Sennheiser HD650 and ipod

A good headphone amp should only help, not hurt.

Glad to hear they sound good as is though as well.

I have Sennheiser Momentum over-ear phones. THese are designed to work better with portable devices than the audiophile Sennheiser models like HD650, and sound wonderful of an Ipod TOuch, for example, but I think even these can benefit from a good amp with a bit more juice than most common portable devices can deliver.

Ditto what Neal said above.

I've been using my 10yr old HD600's more than ever since I picked up a Fiio E12 + L9 cable (for under $140!). I use it with my 160 GB iPod classic that has close to 6000 songs on it. The cable bypasses the pods amp resulting in a very clean and powerful sound. The amp also has a 1-click subtle but effective bass boosting switch that I always leave on. This little amp is slightly larger than my phone. This is why, between the portability, song selection, and sound quality, I've been using my cans more than ever!

Has anyone tried the ifi nano ican portable? They claim a 70 hour use on one charge...

Sennheiser HD580/600/650 got a rep as hard to drive cans, but they're really not that bad. They're highly efficient (for full-sized open cans), which is good. Then there's the 300-ohms, which is both good (presents an easy load; doesn't demand a lot of current) and bad (your source+headamp must have enough net gain to get where you want to go volume-wise). On the other hand, something like a Grado won't require as much voltage to go loud (because their lower impedance actually drws more current & power form the amp at the same volume), if you can stomach their sound :)

The other reason they got that rep is that they do "scale" their performance with higher-end upstream gear. However, that's more a relic of earlier head-fi days when there were few other high-end headphone options besides Stax. These days, the HD600 series still represents a GREAT value, but they have a low (compared to the best) and hard glass ceiling on their performance, so it's not worth dumping much money into a dedicated HD600/650 system before you should explore other options.