A Plea for PoE

Ever since music festivals became the primary medium for electronic music, live performance has become more about the giant spectacle of screens, lights, and fire. The musician becomes a mere speck on the stage, only there to make the audience feel like they're not just paying for a pre-programmed lightshow and a playlist¹. CDJs and laptops lock the performer to one position, and limits the dynamism and physicality of their performances. Heck, it's called Electronic *Dance* Music, but the vast majority of DJs don't do much more than bob their head, pump their arms, and clap their hands (TODO: write an article about how throwing a cake is the most innovative dance move ever performed by a DJ). It's great that electronic music has given lighting and effects operators the freedom to unleash their craft on the world, but I can't help but compare these shows to more musically performative events like rock concerts and drum circles, and wonder: what could it look like if today's instruments were better at expressing today's music?

I do want to emphasize: it is not the music, the musician, or the stage that is in need of reform. There is plenty of musicianship and creativity in electronic music today; arguably more than there was for rock and classical. Rather, it's the limitations and hassle of the hardware that restrict how that music can be performed. Perhaps a laptop is effective and convenient enough for the production of music, but I don't see a future in laptops as a tool for performance.

Anecdote of a musical stage perforance

I recently helped out with a few showcases for a local multimedia festival. One such showcase brought in a bunch of musicians of various genres one after another. One band had 5 members and a drum kit that had to be moved on and off, while one had just a laptop and a microphone². Now, between the two, you would think that the laptop would be a lot easier, right? Contrary to what I had expected, technical difficulties with the laptop put the whole schedule back almost an hour. A dongle was lost at some point, cables had to be switched out, devices had to be restarted; a textbook example of Murphy's Law. And this was on top of the already cumbersome setup process of taking each device out of a suitcase and plugging in the various power and USB cables. Once it got started, though, the performance was really cool!

The rest of this blog post presents a case for Power over Ethernet, a technological standard that I think is underused in music hardware today. I can't guarantee that it will solve all of these problems, but if there's anything I've learned from those last few days of stage work, it's that electronic music performance setup processes are in dire need of simplification. In its current state, using a laptop on stage with its tangle of cables going to MIDI controllers, audio interfaces, and power supplies is a complicated problem, solutions for which are very fragile (compared to setups for other types of music performance). My goal with this manifesto is to convince music hardware manufacturers to simplify the experience for electronic musicians performing their music, and provide them with the resources to make it easy to do so.

Crash course on PoE

Power over Ethernet (PoE) is a set of standards for, as you may have guessed, sending power over an Ethernet connection. Similar to USB-PD, the devices negotiate power, and both sides have to be compatible with the standard. If one side does not support it, the communication channel falls back to the default, which is 5 volts 0.5 amps (2.5 watts) for USB and no power for Ethernet.

As a disclaimer, PoE is competing against plain USB for most music hardware, but if you want something like a built-in speaker or motorized faders or LEDs out the wazoo, you'll want more than the 2.5 watts that regular USB is rated for, which will require some sort of external DC power supply, whether that's a barrel jack wall wart, USB-PD or PoE (or just crossing your fingers and hoping that your USB 2.0 host can provide more than 0.5 amps).

In all my reading, I was only able to find three "canonical" applications for PoE: security cameras, IP phones (phones that communicate over the internet rather than cell networks), and commercial wireless access points. Hopefully we can change that.

PoE vs USB-PD

So why PoE?

Despite USB being a better standard for 90% of applications, there is still a reason that Ethernet dominates the networking industry. The two main benefits that I can see are: cables are extremely cheap (and easy to crimp yourself), and can get extremely long. With USB 3.0 (using 26 AWG wire), you get approximately 3 meters maximum³. Even with the lower-bandwith USB 2.0, you get only get 5 meters^[4][5]. On the other hand, Ethernet cables (of any Category) are generally rated for 100 meters.

I believe this extra length is absolutely vital for making digital music controllers more performable. With USB, the musician is tethered to a circular area with a radius of 5 meters, but with Ethernet, the laptop doesn't even have to be on the stage. It could be setup somewhere out of the way and left alone between performances, which would have almost certainly prevented the issue with the laptop in the anecdote from earlier, since you could have all the equipment set up before the show starts, or at the very least, start setting up before the previous band is done. Or you could go as far as to have a rack-mount desktop, connect it to a PoE switch, and run a single ethernet cable to each musician and move around with the same freedom that an electric guitarist might have. Just one cable between the musician and the sound system.

While I don't know of any hardware that uses PoE specifically, there are plenty of open standards for audio over an Ethernet connection, often used to send many channels of audio over a "digital snake" from a stage to its sound booth and back. It isn't strange to see a roll or two of Cat 5(e) cable in a live venue's arsenal.

Some Pioneer CDJs and mixers are equipped with Ethernet for a feature that they call Pro DJ Link. Among other things, it connects any attached filesystems to other devices on the network, and can send the audio to a laptop (also on the network) with the appropriate software. I only know about this because during the aforementioned showcase, anytime there was a DJ accompanying the vocalist, the CDJs and mixer would be brought on stage in their flight case, (along with a Wi-Fi router and power strip), and setup was as easy as just plugging in the power and letting the booth take it from there. It was quick, easy, and went without a hitch every time.

The current state of DJ hardware connectivity is the future that I see for all music hardware: controllers, audio interfaces, rack-mount synthesizers, effects processors, eurorack, and anything other electronic device that can be used to make or perform music, all connected to one PoE switch offstage and nothing else.

One of the other use cases I've discovered recently is [Personal Monitoring Mixers]. These are apparently pretty common in studios and orchestra pits, and often (but not always) have PoE support. Unfortunately, they also tend to use proprietary audio over IP protocols, which I'm not too jazzed about.

Enter: Open Sound Control

By reading this far, you have just activated my trap card. For the past 3 years or so, I have slowly been coming to the conclusion that Open Sound Control (OSC) is the solution to almost all of my musical problems. Voice synthesizer plugin needs some way to receive phoneme info? OSC has character and string types. Want more semantically useful numeric types in a tracker-based DAW? OSC has single and double precision floats, 32 and 64 bit integers, booleans, infinity, timetags, and nil (if you count that as a numerical value). Need a file format that can express sample-accurate timing and namespacing? It's not standardized, but oscdump has a pretty reasonable output, and if that's not to your liking, you can just store the raw bytes, since time information is encoded in the packet (along with the message and its namespace, of course). Of course, OSC has its own drawbacks, so if you can do something entirely with MIDI, it's probably best to do it with MIDI. But if you need the length of an Ethernet connection anyway, you might as well use OSC as the transport layer for your MIDI data.

One of the notable things about OSC is that its designed to run on top of a network. Most OSC-compatible software asks for things like IP addresses and ports, and can communicate with OSC endpoints over the internet. OSC was made for Ethernet, and with the locking clip feature of RJ45 connectors (or optionally Ethercon), longer maximum cable length, and industry adoption of audio over Ethernet, PoE music hardware seems like it could be the "killer app" of OSC.

Implementing PoE

It's a bit tough to say authoritatively which is easier to implement between PoE and USB-PD from a hardware development perspective (focusing on the receiving end), as I've never implemented either.

That being said, I've spent a lot of my last few months looking at PoE, and it seems like the most simple way to go about it is using an RJ45 jack with built-in magnetics and a bridge rectifier (HY931147C or LPJ4112CNL), and a module like those offered by Silvertel, which total to about $15, which doesn't even include any of the parts you would need for the data part of ethernet. Certainly much more expensive than a USB-B jack.

If you're willing to get more DIY with it, you can break both the RJ45 jack and the PoE module up into their discrete components, for example with the following parts:

*: The RJ45 jack can be cheaper if you don't care about status LEDs or shielding

Approximating the generic parts (resistors, diodes, capacitors, inductors, etc) to less than $1 total, this comes out to under $4.34, which is still much more than the USB-B jack, but still managable for a high-end digital instrument.

TODO: finish

• espoir
  • https://docs.connaxio.com/doc/espoir_schematics_latest.pdf
  • https://github.com/Connaxio/espoir
• https://www.olimex.com/
  • esp32-poe
    • https://github.com/OLIMEX/ESP32-POE/blob/master/HARDWARE/ESP32-PoE-hardware-revision-L/ESP32-PoE_Rev_L.pdf
  • https://github.com/OLIMEX/ESP32-POE-ISO
  • https://github.com/OLIMEX/S3-OLinuXino
• wiznet pico
  • https://docs.wiznet.io/Product/Open-Source-Hardware/wiznet-pico-poe
  • https://docs.wiznet.io/img/osh/WIZnet_Pico_PoE/Sch_WIZnet_Pico_PoE_FIN.pdf
  • https://github.com/Wiznet/Hardware-Files-of-WIZnet/tree/master/08_OSHW/WIZnet%20Pico%20PoE
• chips
  • https://www.ti.com/power-management/power-over-ethernet-poe/powered-devices/products.html
  • https://www.st.com/en/power-management/power-over-ethernet-ics/products.html
  • https://www.ti.com/lit/ds/symlink/tps2375-1.pdf
  • https://www.analog.com/en/parametricsearch/11407#/
  • transformers
    • find the replacement for SM13117EL
• https://www.st.com/en/evaluation-tools/steval-poe001v1.html

Closing thoughts

Please let me connect the music half of my 19" rack to the networking half.

Footnotes

References

[1] https://www.netgear.com/business/solutions/poe/overview/

[2] https://www.tp-link.com/us/solution/poe/

[3] https://superuser.com/questions/1105242/how-many-volts-there-are-in-poe

[4] http://janaxelson.com/usb3faq.htm#ca_maximum

[5] https://blog.tripplite.com/usb-cable-max-length