As digital gear becomes more prevalent I see the same question asked over and over again, “Should I record using the analogue outs or use the USB (or S/PDIF) outputs?” The popular answer is, “keep it digital or you’ll lose sound quality!” Is there any merit to this claim that sound quality is lost if you do not “keep it digital” all the way? Does it matter in a home recording studio which you choose? Let’s find out.
The audio files
Following are three sound files. They are all a guitar playing through a Line 6 POD X3 Live. One take was recorded to three stereo tracks simultaneously using the USB driver for POD X3, the 1/4″ outs of X3 into the 1/4″ ins of an Echo Layla, and the S/PDIF out of X3 into the S/PDIF in of the Layla. There is absolutely no post-processing done on any of these tracks. Here are the files: sample A, sample B, sample C. You can guess Layla analogue, Layla digital, or POD X3 USB for each track. Email your guesses to [email protected]
Analogue versus Digital: Expected results
No “scientific” experiment is complete without stating your expected results. I have listened to the sound files myself in blind testing. With enough responses I fully expect there to be no clear winner. The real result I hope to achieve is the illustration that it does not matter. The gear of today is so capable in all modes of operation that you will get musically usable, pro sounding results no matter which outputs you use. Let us spend less time quibbling over theoretical differences in sound quality and undetectable additional A/D to D/A conversions and more time making music. That is, after all, what draws us together as a community to have these discussions in the first place.
I will hold off posting the results until I get enough responses. I’d like to get at least 1000 responses before posting results so it could take a while. Post on your favorite audio forums and get people involved taking this test. I’d love to have as many perspectives as possible. Spread the word!
|Line 6 POD X3 Live
This is the preamp/modeler used to create the sound clips on this page. One of the sound clips is recorded using the USB drivers of this unit.
This is the soundcard used to record the “other” two samples. One sound clip went through the analogue inputs while the other went to the S/PDIF input. This is a great home studio soundcard with great converters.
|Live Wire S/PDIF
This is the cable I used for the S/PDIF part of the test. S/PDIF comes in a few flavors that include optical. If you are going to be doing some digital recording make sure you get the right cables. The S/PDIF cables with RCA ends are coaxial (coax) while the ones with TOSLINK ends are optical.
I was holding out for 1000 responses and now have the required number of guesses. With a thousand responses there were 1.2% percent of correct answers, and I suspect a few of those were just luck. The correct answers are
- A = analogue signal
- B = digital via S/PDIF
- C = digital via USB
NOTE: There has been some discussion about the 1.2% figure and what would be the likely correct percentage if everyone was truly guessing. There has also been some suggestion that the 1.2% means people hear the difference but it is the opposite of what they expect. I would like to say that I agree with the theory of those conclusions but they are also incorrect. The reason we have such a low (1.2%) of correct guesses is that the many participants did not submit guesses but instead gave up at, “I don’t have a guess, I just can’t tell.” I counted those hundreds of submissions as incorrect.
Could you tell the difference? I hope this has served to illustrate the point that you don’t need to worry so much about ideal signal flow or additional analogue to digital conversions. You’re going to get great results no matter which path you take for your home studio recordings. You will make much better recordings if you focus more on inspiration/creativity than worrying about the ones and zeros. Have fun!