[muad]

So I recently decided to downgrade my setup to free up some cash. Previously I was using a HD650 with the o2odac combo. I picked up a set of hd558 and a xonar dg to replace it. So here is what I did...
 
I fist removed the foam from the hd558. This significantly improved the airiness and noticeably improved the imaging. I assume the foam was leading to some reflections and was muddying things up a little. Needless to say I was thoroughly impressed with these cans. I found I was enjoying it far more than I ever enjoyed my HD650s, everything was clean, clear, with a definite space around sound stage elements in many recordings. I could pinpoint exactly where everything was in a 3d space, there was well defined depth, height and width separation. I was amazed! This was all out of the xonar dg, which was set to hifi mode to bypass the DSPs.
 
Next, curiosity hit me and I tried my hd650s again with the o2odac, and the sound stage was closed in and fuzzy. Instrument separation was difficult to distinguish. It sounded like **** but that beautiful tone was still intact. I assume that is just they way they are. When I tried my hd558 out of the o2odac they didn't sound the same as before. The separation and imaging was still better than the hd650s but not as clean and crisp as out the xonar dg. I tried it at varying volumes and no improvement. Normally I can't tell the difference between an amp and plugging my headphones into a light socket, but there is an obvious difference here. So I am trying to understand what has happened here. Based on the measurements the o2odac is theoretically perfect relative to human listening ability. So either two things happened:
 
1. The o2odac is broken
2. The xonar dg is accentuating certain frequencies and creating the illusion of clarity and improved imaging?
 
I posted this in the sound science forum because I figure I would get a straight answer or at least theories here, instead of the ******** and amp recommendations that I would be showered with anywhere else.
 
Thank you for taking the time to read this.  

 

[mikeaj]

Here are some things to try, look into, and think about. If you have questions about any of these, ask:
 
1. level matching all comparisons so same exact volume (I would use multimeter and/or splitters to facilitate measurements and a constant tone like you can find somewhere or generate in say sinegen or Audacity). also, when switching amps and sources, avoid taking headphones on and off, just to be a little more consistent about headphone placement-related impact on sound
 
2. what are the gains on the O2? anyway, use low gain just to be sure
 
3. other stuff aside that some people will contest and others won't, on some IEMs the O2 coloration due to (~0.5 ohms) output impedance could be ABXable I think in ideal conditions and the volume matching at lower volumes is also not audibly perfect... but this is not really relevant here so just a side comment
 
4. what's the output imepdance of the DG? you can determine this yourself by measuring the output voltage level with two different loads and solving the trivial systems of (two) equations
 
5. try comparing DG to DG -> O2 with the O2 volume turned such that you're getting the same volume both ways
 
6. try blind test (find a helper to connect a setup behind your back and have you guess which you're listening to) to see if your results still hold

 

[bigshot]

Don't laugh, but ear wax can be a cause of this sort of thing too. I had a pair of closed cans that made my ears sweat and the sound changed.