[Dogbane]

How does the impedance of headphones affect the choice of amp?
Would one choose a different make/model (in a given price range) for low impedance phones than for high impedance? Are tubes better with one and SS with the other?

 

[tintin47]

With broad strokes: Ideally, you want the output impedance of the amp to match the nominal impedance of the headphone. If that isn't possible, then you want the output Z lower than the headphone Z. Cheap tube amps are built output transformerless (OTL) because good transformers cost a lot. OTL tube amps have high output impedances, so you should generally avoid pairing them with a low Z phone. SS amps generally all have output impedances near 0, so they work well with pretty much any phone.

There is a lot out there on the subject. You can google some of the stuff I mentioned and learn a lot if you so desire.