate may only be 24/96
  • likewise, on a DAC the sample rate for USB port may be 24/96 and the S/PDIF is 24/192
  • Net result of this combination is a maximum sample rate of only 24/96
  • Be Aware: some brands of DAC and computer only advertise the upper limit - e.g. 24/192.
  • So download the manual before you buy if there is not enough information available on hand to determine the max resolution for each interface.
So that is my digital rig explained in a nutshell - what else is there to know?

To start with there are issues that many people might not be aware of pertaining to the copying of digital content from a CD.
  • When copying, some "Ripping Software" does not actually copy all of the raw data, but compresses it in an attempt to save space.
  • Unfortunately this fact is not always apparent and generally goes unnoticed.
  • I found this out the hard way and now use a program called dbPoweramp to copy the raw format from my CD's
  • The improvements in sound quality are quite noticeable.
Then there are issues with the type of digital file you elect to use for storing music, such as WAV, AIF, FLAC, ALAC, MP3 etc...
  • The best method of storage would be to use the format that is on the CD, but WAV presents a problem if you are using iTunes, because iTunes does not really handle the WAV metadata very well.
  • The net result is that if iTunes ever corrupts it's internal database then it is unable to rebuild the library from the metadata associated with every WAV track
  • You have to reload every CD in order to rebuild your library if you do not keep it backed up on a regular basis
  • Because of that I use AIF, which is Apple's version of a WAV file and is not compressed
    • and in the event of some iTunes “anomaly”, it is able to rebuild the library from metadata on each AIF music file
  • Some formats are slightly compressed and other like MP3 are very compressed - it really does affect sound quality!
Then there are issues pertaining to the programs used for playing digital files, where the program you use to control playback may alter the digital content before sending it onto the DAC - e.g. up-sampling, digital volume and Tone Controls
  • Up-sampling is where the playback program will insert "interpolated data" into the digital stream before passing it onto the DAC.
  • Interpolation is an approximation between two known data points and those that use it believes it enhances the sound.
  • Fact is, it can actually degrade the sound quality in many cases.
  • To ensure that this does not happen I use a program call Audirvana, which bypasses all internal Apple programming and passes only the raw data from the file to the DAC
  • The Bifrost DAC also processes at the sample rate imbedded into the digital file
    • many DAC’s simply Up-sample without you knowing.
  • volume and tone controls, although handy, can degrade sound quality considerably

Think That’s It?

Not Quite - there is one last thing to consider.

The designers of early DAC technology believed up-sampling within the DAC was a good idea.

However, as with all things in this hobby, things change and the latest approach is to allow the DAC to process the file in it's "native resolution".
  • Many believe for the "purest" level of playback you should be looking for a DAC that does not up-sample
  • often referred to as a non-oversampling DAC or “NOS DAC”
  • I have owned both types of DAC abad both are very good performers
  • But the NOS DAC seems to offer the best sound quality with crisper micro dynamics and imaging
So What do I mean by resolution?

The resolution of a digital file depends on it's bit depth and sample rate...
  • bit depth - is the number of bits used to represent "a sample"
  • Sample Rate - is the frequency at which samples are taken
  • Together they define the resolution of a digital file - e.g. CD's are generally 16 bit at 44.1 kHz or commonly referred to as 16/44
  • Other sample rates include 24/44, 24/48, 24/96, 24/176, 24/192 etc...
  • The higher the resolution the larger the file and the longer the download!
  • if you increase the sample rate you should be able to recreate a more realistic analogue signal
  • Up-sampling is the process whereby a 16/44 digital file is converted to a 24/96 file by filling in the missing samples with approximations calculated by the process of interpolation - it's an educated guess, but it affects the sound
  • For more information you should really refer to Wikipedia

What about ...

Streaming internet radio is accomplished via my iMac using iTunes - it's pretty simple

Spotify and similar music services - I do not currently have any experience with - yet Happy
Downloading hi-res music files from the web can present issues, e.g. iTunes does not play FLAC files
  • Audirvana does play FLAC files, but not easily in my implementation, so I simply convert FLAC to AIF
  • DSD in my implementation is handled automatically in real time at playback by Audirvana, so I have no need for a DSD compatible DAC
That's about it
Needless to say, this is but one example of a digital music reproduction architecture. There are limitless other possibilities, each with their own foibles to be overcome.
At least you now know of some of the pitfalls
Happy

UPDATE: I’ve since removed the DAC and V-link192 and replaced it with the Blusound NODE 2, connected via an ethernet cable to the NAS drive.

This eliminated the need for USB cables and computer software updates - a much simpler approach with better sound quality

Overcoming USB Streaming Issues

There’s a lot of discussion on the web about why the USB interface is not suitable for streaming music.

Much of the discussion promotes solutions that require the use of additional components that strip the music related data from the data stream, reassembles it with new clocking data and presents a squeaky clean version to the DAC.

Some even converts the data stream to a format supported by either the S/PDIF or Toslink interface.

The bottom line is, that you end up spending lots of money on a new component, related power cables/adapters and the various interconnects required, when in fact your own personal listening requirements may be satisfied with a less complicated solution

So let’s look at some of the issues...

Three issues I consider the most serious with respect to the degradation of the digital stream when using the USB interface are...
  1. EMI between the power and signal conductors inside the USB Cable - i.e. noise in the data stream resulting in jitter and noise in the power conductors effecting DAC performance.
  2. the unstable and noisy USB power supply - can effect DAC Performance
  3. the quality of the USB interface in the DAC you are using - unable to handle noise in the data stream effectively

Addressing #3 is not covered here since it is manufacturer specific and dependent on the DAC you are using.


Issue #2 may also related to the DAC you are using because some DAC’s utilize the USB power supply to power their own internal USB circuitry. Those that use their own internal power supply are much better equipped to handle a USB Data Stream.

Issue #1 boils down to the USB cable you select - not all cables are equal!
  • The most effective solution is to separate the data and the power conductors by using a cable like the one below...

The Power supply and USB with cable separate audio signal cable from Doukmall on eBay
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Now, you can still insert both USB cables into the computer, but for the best solution a separate power supply should be used.

Once again there are a myriad of solutions out there, but after trying several different power adapters I have opted to use...

The ENERCELL AC to USB Power Adapter 5VDC 1000mA 2730414
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I have found that using this adapter is as effective as using a battery power supply, which is perhaps the most stable 5 volts you can get.

Now, this IS NOT the be-all and end-all of solutions for USB interface issues, but for those of you looking for a cost effective solution that will address many of the most severe problems without adding even more components and cables to your rig and more importantly, without breaking your bank - then give it a try.

I hope you found this useful Happy