Im using a tl-072 for amplifying audio signal. In inverting configuration like the schematic i've attached.
But feeding vcc/2 = 4.5v in positive pin I get the signal cutted in the upper part as you can see in the oscilloscope screenshot.
So I tryed to feed less voltage there to lower the amplifyed signal and if I feed it with 1.6, the output is centered.
Is that normal? Maybe the input is already offset for some reason? Is this good practice?
Thanks!
Well, if Vcc is 4.5v then Vcc/2 is 2.25V
If it works with 1.6V then it works. ¡No hay problema!
I'm not sure if I trust your "soundcard oscilloscope". 
I assume the green is the input and the red is the output? There's a good chance you are clipping your soundcard's ADC. The line input will usually clip at about 1V, and the mic input will clip at a much lower voltage.
You need one more capacitor at the output to filter the DC bias out of your audio signal.
Do you have a voltmeter? If so, check the DC output with no signal. It should be the same as your VCC/2 reference.
Connect the capacitor-side of R1 to ground. Since it's an inverting amplifier (with a gain greater than one, I assume) That should drive the output to the maximum positive voltage (something less than 9V).
Connect the same point to +9V and that output should go as close to ground as the op-amp is capable.
If you want to do further DC tests and test the gain of the amp you can use a pot connected to the 9V power supply (perhaps with an additional voltage divider depending of the gain of your amplifier.)
Or, since it's an audio amplifier.... Just listen to the audio to see if it's distorted! ...I've built lots of audio amplifiers and I don't own a 'scope. Usually, they work very well or they work very badly.
TL072 is not going to work from a 9V supply.... You need a rail-to-rail opamp ideally.
TL072 is not a single supply op amp (AFAIK).
Try an LT1215
Not all opamps have symetrical clipping, so if you want the max swing from the output, you could adjust the midpoint.
Measure with a load attached to the opamp.
I doubt you will get more than 5volt t/t from that opamp with a 10k load, but that migh be ok for audio.
Leo..