What a music streamer does, and whether you need one

What happens between the app and the DAC

A streamer is a small computer with one job. You pick music in an app on your phone or tablet, and the streamer fetches it, from a service such as Tidal or Qobuz over the internet or from a NAS or a computer on your home network. It decodes the file, which from those services usually arrives as FLAC, into a plain stream of samples, keeps some of it in a buffer against gaps in the network, and sends it on at the file's own sample rate, either to a DAC in the same box or out of a digital socket to yours.

None of those steps changes the music data unless something along the way alters the samples. The conversion to an analog signal happens in the DAC, which the DAC page covers.

Streamers, streaming DACs and all-in-ones

Three kinds of box carry the name.

• A streamer on its own, sometimes called a network transport, has only digital outputs, such as USB, coaxial, optical or AES/EBU, and feeds a DAC you already own. A USB DAC that follows the USB Audio Class 2.0 definition can play through it without a driver from the DAC's maker.
• A streaming DAC puts the converter in the same box.
• An all-in-one adds an amplifier. The HIFIMAN EF499 puts a streamer for Tidal, Qobuz and a NAS in a $299 box with an R2R DAC and a balanced headphone amp. It has no analog input, so everything it plays goes through its own converter.

Built-in streaming can widen what a unit accepts. The HIFIMAN Serenade takes up to 32-bit/768 kHz and DSD512 over the network, against 32-bit/384 kHz and DSD256 over USB.

A DDC is a different box again. It takes USB from a computer and passes the data to a DAC timed by its own clock, and it fetches nothing from a network. The jitter page explains what that changes.

How a streamer finds your music

Files stored at home usually reach a streamer over UPnP, often labeled DLNA. Server software on a NAS or a computer shares the library, the streamer acts as the renderer, and a control app browses the server and tells the renderer what to play.

Streaming services have their own routes. Spotify Connect, Tidal Connect and Qobuz Connect work from the service's own app, which tells the streamer what to play; the streamer then pulls the music straight from the service. The phone is only a remote, so a call or a flat battery doesn't stop the music.

AirPlay works the other way round and sends the audio from an Apple device to the receiver, while Google Cast hands the stream over much as the Connect protocols do. Both have format limits of their own. Which of these a streamer supports decides what you can play on it, so check the list against the services you use before you buy.

How Roon works, and what Roon Ready means

Roon is music software built around a server, which Roon calls the core. The core runs on a computer, a NAS or a dedicated box, holds your library and merges it with Tidal and Qobuz, so they browse as one collection. Apps on phones, tablets and computers control it, and the core sends audio to endpoints around the house.

Roon Ready is a certification for those endpoints. A streamer or DAC that carries it receives audio over Roon's own network protocol, RAAT, and has been tested by Roon Labs. Roon can also play to AirPlay and Chromecast devices.

Processing happens on the core before the audio leaves. Roon's DSP can apply EQ, sample-rate conversion, crossfeed and room-correction filters, and its signal path view shows every stage between the file and the endpoint, marking whether the stream stays bit-perfect. Roon needs a paid subscription, and the core has to be running whenever you listen.

Does a streamer sound better than a computer?

Played bit-perfect, a streamer and a computer hand the DAC the same numbers. Bit-perfect means nothing between the file and the DAC changes a sample: no resampling to a fixed system rate, no volume set in software, no mixing with alert sounds. A computer's operating system can do all three unless the player takes exclusive control of the DAC.

What can differ is electrical. A computer's switching supply and busy circuits can put noise on its USB connection and ground, and whether any of it reaches the DAC's output depends on how well the DAC isolates its input. A streamer is a computer too, so the result depends on how each box is built and powered, and the same swap can be obvious on one system and inaudible on another. The rest of a streamer's case is practical: no computer to keep running or to interrupt playback with updates, and control from your phone.

Whether a hi-res file holds anything a CD couldn't is a separate question. The hi-res audio checker shows what a file contains above CD bandwidth.

Wi-Fi, Ethernet and network upgrades

A CD-quality stream runs at about 1.4 Mbit/s before compression and a 24-bit/192 kHz one at about 9.2 Mbit/s, and FLAC shrinks both. Ordinary home Wi-Fi carries that comfortably, and the buffer absorbs short drops in signal. Ethernet removes the radio link altogether, which makes it the steadier choice far from the router or among many neighboring networks. The EF499 and the Serenade both stream over an Ethernet jack.

On a network, data that arrives damaged is discarded and sent again, so a cable or a router can't change the numbers the DAC receives. What gets argued about is electrical noise riding on the network into the streamer. The standard requires Ethernet ports to be electrically isolated, usually with small transformers, though a shielded cable can still join two chassis through its shield.

The reviews here are listening reports, and they differ. The Synergistic Research Network Router UEF, a wired-only router from $2,995, gave everything its reviewer streamed a darker background and narrowed the gap between Tidal and local files. Its review lists as a con that nothing it changes shows up on a frequency response chart. To guard against placebo the reviewer matched levels and swapped the routers many times, and is certain the difference is there, while declining to call that listening proof. The one OFC CAT 8 cable in our Monosaudio cables review ran from a network switch to a music server, and its reviewer found the change barely noticeable, if at all. The best headphone amplifiers guide ranks the streaming DAC and amp units reviewed here, the EF499 and the Serenade among them.