> what´s the simplest and best way to distribute the line-in to for example three stereo outs?
That TL074 datasheet is selling op-amps. Unless you expect "many" of your outputs to be shorted, you do NOT need individual drivers for each output. Even if you expect shorts and odd loads, you really do not need multiple drivers.
My first repair task at a radio station, {mumble} years ago, was a Distribution Amp, 24 outputs, each one supposed to be loaded in 600Ω but could be connected to any dang thing (accidents happen). No matter what, "good" outputs "must not" be affected by shorted outputs. It had just one boosted op-amp to drive all the loads.
You build a low impedance amplifier, then put a bunch of resistors on the output:
[IMGDEAD]http://music-club.rutgers.edu/headfonz/DistAmp.jpg[/IMGDEAD]
The buffer amp needs to have an output impedance MUCH lower than the build-out resistors. Ordinary op-amp chips have Z(out) under 1Ω over most of the audio band.
The value of the build-out resistors should be much higher than the buffer output impedance but much lower than the load impedance (or equal to the system impedance for older matched systems, but these are obsolete). If you are fussy about levels, make the build-out resistors 10 times smaller than the load impedances for 1dB loss, which is usually negligible.
However they should be larger than the amplifier's minimum load impedance. If you used 10Ω resistors, and some idiot plugged in a shorted cable, the poor TL074 would distort like mad trying to drive a 10 ohm load. However, a speaker amp would be fine with that.
In my work, I assume hi-fi type loads are 10KΩ and that less than 1dB loss is nice, and I sometimes drive long lines, so I use 470Ω. But in general hi-fi work, 1K or even 2.2K is fine. The TLO74 will comfortably drive one shorted line behind a 470Ω build-out resistor, and maybe two shorts at 2VRMS without distress. I have a dozen outputs, and a professional better than me says "assume 1/3rd of lines may get shorted". So my distribution amp has to drive 470/4= 120 ohms, and needs to be somewhat stronger than a single TLO7x chip. (I also have several shortable 150Ω runs so my buffer is beefy.)
For stereo, you only need 2 op-amps, so a TL072 is plenty for any reasonable number of output, if you do not have to be very concerned about multiple shorted loads.