[William Sommerwerck]

It's important to do a little research to choose the right box to
purchase,
and you point out some of the important parameters, but most off-the-shelf
adjustable devices intended to do the job have enough attenuation range
and reasonable input and output impedance for a line level application so
that it's hard to make a mistake and choose the wrong one. It's really
more
important to make sure the right connectors are available than to
worry about whether it's balanced or unbalanced, or 5K or 20K input
impedance.

This is good advice. But the OP said he wanted to DIH.

He should be able to find an off-the-shelf attenuator that will let him do
what the wants.


This is stuff you need to understand to improve your engineering skills.
I urge you to get some literature on basic design and study it.

It sounds like we're not dealing with a would-be engineer here, just
someone
who wants to get a job done. He would be better served simply by calling a
dealer, describing what he has, what he needs to do, and asking what they
sell that will fix him up. But a lot of people tend to mistrust dealers.
That only means you're going to the wrong dealer.

It doesn't hurt to have the basic technical knowledge needed to deal wisely
when making a purchase.