Also give me the output of
"sudo lspci -s 8:0 -vvnn"

and

"lsmod | grep snd"

EDIT: Gah, my brain doesn't work sometimes. I assumed you meant the RIVE onboard Realtek codec but you are using a Phoebus. Although I saw the C-Media Electronics Inc Device 5011 I didn't make the connection lol. There is currently no kernel driver module for CMI8888 that the Phoebus uses. As far as I know work is being done so that hda-intel driver will support it. Unless you want to hack into the snd_hda_intel sources yourself your best bet is switching to your onboard sound for now. Do post the output of the above commands though, I want to see if snd_hda_intel is loaded for the device or not.

EDIT2: You could try pulling kernel and alsa packages from rawhide if you are familiar with the process but not sure if that would work due to dependencies.

Thank you for your effort mate.
In this case, I don't think it is worth all the effort on making the Phoebus to work right now...
After all, I still think playing game (Using Phoebus) under Windows is a lot better.

Anyway, please see the output below

08:00.0 Audio device [0403]: C-Media Electronics Inc Device [13f6:5011]
Subsystem: C-Media Electronics Inc Device [13f6:5011]
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- SERR-
Latency: 0, Cache Line Size: 64 bytes
Interrupt: pin A routed to IRQ 11
Region 0: Memory at fb700000 (32-bit, non-prefetchable)
Capabilities: [40] Power Management version 3
Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
Capabilities: [50] MSI: Enable- Count=1/1 Maskable- 64bit+
Address: 0000000000000000 Data: 0000
Capabilities: [70] Express (v1) Endpoint, MSI 01
DevCap: MaxPayload 128 bytes, PhantFunc 0, Latency L0s <128ns, L1 <2us
ExtTag- AttnBtn- AttnInd- PwrInd- RBE+ FLReset-
DevCtl: Report errors: Correctable- Non-Fatal- Fatal- Unsupported-
RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop-
MaxPayload 128 bytes, MaxReadReq 512 bytes
DevSta: CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr- TransPend-
LnkCap: Port #0, Speed 2.5GT/s, Width x1, ASPM L0s L1, Latency L0 <512ns, L1 <64us
ClockPM+ Surprise- LLActRep- BwNot-
LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- Retrain- CommClk+
ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
LnkSta: Speed 2.5GT/s, Width x1, TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt-
Capabilities: [ac] MSI-X: Enable- Count=1 Masked-
Vector table: BAR=0 offset=00000000
PBA: BAR=0 offset=00000000
Capabilities: [100 v1] Advanced Error Reporting
UESta: DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
UEMsk: DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
UESvrt: DLP+ SDES+ TLP- FCP+ CmpltTO- CmpltAbrt- UnxCmplt- RxOF+ MalfTLP+ ECRC- UnsupReq- ACSViol-
CESta: RxErr- BadTLP- BadDLLP+ Rollover- Timeout- NonFatalErr-
CEMsk: RxErr- BadTLP- BadDLLP- Rollover- Timeout- NonFatalErr+
AERCap: First Error Pointer: 00, GenCap- CGenEn- ChkCap- ChkEn-

[hide@hide ~]$ lsmod | grep snd
snd_hda_codec_hdmi 36232 8
snd_hda_intel 37618 0
snd_hda_codec 126889 2 snd_hda_codec_hdmi,snd_hda_intel
snd_hwdep 17650 1 snd_hda_codec
snd_seq 64844 0
snd_seq_device 14136 1 snd_seq
snd_pcm 97459 3 snd_hda_codec_hdmi,snd_hda_codec,snd_hda_intel
snd_page_alloc 18101 2 snd_pcm,snd_hda_intel
snd_timer 28690 2 snd_pcm,snd_seq
snd 79242 8 snd_hwdep,snd_timer,snd_hda_codec_hdmi,snd_pcm,snd_seq,snd_hda_codec,snd_hda_intel,snd_seq_device
soundcore 14491 1 snd

As was expected there's no driver loaded for the card. snd_hda_intel should support it soon (without advanced features) and snd_oxygen should eventually provide support with extra features. For now if you want to try and get it working you can see this thread:
http://www.mentby.com/Group/alsa-user/asus-xonar-phoebus-support.html

but it involves recompiling a kernel 🙂