Analog to Digital Conversion (S/PDIF Out) – M-Audio

Analog to Digital Conversion S/PDIF Solutions by M-Audio – Adding inputs to your computer audio recording interface without heading into bankruptcy.

So you’ve ordered that fancy recording interface that’s going to enable you to record eight simultaneous tracks of music… or so you think. But when it arrives you discover just six XLR inputs. I’m no mathematician, but I do know it is impossible for six XLR inputs to capture eight tracks at once with your recording program. So how is this interface able to advertise itself as capable of recording eight simultaneous tracks of computer audio? Well, this is possible due to the coaxial/RCA S/PDIF input on the unit that is labeled digital in. That’s right. It is a stereo digital input. The novice may at first be dumbfounded by this discovery. How is it possible to use this input? Well, it’s simple. You are going to need an analog to digital conversion preamp or standalone converter. An A/D converter will take the analog signal that you send it and convert it to digital, much like a computer audio interface does. Then you can simply send the digital S/PDIF out of the converter to the digital input of the recording interface and into your recording program. However, let me point out one thing. The coaxial/RCA digital input is not the only type of connector available. The other version is called an optical, or Toslink, connector. So you need to make sure the S/PDIF out connector of the A/D converter you purchase matches the digital input connector of the recording interface. It’s very simple really.

Image of Coaxial and Optical Digital Outputs on M-Audio Analog to Digital Conversion Page (S/PDIF Out)

Photo by Home Cinema Pictures / CC BY-ND 2.0

So where do I find one of these preamps or standalone converters for analog to digital conversion, and with an S/PDIF out? Well, they are widely available through many popular manufacturers such as Apogee, Lucid, and RME. But… do a quick search for some of these if you would like, for a good laugh that is. What you will find is a selection of analog to digital converters that each cost hundreds of dollars. Some of these even approach one grand! Now, this seems absolutely ridiculous to me. Why would I spend that much money to add two inputs to a computer audio interface that cost me under $200? Well, the quick answer is, I wouldn’t ever consider doing something so ridiculous. So, I researched. I quickly found a really cheap A/D converter with an S/PDIF out. It was from China, and I could get it for about $20. But I had a really bad feeling about this. So I continued to search. And I found two solutions, both manufactured by M-Audio. The first one is called The Flying Cow. It is a simple, no frills A/D converter that performs as advertised. I just plugged the outputs of my Mackie Mixer into the inputs of The Flying Cow. Then I connected the coaxial/RCA digital S/PDIF out directly into my computer audio interface. I had zero problems with this unit. However, eventually I was in need of some quick cash, so this beautiful unit had to go. But when it was time to get back to audio recording, I still needed the two additional inputs on my interface. So I had to either find another Flying Cow or go for something else. The only other price efficient converter I could find is the M-Audio Duo. This is a microphone preamp that also serves as a standalone audio to digital converter with a coaxial/RCA S/PDIF out. I have not come across too many preamps that have a digital output, so this one intrigued me. I was able to find one for a little over $30 on And I am equally as happy with the Duo as I was with the Flying Cow. And since this unit is a preamp in addition to an A/D converter, I do not have to use my Mackie mixer (although I still do just as a personal preference). I do miss the amazing M-Audio Flying Cow logo though. Maybe I can just print it out on inkjet sticker paper and affix it to the Duo. Yes, I do sometimes do things that are THAT ridiculous.

So if you need additional XLR inputs and you have a coaxial/RCA digital input on your recording interface, I would suggest either the M-Audio Flying Cow or the M-Audio Duo. Each has a coaxial/RCA S/PDIF out. Both of these products are discontinued, but used units can still be found fairly often. Check out the links below for more info and specs.

M-Audio Duo
M-Audio Flying Cow