Is there a way to adjust the volume of headphones separately from adjusting the volume on the audio/video receiver?

I do that with Sennheiser wireless headphones taking their input from the cable box and turn the TV up and down independently from the headphones.

Some headphones, and all earbud sets, have a separate volume control built into the chord. there are likely auxiliary volume controls, like those for remote speakers, available for earphones, if you look for them. Separate earphone amps are another, though usually expensive answer too, though these are meant to be upgrades for hi fi gear aficionados. Having both audio room output and earphone output on a receiver that is not wired for that might require a work around such as looking for an adapter for a low level output pair on the amp rear, or running an input splitter and/or, as mentioned, unfortunately a separate earphone amplifier. If your system shuts off speaker output when you plug in the earphones, and offers no setup option, you are pretty screwed, and will have to money the problem.

A easy way around this is to buy a simple headphone amp and connect it to the TAPE OUTPUT rca jacks on the back of the receiver. Tape outputs to headphone amp inputs - headphone output to headphones. The tape output will put out a constant volume so you will need to place the amp near where you sit so you can adjust the volume. This may mean that you will need to buy a really long red/white RCA cable pair.

This will work:

https://www.amazon.com/Technical-Pro-MA2020-Amplif...

https://www.amazon.com/AmazonBasics-2-Male-RCA-Aud...

No, not directly.

As others say, you cannot do anything like that with the existing amp, or most general amps.

The simplest solution is get a separate headphone amp that takes a line level input and connect that to an auxiliary output of your existing amp - a "preamp out", "record out" etc., something that has the low level signal.

Most of the headphone amps on ebay are either expensive gimmicks or rechargeable battery units for portable gear.

This style is not perfect, but quite cheap and should work, but it depends on the input level:

https://www.ebay.co.uk/itm/HA400-Ultra-compact-4-C...

This is the only other straightforward externally powered amp I've been able to find so far; more expensive but higher powered and likely rather more gain:

https://www.ebay.co.uk/itm/LAmini-Headphone-Amplif...

You need a separate headphone amplifier.

>> There are a VERY few receivers and amplifiers

that have separate headphone sections built into them.

I want you to fully understand that they are SO few and far between

that seeking them is a virtually useless exercise.

Most receivers work on the basis that a plugged in set of headphones mutes the output to the speakers. The reason for this is basic: Most people who use headphones do so because they wish to use headphones so that the sound from the speakers does not disturb other people in the house.

Can your wife listen to the TV's audio while you use the headphones ?

If there is a left right control adjustment .