Category: Networking

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Network Switches for location

You can’t have your cake and eat it

Location requirements

I’ve had a number of people ask me about network switches over the last week or so. More mixers seem to be looking at Dante on set in various configurations, however most of the switch manufacturers don’t exactly have us in mind when designing products, so we’ve got to make compromises.

Things we need/want:
No disruption using AoIP protocols, like Dante, AES67 etc
Silent (usually fanless)
12V DC powered
Fast boot up
PoE distribution

I’m not aware of any switch which necessarily ticks all the boxes, but there’s quite a few which will tick some.

Managed and Unmanaged Switches

As far as best practice goes in putting together a Dante network, a lot of the choices made can only be done using managed switches, especially if anything which isn’t Dante is on that network.

One of the key functions of managed switches is Quality of Service. This prioritises certain traffic (with the most important being the clock). It’s recommended by Audinate to implement this if there are any slower 100Mbps devices (like the small ones which use an Ultimo chipset) on the network.

Another is IGMP Snooping- this only comes into play if multicast sends are being used, as it limits the number of destinations the data is sent to and reduced the overhead on the switch.

If there are only a few gigabit devices (not small ultimo devices!), without much traffic then an unmanaged switch should be fine. The main thing to look out for is if it has ‘Energy Efficient Ethernet’- this can cause a Dante network to fall over, so you don’t want this feature and if it’s on a managed switch make sure it can be turned off.

Audinate and Shure both publish lists of switches which are not recommended.

A drawback of managed switches can also be boot time. The more switches seem to do, the more complicated the operating system. Some can take a few minutes to boot up, which really isn’t useful if you’ve just had a power outage.

Power over Ethernet (PoE)

Power over Ethernet isn’t quite as straightforward as you might think. There are multiple standards, which use different pins and some have handshake methods with the other end before turning it on. You need to check the standards required of the boxes you’re plugging in, they won’t work with every switch and different switches have different capacities

The basic 3 standards are:

PoE – this can be very vague, from a power source being plugged into some of the wires on a CAT5 cable. The base standard is 802.3af, which uses 48V to carry up to 15.4W of power on one network cable

PoE+ or 802.3at. This allows up to 30W and runs at 52V

PoE++ or 802.3bt This is the big one, either 60W or 90W. Also needs a juicy power source

Cisco also do a proprietary UPOE+ method which appeared before 802.3bt was standardised.

It all needs a high voltage and in some cases can carry quite a lot of power. This means that if equipment is running off 12V; it needs to be stepped up somewhere with a DC-DC converter.

PoE doesn’t have to be implemented at the switch, however. It can also be added with a PoE injector. This is useful if there’s only one or a couple of devices which need it.
I’ve sourced some cheap 10W injectors which will step up from 12V: https://rtsound.com/collections/power-over-ethernet/products/48v-10w-poe-injector-with-voltage-step-up-from-10-24v

Planet make some industrial 802.3bt injectors which will step up from 12V

Some switches can be powered by PoE and some can then pass that on. They’ll never be able to pass on all of the power; don’t take either as given. “PoE PD” (PoE Powered Device) is often a term used.

Some Commonly used Switches

Cisco SG350-10

This is the ‘industry standard’ managed Dante switch. Audinate commonly use them and multiple manufacturers make guides to setting them up.

They’ll do everything you need management-wise.

They can output PoE+ and proprietary 60W UPOE+ and it’s possible to power a second switch with the first and pass through PoE+

They have SFP optical ports, which can be used for very long cable runs.

However- they need 54V. I’ve made a solution for this with a step up converter. This can also be adapted to other switches and the voltage tweaked fairly easily:
https://rtsound.com/collections/power-over-ethernet/products/dc-power-supply-for-cisco-sg350-and-sg250-poe-switches

It takes around 90 seconds to boot up, which doesn’t seem to be able to be got around. If there are 2 switches being powered by each other, that’s almost 3 minutes to get the remote switch up. And it’s been discontinued- it’s replacement, the CBS350 apparently takes even longer!

Netgear GS105Ev2

This is a bit of an unusual choice, as Netgear GS – E switches appear in the Shure Disqualified list. It is, however quite a commonly used switch as it’s small and can be powered by 12V.

Personally I’d be a bit wary of using this without knowing exactly why it’s on a disqualified list. It’s only the v2 version where Energy Efficient ethernet can be turned off (I believe it is off as a factory setting).

I have seen recommendations to turn off IGMP Snooping too as it apparently doesn’t work properly with Dante. This may also be the reason for its disqualification.

Trendnet TI-PG62B

This is an industrial unmanaged switch, which has the holy grail of PoE+ and the ability to run from a 12V supply.

It has 4 PoE+ ports and 2 SFP ports.

Planet also make an 8+2 port 12V industrial switch.

Other Choices

Having had a look around, Cisco do make managed industrial switches. They’re really not cheap and some are still limited to 100Mbps and require a separate DC PSU to step up.

Another expensive remote option could be Cisco’s Catalyst Micro Switch series, which are small, managed layer 2 switches.

Luminex make switches especially for live sound and video with neutrik ethercon connectors and come pre-configured, however they only have AC powering options.

Netgear make their M4250 series switches specifically for Audio and Video and can come pre-configured for Dante. Again, AC power only…









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Adapting a network switch for location use

View of the switch in the rack

What do you need one of those for?

We’re starting to see more useful products using audio over IP, all of which need switches to connect multiple devices together. This is effectively a patchbay for these devices, however the routing is determined in the devices themselves, while the switch is effectively the patch cables sending the data to and from the right destinations. Here’s an overview of what a switch does and how it works: https://www.oreilly.com/library/view/ethernet-switches/9781449367299/ch01.html

Specifications

I’m mainly going to be using this one using Audiante Dante, which is a proprietary audio over IP system. This will work using most off the shelf switches, however they do recommend using a managed switch, especially if there’s going to be other data on the network. It need to be able to carry gigabit ethernet, supply power over ethernet, have over 5 locking ports and run off 12V DC power. And not make any noise.

Unfortunately I couldn’t find any switches on the market that fulfilled all those specs, so I’ll have to adapt one

Starting points

To begin with, I need a switch. One that ticked most of the boxes was the Cisco SG250-08HP. The Cisco SG250 series seem to be one of the more frequently recommended switches used for Dante networks. This is the smallest one in the series which can supply PoE. However, it comes with a (rather hefty) 52V PSU. It also doesn’t come with ethercon connectors, they seem to only be on some more specialised switches for the AV industry (all of which seem to have mains supplies)

Power

In order to get the switch to run off 12V, it needs the voltage to be increased with a DC-DC Converter to something approaching the 54V specified on the input of the switch. I say approaching, because I had a 48V DC-DC converter which I’d previously been using to power another PoE switch. It also already had the Kycon KPPX-4P connector on and had the same wiring (which is fortunate as that took some finding…).

I’m not sure exactly what the power draw of the switch is, however it can supply up to 45W of PoE. The mains power supply which comes with the switch is just short of 60W (54V at 1.1A).

The DC-DC converter I’ve used is only 40W at 48V- the switch seems to run fine on it though, however there isn’t enough power to run the full capacity of PoE devices. There is a bigger 60W model, however it is bigger and may be difficult fitting it into the case.

Casing

My intended use for this is to mount it on a Soundcart MiniCart. This has 10.5″ ‘half rack’ mounting points, which seems to be a ‘half-standard’, as there’s another 9.5″ half rack spacing. This seems to work with most boxes which are designed to be mounted side by side in a rack by putting both rack rears on the same box, although they’re not really designed for this.

I’ve used some off the shelf parts from a metal fabrication company, however there were a few issues getting things to fit- all 8 ethercon ports won’t fit on the panel and still get in the enclosure- and the 4 pin power connector just fits, with some filing down of the sides! The case itself is steel, so has a fair bit of weight to it.

Connectors and Cables

I opted for the ‘feedthrough’ ethercon connector as otherwise there was a lot of soldering involved. I also realised that regular moulded RJ45 cables wouldn’t fit in the chassis, so had to swap them out for low profile flat ones. This put the build of this back a week. These are probably less hardwearing, however won’t be moving about in the chassis.

I did consider some of the more weatherproof connectors, and even bought some flip down panels– however they were fouling each other when packed together that densely. Given there are holes in the chassis for airflow (which the switch and PSU will need), it seemed a bit much fully weatherproofing the connectors, which would have added further cost

Layout

It ended up all being a bit tighter than expected- I originally imagined the switch ports behind the ethercon connectors. This way, however does allow you to look through the side vents to see LEDs

It all fits together like this

I want one!

I’ve had a few expressions of interest in people buying these- there might need to be a bit of refinement of the metalwork, including a little more space and an extra output for the 8th port. This is currently a prototype but let me know if you’re interested in one- it’ll need a few refinements, but I could potentially get a run of these put together. Back of an envelope costs are around £300+vat for the whole thing

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‘One cable’ audio networking connections for analogue devices using PoE

Why?

I’m looking into running out a single cable to connect a box to an audio over IP network. For example, a transmitter or receiver to cover a separate area. There are a number of different AOIP standards, which include Audinate Dante, Ravenna and AVB- this is mainly a demonstration of physical connections, but different hardware may be required for different networking standards. This method can be scaled up to devices with more analogue/digital inputs and outputs as long as they can be powered.

Ingredients

You need the following:
Target device with a DC power input (in this case a Sennheiser SR300 G2 transmitter)
Network switch with power over Ethernet (PoE) (Cisco SG250-08HP)
PoE or DC powered AoIP to analogue endpoint (Dante AVIO)
Passive PoE switch (Linovision mini passive switch)
12V PoE Splitter (I used this)
CAT5e cables (or better)

Setup

Here we have the main PoE switch connected to the passive PoE switch, which powers that, which in turn powers both the Dante AVIO and Ethernet splitter. The Dante AVIO runs to 2 XLR outs which plug into the Sennheiser transmitter and the PoE Splitter feeds 12V to the transmitter. It powers up as soon as the main switch has booted up. The PoE Splitter also has an RJ45 connector on. If this was a G3 or later Sennheiser transmitter, this could connect to the data port and the transmitter’s settings could be accessed over the network.

Things to bear in mind

Everything in the network needs a certain amount of power and the PoE switch can only supply a certain amount (usually at 48V). Check the specs for power consumption of devices. Ohm’s law is useful for calculating current at different voltages

Look at the required voltage and current for the device you want to power. Voltage has to be within the specified range, while the supplied current can be more than specified (devices only draw as much current as they require). Check that you can find a PoE splitter that fits these specifications.

There are different PoE standards, the current ones are 802.11af or 802.11at which supply different amounts of power per port. Some things which just say ‘PoE’ without a standard may not play nicely or even damage equipment.

There will be some loss of power through the cable. The reason the voltage is reasonably high (48V) is to reduce the current and associated loss due to heating the cable- the longer and thinner the cable, the greater the loss.

The passive switch used here is only 10/100Mbps, this is fine as the Dante interface is also this speed, but if more channels need to be passed though a 10/100/1000 switch may be required

Your DC powered device may have a different connector to the splitter- it’s possible to chop off the moulded connector and solder on a different one

What’s the passive switch for?

In this case the PoE Splitter converts all the power on the port, so it doesn’t pass through to the RJ45 connector, so 2 network ports are required. This also shows how this could work with a box with a separate network port for control. Bigger passive PoE switches are available, so multiple interfaces could be run from one long cable. All this stuff can go in the back of a rack case with a more robust ethercon connector dealing with the connection with the main switch on a long cable.

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Audio Interfaces as Location Mixers 2: Motu AVB Midi to OSC

Earlier this year I made a post about the theoretical use of audio interfaces as digital mixers.  Since then I’ve got some toys and the experiments have begun:

Motu 8D

I ended up getting a good deal on 2 of these interfaces.  They each have 8 channels of AES3 audio in and out with sample rate conversion, although some of the connections are 75ohm RCA for consumer SP/DIF.   They are also happy with a variable voltage range and are happy with reversed polarity on the DC input (even though the plug says 15V centre positive).  The AVB connection allows them to link together and address multiple channels from one interface, essentially making a modular interface with all sorts of connections.  Together they have 16 inputs and outputs.

Control Surface

I started off here running a Keith McMillen K-Mix, however it just runs standard midi control change and note outputs.  These are easy to deal with and re-route, however I came across some issues with resolution which were solved by using a control surface that runs the Mackie Control Universal protocol (MCU).  The cheapest one I could find was an iCon Platform M.

Lost in Translation

The problem with the MOTU interfaces in this instance was that they used a nice control protocol for computers to talk to each other, but not control surface hardware- they’re designed the interface with the view that it’s used on an ipad or similar.  They use Open Sound Control to communicate (documentation here), so there needs to be a way of converting midi commands to this.  It’s also one way- the interface doesn’t send any data back.  So, I needed a way of translating midi commands to OSC.

Pure Data

After looking at a few solutions, and realising I can’t program properly- it dawned on me that I could use Pure Data.  It’s an open source graphical programming language (similar to the proprietary Max/MSP) and I’d used it before on various music performance projects.  It would also run on a raspberry pi– so could have a low power dedicated computer to do the translation work.  I found it was actually pretty straightforward to get the midi in and the OSC out, however came across a few snags…

Linear faders

This is one of those terms where everything gets confusing.  Yes, linear faders can mean they’re in a straight line- rather than rotary faders, which you turn.  The potentiometers, however need to be logarithmic- every 3dB of attenuation is a halving of voltage.  In most midi applications this would normally be done at the software end, but here it’s just a number being fed in.  In order to do this a bit of mathematical transformation of the data was required and the higher resolution of the faders really helped in MCU (they’re used as pitch bend controls on each channel).

Mechanisation

In order to run 16 channels from an 8 channel controller I decided (possibly foolishly) to create a second layer on the PD patch and send back data to the control surface.  It works, however the mute and solo buttons unexpectedly turned out to be a headache!

IMG_2648

Wot, no Dante?

I had a look and I couldn’t find and DC powered interfaces with a Dante connection and a mix engine.  Best option I can think of is to use a MADI interface (such as a MOTU M64 or RME Madiface Pro) and a Directout Exbox.md or Ferrofish Verto series converter

Talkback

I haven’t put a dedicated talkback control in yet, but should be a case of pressing a button to open a fader.  There is a dedicated talkback button on the newer Motu 828es, however- although it only has mains power

I Want This

If you want to have a go with it, please feel free to get in touch.  I can’t offer any kind of warranty or technical support at the moment- it’s just a thing I made.  It should hopefully work with any of the Motu AVB interfaces and midi controllers with MCU emulation.  It requires pd-extended 0.43-4 to run