hooking up 4 headphone amps to 1 line output?

I've built 4 headphone amps, which I need to hook up to a balanced line output.

I'm going for a simple opamp based balanced-to-unbalanced converter, that will feed all 4 amps. Its the (a) version:

The questions is, do I need to buffer the line signal? The headphone amps have 1Mohm impedance/amp, and the line "sees" all 4 amps/impedances=250kohm
...or does the balanced-to-unbalanced converter work like a buffer?
If I need a buffer, should it come before or after the bal-to-unbal-converter?

Hi Chrion,
I have also built a 4 headphone amp. I have connected all togather in parrallel. These are working fine.

dinesh: Cool. But if you don't use a buffer, doesn't the volume suffer from the line signal been "split" into 4 signals?

To make things easier, can I just short pin 1 and 2 on the xlr and skip the opamp based balanced->unbalanced circuit?

Hi Chrion,
I never got any problem, whether I drive 1 or 4 headphones. If you are looking for balanced input then try this Schematics.

http://www.forsselltech.com/schematics/BalOut1.pdf

To make things easier, can I just short pin 1 and 2 on the xlr and skip the opamp based balanced->unbalanced circuit?

Click to expand...

I think you must Check the Manual of your Equipment with which you are going to connect your headphone amp. Mostly all professional equipments support balanced & unbalanced connection on same output sockets.