Originally Posted by barihunk
My O2 at 1V RMS input and 4x gain is already very loud for me; how loud do you listen to your music usually? Don't want to be preachy BUT do take care of your hearing... once those inner ear hair cells are damaged, they do not regenerate.
But if you really want to hook it up to speaker amps AFAIK you do it like you would speakers, to the output terminals of the speaker amp. Some IIRC use a speaker wire to XLR/TRS/TRRS adapter to plug the 1/4 or XLR cable to the speaker terminals.
When trying the HE500 with C5D vol was turned to max on low gain with noticeable distortion. High gain produced aggravating distortion even at low volumes. The amp was unusable with those headphones.
When trying O2 it was the same except vol level went higher without distortion. I had to go to the max on low gain (6.5x produced distortion much earlier at same volume level). At this point I thought something was broken. A different thing happened when using AV receiver. The distortion was gone but the sound was cloudy and dull like.
I was able to try a headphone amp rated 4W at 50ohm and every note was full with the dial in 10-12 position - enjoyable level to discern the clarity of music and hear all the notes. There was no clipping.
My volume level isn't drastically high. Even at lower vol when specific low or high notes play there is a bottoming out sound or a faint crackle "shooshing" type sound. Lesser headphones like ad900x get louder using O2 yet continue to sound full with no clipping or distortion even at higher than usual vol. Those headphones I believe would be considered "easy to drive." After having tried the HE500 I don't think it is as easy to drive as I've read, at least not to receive the full quality of their sound. I can plug it into an iPod but it doesn't sound as good as inferior headphones coming from the same iPod. Pairing it with the correct amp widens the gap greatly in 500's favor.
My three biggest impressions of the HE500 are that they're very revealing, linear, and the most uncomfortable thing I ever put on my head.
People stated a few times the volume has to be louder on the 560 than 500 so I'm looking at the NFB amps headfiers keep mentioning, especially the NFB15 & 11 (the cheapest ones). I found a few threads with folks using speaker amps to power HE6 & HE500 so I will try it. Hopefully my head won't explode.