hi all i am looking into buying either a HD595 or HD558 and just wondering if either would benefit from a amp
i was looking into buying a Nuforce Icon U-dac 2
I believe they definitely benefit from an amp. Having owned the HD598, I found it to sound pretty weak without an amp. Once I introduced the E9 to the HD598, the headphone came to life for me. In comparison, I found that at least volume wise, it needed as much power as the K701 I owned. Just amping is more about volume, but I found the HD598 to nearly as much. I'd definitely look into some juice for the HD598. Not sure on the UDAC2 as an 'amp' though.
Assuming my HD598 is similar to HD558/HD595, look for a decent amp AND a decent DAC.
Going from Nuforce UDAC 2 to AMB's Gamma 2 DAC was a huge improvement to my HD598 rig, the kind one notices after 10 seconds of listening.
The U-Dac 2 should more than suffice when driving Sennheiser's HD5-series as they are very efficient and relatively easy to drive. I personally have used Fiio's E5 with the HD515 with some suprising results, so the U-Dac 2 should work for you.