This is the start of a new series of posts about getting great sound from streaming audio services.
This post will focus on Apple Music played from a Macbook laptop to external speakers, not headphones. It would be equally applicable for other streaming services like Spotify, Rhapsody, and Pandora.
With the advent of streaming services with tens of millions of tracks, I’ve decided to figure out how to build a nice sound system with these as the source material. This series of posts will focus only on streaming services and not delve into other sources like CDs, digitised music on disks and other digital sources. There are thousands of articles already on these sources covered by magazines like WhatHifi, Stereophile, The Absolute Sound and the like. I’m more interested in being liberated from having to listen to a private library of content so services like Spotify and Apple Music are my focus where for about $10 a month, you can access tens of millions of tracks.
Any modern Mac can playback audio. You can listen to music via the laptop’s built-in speakers or via headphones. But what’s the best way to get playback via a set of external speakers? Before we get to the answer, the very important role of the Digital to Audio Converter – DAC – needs to be explained.
The DAC is the bit of magic hardware and software that converts a music file into sound. Whether the music file is store on your computer or streamed through the Internet, a DAC is needed to convert that into sound. The Macbook computer has a DAC, so when you play music on your Mac and listen through its speakers, the Mac’s DAC is being used to convert the digital file into analogue audio. Similarly, if you plugged in a set of headphones, the Mac’s DAC is used to convert the file into sound.
There are three ways to get an audio feed from the Mac to an amplifier. One is analogue and two are digital. The analogue method is via a cable plugged into the headphone jack connected to your amplifier. This will give you the lowest quality because the sound is emanating from the Mac’s DAC which isn’t designed for high-quality sound playback. The two digital methods are via the Mac’s USB port and the optical audio port. These methods bypass the Mac’s DAC and require the use of an external DAC. Note, the Macbook Air doesn’t have an optical audio port.
There are dozens of DACs that are standalone units. There are also amplifiers that have built-in DACs (e.g. NAD D3020). If your amplifier doesn’t have a built-in DAC then you’ll have to get one to sit between your Macbook and amplifier. Stereophile magazine has a list with DACs starting at $149, and here’s the WhatHifi list and Darko’s list. Most of these DACs can connect to the Macbook via the optical audio port via a cable known as a TOSLink, or the USB port. The USB port is generally accepted as the preferred method.
What the audio world is now discovering is that while digital signals are just 1s and 0s, it’s very important to get this data stream to the DAC in a manner that doesn’t introduce what I call digital noise. This noise is known as jitter. Here’s a good explanation: Jitter Does it Matter. To reduce jitter, it’s important to have a DAC that has such reduction circuitry, or use a device like the Wyred4Sound Remedy which reduces jitter on the TOSLink and devices like the Wyred4Sound µLink and the Audioquest Jitterbug that does a similar job if you’re using USB to transmit the digital signal to the DAC. There’s an article on the Remedy here. There are also devices that convert USB to SPDIF in order to provide a cleaner signal to the DAC. Here’s the list. The more expensive DACs like the Auralic Vega tends to have more sophisticated circuitry reducing the need to have these in-line jitter reduction devices.
So, now that you have a clean digital signal going into the external DAC, the output will be the best analogue signal the DAC can give you to connect into your amplifier.
The quality of the connecting cables between your Mac, DAC and Amplifier also makes a difference. There are lots of reviews, here’s a useful list to get you started.