beyer 880/600 amp

Really low cost single tube headphone amplifiers, sold on eBay, ships from China, takes ten days.

Prices start out at $45, better ones start at around $75

Usually need a digital multi-meter (DT830) prices start at $7.

Use the multi-meter to do fine adjustments to the voltage for best sound.

They every easily drive my 250-Ohm headphones.

and usually the single tube headphone amplifiers are rated up to 600-ohms.

I think Indeed is a good brand sold on eBay.

Go to the RockGrotto website forum, they like tinkering with these kind of headphone amplifiers.

Might even be a few threads here on Head-Fi.

I also have a 880/600 on it's way.

Just wondering if something like the iBasso P4 would be strong enough?

Solid State Amps...

JDSLabs C421 does a good job with them...

another one that works well is the O2 head phone amp... you can build your own or get

one already built...   set the gain for 10x or 12x

of the two the C421 is the more portable one... also has a bass boost if you need it..

Most anything can drive 600 ohms reasonably well.  If you like the sound signature or lack of sound signature of the amp, it's probably going to match well, unless maybe you're looking at something that intentionally boosts the treble even more.

It's just that most cheaper amps don't have the voltage swing and power to drive them loud.  For around 110 dB SPL, you need about 43 mW (into 600 ohms), or equivalently around 5.14 V rms output, according to measurements at InnerFidelity.  With more dynamic range compressed music, I doubt anybody will want to listen that loud with peaks at 110 dB, so in that case the requirements are not as steep.

JDSLabs C421 looks just a couple dB not powerful enough for that, considering the supply rails are +-7V and the output op amp is not rail-to-rail.  (I missed seeing an actual spec, so I'm just going by those considerations.)  For most people and most music that's plenty fine though.

On quick inspection I don't see much info on the iBasso P4 either, but claimed 600 mW into 32 ohms implies 4.38V rms into that load.  If that figure is current limited, then into 600 ohms the max output will be higher, and that's probably enough.  If not, or if they're being "optimistic" on their specs, then that's probably a little short as well, which again may still be well okay.