buffered vs. unbuffered outputs?

The unbuffered will sound better if you have short ICs to the amp and a high input impedance amp - 100kohm would be ideal, otherwise, you might prefer the buffered output since you will need buffering to drive the ICs and amp properly. In a well matched system, as I described above, unbuffered will sound better than buffered (to most people).

The unbuffered really allows the source to be the drive to the amp, with only a volume control and perhaps a selector switch in the line. So IF your source can drive the amp like this, then it is the way to go.
IF your source has any difficulty driving the amp. that is it sounds lean, or lacks dynamics, THEN you will need to use the 'buffered output'. The buffer creates a proper impedence match between the source and amp, so the source is NO LONGER what the amp sees as the voltage source. The buffer is now the voltage source. The buffer adds a layer of electronics to the signal.
So if you are in need of using the buffer, well, use it.
Actually just LISTEN to the sound with, and without the buffer, and choose the one that sounds best. The one that sounds best IS the one to use.
Also, you can use the buffered output for a second device, a headphone amp or whatever if you find the non buffered out to the amp is good.
The reverse IS NOT TRUE. do not use the unbuffered out if the connection to the main amp is the buffered one.

My rig uses the Mcaormack DNA-1 deluxe amp and the ICs are only 1/2
meter long. The speakers are Thiel 3.6s I don't know what the amp's impedence is but ear-breaking volume is possible if you want it.

Sounds to me you are saying to use the unbuffered outputs.

I'm interested in the sound being most realistic with no embellishment at all.
Does the buffering issue effect this dimension ?
And thanks for your response.
Ed

Only YOUR ears can tell you.

ELizabeth is right, listening is the way to go, but the amp
impedance is critical, but has little (nothing?) to do with
how loud it will play, the impedance mismatch effects the
frequency spectrum. Your amp has a very high input impedance
for an SS amp (100 kohm) so it should match very well with the
TLC's unbuffered outputs:) Which will sound better to you?
Only you can tell, but with this match up, the unbuffered
outputs should outperform the buffered as it does not seem you
need any buffering to match the impedances and using the
buffers just adds more electronics to muck up the signal -
necessary when you need it, but you shouldn't.

I had the TLC-1 and DNA 0.5 deluxe. To my ears, the passive (unbuffered) output was decisively superior. Like Pubul57 said, the input impedance of your amp can easily handle a passive. In fact, I believe Steve McCormack designed it that way.

All your replys were very helpful to me. I've started listening with "new Ears"
and I think you are all correct! Unbuffered sounds more realistic and un-embellished to my ears now that I've taken the trouble to compare really carefully. Thanks again everyone.
Ed