What’s Really Going on in Your Audio Stream?

Software, hardware, and operating systems silently modify the audio stream without providing any feedback all too often. Roon is changing that with Signal Path.

When we set out to create Roon, we felt very strongly that our customers should have access to honest and precise information describing how their software and hardware devices are performing audio playback. It’s very easy for poor system design, or poorly implemented or mis-placed DSP to ruin an otherwise excellent experience. That experience degrades further when your audio components modify the audio stream without any feedback.

If you’re not already a Roon member, be sure to sign up for the free trial so you can follow along in this article:

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What is Signal Path?

Signal Path shows you exactly what is happening in your audio stream at any given moment, and is always just one click away.

It tells you what your source material is, your output, and every detail in between. Whether it be bit depth or sample rate conversions, parametric EQ, other DSP options, or processing inside of your Roon Ready device, Signal Path lets you know.

Device Branding

We also feel that great audio hardware should be showcased. As such, whenever Roon is playing to a Roon Ready device or a recognizable Roon Tested device, we include branding, artwork, and product manual links. Our ability to support specific hardware devices is deeply related to whether or not we can lay hands on it during development, QA, and when addressing support incidents.

If you don’t see your favorite hardware manufacturer in our Partners Matrix, please get in touch with them. There are no costs associated with our programs other than the requirement that hardware samples be made available to us.

Working closely with device manufacturers

One of the primary goals of Signal Path is to work closely with device manufacturers to ensure that any processing happening in their devices is also accounted for.

Many Roon Ready devices are simply DACs or bridges with not much going on inside of them, thus they don’t reflect anything extra in Signal Path. That said, some devices do have additional internal processing, and as part of our certification program we require that it be portrayed accurately.

This level of coordination between software and hardware platforms is unparalleled, which is why Signal Path is such an exciting part of Roon, and why it’s unique compared to similar features in other software applications.

Take for example the Bluesound PULSE 2, a premium Roon Ready streaming player. Signal Path (pictured below) shows that Roon is sending a 96kHz 24bit stereo file to the PULSE 2 losslessly via RAAT. When the PULSE 2 receives the signal, it passes through its internal amplifier which does audio crossover and EQ.

This is custom DSP inside the PULSE 2 that Bluesound have developed — it’s a defining characteristic of the device that improves driver performance and contributes to its exceptional musicality:

We’re continuing to advocate for integrity in the audio stream, and you can check out the partners who have also joined us on our partners page.

How do I use Signal Path?

In the footer of the Roon application window, there is a little colored light–it might be yellow, green, shining blue, or bright purple.

Click the light, and you’ll see a pop up with a depiction of the path your audio is taking. If you are playing to a hardware device that Roon recognizes, you will also see some information about that product. The popup looks like this, and there are some more examples at the end of this article:

What do the lights mean?

It’s pretty simple:

 Bright Purple: Lossless

Lossless is exactly what the name implies: that the stream is going from the file to the device without being modified.

Shining Blue: Enhanced

Enhanced signal paths are indicated by a shining blue light. This means that Roon is performing some signal processing steps on the audio because you asked for them. The most common reason for a blue light is that features like Volume Leveling or DSP Engine are in use.

  Green: High Quality

Generally Signal Path will show the green light for OS Mixer outputs, as well as things like conversions for compatibility, and DSP volume. More on that in the examples at the end of this article.

  Yellow: Low quality 

Don’t worry, we’ve grabbed those MP3 bootlegs before, too, but technically speaking they’re not high quality. You’ll see the yellow light when lossy file formats are involved.

Some Examples

Lossless

Lossless signal paths are pretty boring–there just isn’t much to look at if no-one’s touching the audio stream. This example is one of the more interesting ones possible in Roon, because it identifies two separate devices that are involved in the playback chain.

Enhanced

Enhanced signal paths are indicated by a bright blue light. This means that Roon is performing some signal processing steps on the audio because you asked for them. The most common reason for a blue light is that features like Volume Leveling or DSP Engine are in use.

This is an example of an enhanced signal path. You can see that Volume Leveling is enabled, and sample rate conversion has been configured using the DSP Engine.

High Quality

There are a few scenarios where you might see a green light in your Signal Path. You might see green lights when the OS mixer output is being used, there are conversions for compatibility being performed, or DSP volume is enabled. Some examples of each are below.

OS Mixer Output

While the Mac software mixer does not do anything too gross, it might be performing software-based volume adjustments or sample rate conversion before playing the audio. As such, we can’t guarantee that the output quality is lossless, so we label it as “High Quality”.

Conversions for Compatibility

In this example, 192kHz audio is being converted to 96kHz audio because that is the maximum rate supported by this Meridian device. This is an extremely high-quality conversion, with virtually no audible loss in fidelity, but it wouldn’t be right to portray it as “lossless”.

DSP Volume

Enabling DSP volume inserts processing steps into the playback change that interfere with lossless playback. There’s nothing wrong with this: Features like this also bring great value! We are just trying to keep things honest.

Also note that in this signal path, the volume adjustment is actually happening outside of Roon, inside a Roon Ready device.

Low Quality Signal Path Examples

In this case, we’ve labeled this Signal Path as low quality because the source material is an AAC file. For the most part, if you see a yellow light, it’s because a lossy file was involved.