Shortly after my recent acquisition of a pair of Philips Fidelio X2HR headphones, I did some reading and found that there is a variable in audio sources called source output impedance, which can affect the sound depending on the load (headphones) you put on them. The ideal is 1/8 or less the impedance of the headphones themselves, or else the bass in particular will lose definition. Given that the Philips Fidelio X2HRs are 30 ohms, and my Sound Blaster Z outputs 22, I decided I needed to give this a test.

To conduct this test, I bought a secondhand Micca OriGen+ headphone amp. It cost me a handful, but at the price I got it, it was the cheapest (well-reviewed) one I could find that had S/PDIF input and an acceptable output impedance (0.5 ohms, advertised). S/PDIF input is important in this case, because it allows me to bypass the Sound Blaster Z‘s DAC and amp and use the OriGen’s 0.5ohm setup, while still retaining the effects processing of Creative’s Sound Core 3D chip. As it happens, the OriGen+ has the same opamp as the SBZ, the NJM4556 (or JRC4556, all sources I find say they’re the same). Both Cirrus Logic DACs, too – CS4392 and CS4398, respectively.

Fortunately, the Sound Blaster Z is designed in such a way that it can send the same audio stream simultaneously through both its 3.5mm jacks and its optical S/PDIF port. This makes testing very easy, as I do not need to adjust settings for every switch. Thus, the OriGen+ output went to one side of a 3.5mm A/B switch, the Z’s headphone output went to the other, and I adjusted the volumes to match. I then proceeded to listen to many different audio sources. Music, games, movies, using the Philips Fidelio X2HRs (30ohm), Audio Technica AD900Xs (38ohm), Rosewill R-Studio E-860 IEMs (18ohm), and my old Sony MDR-SA1000s (70ohm).

The results were astoundingly unextraordinary. I heard absolutely no difference between the two, at any frequency. Switching back and forth between audio sources during playback yielded no change. Even with the 18ohm IEMs, which are below the impedance of the SBZ, it sounded exactly the same as through the OriGen+.

Either:

  • My ears are not good enough to tell the difference,
  • Output impedance doesn’t make a difference,
  • All of these particular headphones are constructed in such a way that high output impedance doesn’t matter,
  • The impedance on the SBZ is much, much lower than 22ohms, the OriGen+ is higher, or all the headphones are much higher.
  • Or an unknown factor is negating the difference.

Don’t get me wrong now; the Micca OriGen+ sounds awesome it its own right on S/PDIF. It’s just not different from the Sound Blaster Z alone. In any case, I no longer feel any need to try to nitpick the output impedance of my¬†Sound Blaster Z. It’s good enough just the way it is. Was discovering this worth the money? Probably not.

Okay, then. Have at you.