Q:

Using dvb-t device as rtl-sdr

I am wondering if I can use that dvb-t device to listen 48-836 mhz? 

if it's no, why? 
thanks..

A:

If the specific device is built around the Realtek RTL2832U chip, then the rtl-sdr driver software will be able to use it as an SDR. 
If it uses a different chip, then that driver will not work.  It might still be possible to use that hardware, but would require writing new driver software and possibly reverse-engineering (the same as the original RTL-SDR development project). 
It is also worth noticing that rtl-sdr actually does not use the DVB-T capabilities of the devices it works with at all — the raw-samples mode of the chip is narrow-band compared to what is required to receive DVB-T and was used by the original software to receive FM radio, not video.  Hardware that only has a DVB-T mode cannot be used as a SDR.