Digital Audio Interfaces

Digital Audio Interfaces

Digital Audio Interfaces and Formats – What gives?

In the 1980’s, as digital audio was in its infancy, manufacturers developing hardware had no choice but to create their own digital formats. Unfortunately, this meant the devices were incompatible, so none could be connected to each other. This is why there were so many formats such as AES/EBU, S/PDIF, ADAT, TDIF, MADI, AES3-id, and several others.

What is a Digital Interface?

Since different digital formats were incompatible when directly plugged into each other, the market was soon demanding a way to help these devices communicate. Digital interfaces provided a solution that could be connected between the devices and internally convert, or translate them into the same format. Now you could utilize devices from different manufacturers together without being plagued by previous incongruencies.

What is AES/EBU?

In 1985, to try and solve the issue of digital formats, the Audio Engineering Society (AES) and European Broadcast Union (EBU) created 2 open-source digital interfaces for stereo and multi-channel audio. These are commonly referred to as simply “AES” or “AES3” and “MADI” (Multi-channel Audio Digital Interface). The AES/EBU format made the transition to digital audio feel less foreign to users since it utilized a standard and familiar XLR connection, which was also cost-effective since no proprietary connector was needed.

What is S/PDIF?

Sony and Phillips entered the digital audio realm with a domestic format of their own, S/PDIF, which utilized both coaxial (phono) and Toslink (optical) connections. The auxiliary information and metadata for AES/EBU and S/PDIF differ slightly, but the audio formatting is the same, meaning both can be interconnected without much trouble.

What are “bits” and “kHz”?

Bits are the basic unit of data when transferring digital audio. Bit depth refers to the dynamic range while bit rate refers to the speed and playback quality. Kilohertz, or kHz, refers to bandwidth and is related to the speeds of bits per second. Greater bandwidth means faster data speed overall.

So let’s say you’re trying to connect a pair of Edifier R1280DB speakers, which use S/PDIF, into an Allen & Heath Qu-24 Digital Mixer, which uses AES/EBU. What would you need between them in order to make that connection work?

Compatible Audio Interface Products

S/PDIF Optical (Toslink) to AES/EBU

The Hosa ODL-312 is designed to take S/PDIF Optical to AES/EBU. This is a 2-channel interface that can do simultaneous conversion in both directions if required, and supports up to 24-bit/96 kHz S/PDIF audio.

S/PDIF Coax (RCA) to AES/EBU

The Hosa CDL-313 is designed to take S/PDIF Coax to AES/EBU. This is also a 2-channel interface that can do simultaneous conversion in both directions if required, and supports up to 24-bit/96 kHz S/PDIF audio.

*Be aware that these are digital format converters, not to be confused with analog-to-digital converters, which function very differently.

To learn more about the Hosa digital interfaces and where to purchase, follow the link here.

Hosa

History of MIDI

What is MIDI?

By textbook definition, MIDI is an acronym for Musical Instrument Digital Interface. It’s an electronic standard used for the transmission of digitally encoded music. But what exactly does that mean?

MIDI isn’t a sound or an instrument, it is simply the carrier for messages that specify the instructions of music. For example, if a chord progression is laid down via MIDI, those same chords’ notes, velocity, vibrato, panning, tempo, and pitch can be transmitted to an instrument that has MIDI capabilities.

Every time a musician plays a MIDI instrument, the exact way the musician played is transmitted into MIDI data. That data can then be transferred to a computer and played the same exact way through another MIDI instrument.

When Was MIDI Invented

In 1981, Dave Smith of Sequential Circuits, presented a paper on the “Universal Synthesizer Interface.” Just two years later, in 1983, at the winter NAMM Show*, a Sequential Circuits Prophet-600 was able to talk to a Roland Keyboard over a 5-pin cable.

*Fun fact, Hosa’s first NAMM Show appearance was just one year later, in 1984.

But in those days, polyphonic synthesizers cost thousands of dollars and one could really only get their hands on one if they were wealthy. So, Dave Smith came up with another idea; an interface so simple, inexpensive, and easy to implement that no manufacturer could refuse it. Smith helped develop it — but at the time, MIDI was widely viewed as “too slow” by peers and industry leaders… until it wasn’t.

The MIDI Manufacturers Organization (MMA) would not back down. In an industry of intense rivals, the MMA was able to hold a coalition of the most competitive manufacturers of the time. The message became clear: if MIDI is successful it would drive the industry into even greater success. The MMA was right, manufacturers were on board and immediately helped educate the market on MIDI through books and even online materials such as “Introduction to MIDI.”

MIDI Cables

MIDI cables help connect to MIDI devices. MIDI devices range from instruments, modules, computers and much more.

Hosa carries affordable and reliable midi cables in singles and doubles (for the in/out pair), we offer right angle MIDI, and we even have a MIDI to USB interface.

MIDI Interfaces

MIDI interfaces changed the way the world makes music. No longer did someone have to be in a luxurious studio to lay down guitar tracks or vocals. With the development of MIDI interfaces, emerged the concept of a “bedroom producer” — leveling the playing field for musicians across the globe. And when a “bedroom producer” wins multiple Grammys, it’s hard to justify the reason to even use a studio.

MIDI Today

Now, MIDI is everywhere. Initially just an idea that separated sound from a keyboard, it is now built into the least expensive keyboards to the most expensive studio gear. And, until just recently, the spec remained at version 1.0. MIDI data is responsible for nearly all of the music made today and, more importantly, helped lower the barrier to entry for music production. Instead of acquiring multiple instruments, use MIDI devices and simply pick out whatever sound you want. 

If you want to learn more about MIDI, head over to hosatech.com and get started using MIDI today!

- Hosa

Future Proof Your Network

Category cables have been in use for a number of years. Most consumers will know these as network cables, Ethernet cables, or possibly even Cat-5 cables. However, they may not understand what Cat-5 means or how to determine if that is really the cable in use. Category cables have been upgraded multiple times and the vast majority of consumers are probably using Category 5e cable in their home networks. As our networking needs have increased, so have the cables, and a change is already underway to go beyond Cat-5e.

Category cables are designed to transfer data within networks. They are the standard method of connectivity for Ethernet networking. Cat-5e is still the most common cable but it is close to its limits. In fact, larger networks requiring higher bandwidth and better interference protection have already abandoned 5e. We are demanding more from our networks, transferring more data at faster speeds than ever before. In addition to Ethernet networking, category cables can now be used for audio and video networks. Dante audio networks transfer uncompressed multi-channel audio via category cables and HDBase-T promises to be the future of home audio and video integration. HDBase-T transmits high-definition audio and video, Ethernet, device control signals, USB data, and power all through one category cable. Category 5 cables cannot handle this much data.

In order to meet the bandwidth needs of newer networks, we must use Category 6 cable. Category 6 improves bandwidth and crosstalk protection over previous generations of category cable. It has been tested to perform up to 250 MHz and can transmit 10 Gigabits per second (Gbps) for up to 55 meters. This is not to say it cannot go beyond these points, only that this is how the cable was tested. Category 6 cables also have several shielding options. You can purchase cables in the more traditional Unshielded Twisted Pair (UTP) construction, or with shielding around each twisted pair, the full cable assembly, or both. Hosa’s CAT-600BK series is an example of Category 6 cable with both shielding around each twisted pair and around the entire assembly.

In addition to the original Category 6 cable, a revision to the standard later added Cat-6A cable, also known as Category 6 Augmented. This cable provides even better protection against crosstalk and has been tested up to 500 MHz. Cat-6A can run 10 Gbps Ethernet up to 100 meters.

It’s important to note that while Cat-5e was the updated version of the original Category 5 standard, there is no Cat-6e version recognized by ANSI/TIA.

The good thing about category cables is that they are backward compatible. If you are setting up a new network, it is a good idea to use Cat-6 cable even if you do not believe your network will need the added bandwidth. Taking that step now should make things easier in the future.

- Jose

How to Properly Connect the DB-25 Jack on Your Audio Device

Many times, people look at the jacks on the back of a device to figure out what cables they will need. While this is not really the best way to figure things out, most of the time it will get results. If you see an RCA jack and ask for an “RCA cable”, you’ll probably find a suitable cable (though there are different types of cables that use the RCA connector). But if you don’t get a little more information, you’ll most likely run into trouble when you see a DB-25 jack on the back of your audio device.

DB-25, or D-sub, connectors were originally created for computer applications. The audio industry adopted the DB-25 as a way of getting multiple channels in and out of devices while taking up minimal space. In this regard, the DB-25 connector works great. However, the use of this connector is problematic because there is not one universally accepted way of wiring it. In fact, there are three widely used wiring conventions when it comes to DB-25 in the audio world.

Some devices use D-sub connectors as a way of inputting or outputting eight channels of balanced analog audio. Each balanced channel requires three pins—one for the positive signal, one for the negative, and one for the shield—and each channel is grouped in a triangle pattern by taking two pins from one row and one pin from the other. Eight channels require 24 pins and pin 13 is simply not used. The Hosa DTM-800 series balanced snake is wired this way. It connects to the DB-25 output and breaks out to eight XLR male connectors. The Precision 8 mic preamp by True Systems uses a DB-25 connector to output all eight channels. This makes it possible to run a single cable with eight channels to an audio interface or mixer.

Professional audio devices can also use one DB-25 connector for eight channels In & Out (I/O) using the AES3, or AES/EBU, format. This digital audio format enables devices to send two channels of audio along one balanced audio line. This is where it really gets fun, as there are two standards for AES/EBU multi-channel I/O—and manufacturers choose which one to use.

The first is known as the Tascam wiring standard. The Tascam wiring standard is the same as the analog standard at the DB-25 connector end. The wire, however, must be different, as it is not passing analog sound. The AES3 specification requires 110-ohm balanced cabling for AES/EBU signals. Unlike analog snakes, AES/EBU snakes carry two digital channels on each balanced line. This means through one DB-25 snake, the device can send eight channels and receive eight channels simultaneously. If you are using a digital snake that breaks out to XLR connectors, it will have four male and four female XLR connectors instead of four like connectors on the analog snakes. Avid and Universal Audio are two companies using the Tascam standard. Avid’s ProTools HD I/O uses AES/EBU via a DB-25 jack.

Companies such as Apogee and Mackie, among others, have adopted the Yamaha wiring standard for their AES/EBU I/O. The wire is the same as that used for the Tascam digital snakes but the pin configuration is much different. In this case, the ground wires are on one side of the connector, while the other side gets the conductors. The Lynx Aurora 16 AD/DA converter uses AES/EBU with the Yamaha standard.

Note that if you are connecting two digital devices, you must make sure to use the correct pinout for each. If one of your devices uses the Tascam standard for its AES/EBU I/O and the other uses the Yamaha standard, you can still use them together. You must, however, use a snake with the Tascam pinout on one end and the Yamaha pinout on the other. Analog to digital is not as simple. You cannot use a DB25 snake to interconnect AES/EBU and analog signals. This would require a separate interface, which is a topic for another discussion.

The next time you turn to the back of your device for cable answers, remember the connector type is not everything—especially with DB-25. Your first question should be whether you’re looking at an analog or digital connection. If it’s digital, the next step is to figure out the wiring standard the device uses. Taking these steps will decrease headaches down the road and ensure you purchase the right DB-25 snake the first time.

- Jose