[Jim McC]

When a headphone is plugged into an A/V receiver's headphone jack, is that considered being "amped"? Thanks.

 

[kramer5150]

IMHO yes.  Any time you add a gain stage the signal is being amplified.
Some receivers have very robust and good sounding headphone outputs too.

 

[Jim McC]

Thanks. I noticed when I plugged in 2 cans with a Y-cable the volume was almost in-audible. Is that normally the case with A/V receivers?

 

[PurpleAngel]

  When a headphone is plugged into an A/V receiver's headphone jack, is that considered being "amped"? Thanks.

 
When you plug headphones into a receiver, the amplifiers that were driving the speakers switch over to driving the headphones, so the headphones are "amped".
The headphone output jacks on most receivers has a high impedance, which can induce a bloated (louder, less detail) bass in low Ohm headphones.

 

[cel4145]

When you plug headphones into a receiver, the amplifiers that were driving the speakers switch over to driving the headphones, so the headphones are "amped".
The headphone output jacks on most receivers has a high impedance, which can induce a bloated (louder, less detail) bass in low Ohm headphones.

Agreed.

And when you use a y splitter to connect two pairs of the headphones, the resulting impedance load will be different than the headphones individually because you are hooking them in parallel:
http://www.sengpielaudio.com/calculator-paralresist.htm
Could be you are ending up with a very low impedance load that the headphone amp is just not well-suited to drive. For example, if you hook up two 32 ohm headphones to the headphone amp, the amp will see that as a 16 ohm load.

Next, unless the two headphones are the same exact make and model, good chance they have different sensitivity levels, which means that they will not achieve the same volume with the same amount of power split between them.

 

[Jim McC]

Thanks