Quote:
Originally Posted by
jslade 
No kidding. From what I've read, an amp does more than just boost the volume of the headphones, though, correct?
How are your experiences with the HD 600? I like the look of them, and from everything I've read, they definitely seem like part of the gold standard of sub-$500 headphones.
Sorry, I meant HD-650. I started with the HD-580, then HD-600, and now listen to the 650. There have been incremental improvements over the years, but the character's pretty much the same, which is to say they're pretty mellow and invite you to listen in rather than beat you over the head with their sound. I'd love to try the 800 or 700, but I'm pretty happy with what I have now. I use the 600s at home occasionally, and I'd be happy with them, too. That one I plug into an iPad for listening.
I like how Sennheiser phones, at least in this line, are pretty user serviceable. Over the 18 years I've been using these phones (got the 580 in 1994), I've been able to fix bad cables, tired ear cushions, and even one dead driver (that was caused by my clumsiness) by myself for very reasonable parts cost.
An amp does a bunch of things, but basically it has to make the input signal bigger at the headphones without doing anything else to the signal. This has any number of technical implications, but if the volume is loud enough, there isn't obvious distortion, and the frequency balance seems the same, then it's doing a good job --- you don't hear a good amp in operation.
I have a bunch of headphone amps in a range of prices, but in general, I think the need for them is overstated.