Setting USB Sound Card to default device

Question

I have been using raspberry pi 3 model B. And, I have installed raspbian jessie with pixel.

I made work its camera without an error. I have bought USB sound Card. But, I couldn't make it to work. My /etc/modprobe.d/alsa-base.conf file

options snd-usb-audio index=0
options snd_bcm2835 index=1
options snd slots=snd-usb-audio,snd-bcm2835

It is insisting to use HDMI audio output. raspi-conf didn't help me. Also I can hear with

aplay -D plughw:0,0 /usr/share/sounds/alsa/Front_Center.wav

My aplay -l output

**** List of PLAYBACK Hardware Devices ****
card 0: Device [USB PnP Sound Device], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: ALSA [bcm2835 ALSA], device 0: bcm2835 ALSA [bcm2835 ALSA]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 1: ALSA [bcm2835 ALSA], device 1: bcm2835 ALSA [bcm2835 IEC958/HDMI]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

and I have edited /etc/asound.conf file as this

npcm.!default {

type hw
card 0 

} ctl.!default{

type hw
card 0 

}

But nothing changed. It is forcing to use HDMI audio output. How can I configure alsa to usb sound card as default.