|However...Tim, I'm intrigued by the Panasonic receiver. Is it really that good with HPs? Digital receivers have certain inherent advantages, like tidy digital connections and the ability to adjust volume via remote in much finer increments. How long has this receiver been out?
I have the SA-XR55, which has been out a few years. I'm not sure you can find one at this point. the XR57 is essentially the same receiver. I can't tell you a whole lot about the headphone amp in it. Only that it is op-amp based. I know this because I wrote to Panasonic and asked. Perhaps the headphone amp benefits from the fact that the signal path, up to the point of conversion, just before amplification, is all digital. Perhaps it benefits from the fact that all of the digital processing is 24 bit (even if you feed it an analog signal, a 24-bit ADC converts it at the front end and all processing, until conversion back to analog just before putting voltage on the speaker terminals is digital and 24-bit). I don't really know. What I know is that it drives my HD580s well, with excellent bass control, very fast transient response and great clarity. Lots of detail. Big "sound stage" for 580s. Crisp, tight, powerful bass. Very transparent upper mids (cymbals, bells, etc. are very realistic).
Now, with all of that said and a nod to the subjectivity of humanity, I keep going back to my old Harman Kardon integrated amp. I'll set the Panasonic up in my office for headphone listening and listen for awhile. There is no doubt in my mind that it is more precise, more transparent. Then after awhile, I find myself switching them out again and really enjoying the warm, smooth character of the old HK.
But if you want to hear the clarity and speed that big Senns are capable of on the cheap, a Panny digital receiver will do the trick. You should be able to find one for <$300. And as a special benefit, it drives speakers really well, too. Yes, it is an AV surround receiver. But if you set it up in stereo mode, it sends two amps (100 watts each into 6 ohms, about 75 int 8) to each speaker. If you set it up in bi-wire mode, it sends two amps to each woofer, one to each tweeter. That's a lot of remarkably clean, fast, grainless power. There are folks out there who have discovered these receivers and are powering high-end B&Ws, even electrostatics with them. It does not sound mid-fi, much less cheap. The caveat is that it does not sound the slightest bit "euphonic" either. Feed a straight digital signal to one of the Pannys and you will have something that is brutally revealing of the limitations of both your recording and your speakers.