Your system information

• version: Stable + Beta
• Distribution: Arch*
• beta?: y
• system updates?: Multiple times daily.

issue :

Because on my system using steam's libs resulted in more issues than I'd like to list, I'm using native libs. (STEAM_RUNTIME=0) Steam refuses to load at all with its libs.
As described in (closed) issue #2066, PTT in the steam client does not work. Setting to PTT results in a still open mic. Microphone input volume slider also does nothing. My system is pure ALSA though this issue also exsisted when using Pulse in a XFCE4 setup. I also use a DMIX setup as is required for a functional system.

Games such as Dota2 and CS:GO have functional PTT. This only affects client voice chat.

reproducing:

1. Run steam
2. Set voice options to push-to-talk
3. Not profit.

$ cat /proc/asound/cards
 0 [D1             ]: AV200 - Xonar D1                        <--- Output
                      Asus Virtuoso 100 at 0xd000, irq 17
 1 [Device         ]: USB-Audio - C-Media USB Audio Device    <--- Input
                      C-Media USB Audio Device at usb-0000:03:00.0-1.2, full speed

$ arecord -l
**** List of CAPTURE Hardware Devices ****
card 0: D1 [Xonar D1], device 0: Multichannel [Multichannel]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: D1 [Xonar D1], device 1: Digital [Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: Device [C-Media USB Audio Device], device 0: USB Audio [USB Audio] <---- Device in use
  Subdevices: 1/1
  Subdevice #0: subdevice #0

  $ lspci | grep -i audio
01:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Tahiti XT HDMI Audio [Radeon HD 7970 Series] *Blacklisted*
05:00.0 Multimedia audio controller: C-Media Electronics Inc CMI8788 [Oxygen HD Audio] *This is my Asus Xonar card, not usb mic*