Audio over IP

There are several ways to move many channels of audio over a hundred meters. Most familiar to any that have worked in live sound is the humble audio snake. These are bundles of parallel runs of wires, with 1, 2 or 3 wires per channel. But over the last decade or so, there's been an enormous amount of innovation around ways to carry audio over ethernet. 

Dante (Digital Audio Network Through Ethernet) is a way to move many--up to 1024 uncompressed channels of audio--over a single ethernet cable with incredible reliability and redundancy. Latency is extremely low (sub millisecond), and each endpoint maintains its own clock, meaning the latency at each endpoint can be tailored. This is important in large live sound settings where physical distances can wreak havoc with time alignment. 

The larger picture for Dante is that you have lots of audio sources (transmitters) and sinks (receivers). Each of these is connected to the network, and a piece of software on your PC known as a controller allows you to send any transmitter to any receiver or even multiple receivers. So, for live audio, you take all your mics and instruments, plug each into a mostly standard ethernet router and you can then specify in the controller where those packets should all go. For example, they could all go to a front-of-house mixer, and some might go to both the FOH and monitor mixer. The mixed signals could then be sent to speakers over the same ethernet.

And increasingly, we're seeing the input and output of devices speak Dante. So, there is a role here for testing over Dante. 

We'll do this using the QA401 and the following pieces:

Dante AVIO Digital Output Adapter This is basically an ethernet to DAC box. This box is plugged into a PoE hub.  Price is about $120. In the Dante world, these allow you to connect legacy equipment to the network. For example, if you had a powered speaker with an analog input, you'd use this output adapter to make it Dante-ready. There are ethernet to ADC boxes too, as well as speakers with an ethernet ports (Dante) on the back, amplifiers with Dante inputs. It's a very strong ecosystem with a well thought out silicon portfolio for making existing devices (such as microphones) Dante-ready.

5 Port Gibabit PoE Switch This is a simple ethernet switch with 4 powered ports. These ports follow 802.3af, meaning 48V is provided on the ethernet port, and that is used to power the Output Adaptor above. Nothing too special is needed, and off the shelf stuff will work fine for most setups.

Dante Virtual Soundcard This is what makes Dante work out of the box with the QA401. This software makes the Dante devices appear as a standard sound card. And since the QA401 will use your primary sound card as the "mirror" device, this piece of software can be used to test any Dante receiver. This costs about $30 from Audinate.

Dante Controller This software runs on your PC and lets you configure how all the various receivers and transmitters will talk to each other. This software is free from Audinate.


The setup described below is working via "mirroring". This is a mode on the QA401 where the tone you specify for Gen1 (frequency and amplitude) is "mirrored" out the primary soundcard in the system. You can test Dante receivers using this approach, but you can't test Dante transmitters. 



To set things up, we first plug the Avio output adapter into the PoE switch. And then that is plugged into the test PC ethernet port. 

Next, install the Dante virtual soundcard and set it up for WDM audio:

Next, in the controller, specify you want Channel 1 on the PC to connect to the Receiver you plugged in above. With WDM, you will get 16 channels of audio. 

Then go into your Sound Settings in Windows and find the Dante Virtual Soundcard and set channel 1-2 to be the default audio device. This is how the QA401 knows what soundcard to use:

And at this point, you have set up the Dante side of things. Next, re-start the QA401 and go into Settings->Options->Other and enable Mirroring

With the output of the Dante receiver connected to the input of the QA401, we can switch into dBFS mode and set the generator to -1 dBFS and Enable Gen1:

And then, you should see a tone on the display. This is the tone being generated by the Dante receiver (this is a fully differential measurement--that is, the Pin2 of the XLR goes to the L+ input, and Pin3 of the XLR goes to the L- input).

Note in the plot above we've switched back to dBV, but we're still generating at -1 dBFS from the Dante receiver. And with -1 dBFS input, we see we get about 0.7 dBV out, or about 1Vrms. 

Now, we have an option from the Dante controller to adjust some settings on the receiver. One option is to move from the default +4 dBu to +18 dBu (12 dB higher). Let's do it:

That adjustment requires the attenuator to be engaged on the QA401. After doing that, we're met with the following. Note the peak is now 14.16 dBV.



Measuring Dante audio receivers should be pretty straightforward using the QA401 software. Dante is very easy to setup. And by making it your default sound card, you can be making basic measurements just as you would a DAC. 

Happy experimenting!

PS. This post can be discussed on the forum at the link HERE.

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