Snapcast - Server Configuration failed message - partly solved

Hi, I installed Snapcast Plugin according to Saiyatos Quick start guide. It is basically running, means Arduino and Windows clients can connect. But sound played on Volumio is not transferred to tmp/snapfifo, at least no sound at any client.
When I try to change configuration on plugin site of Volumio hompage at Snapserver Settings or Patch ALSA configuration file I get this error message:

Configuration failed, Failed to update asound configuration with error:Error: Command failed: /bin/sed -i – ‘/#SNAPCAST/,/#ENDOFSNAPCAST/d’ /etc/asound.conf /bin/sed: couldn’t open temporary file /etc/sedTVYuVO: Permission denied

I tried to change location of asound.conf to /home/volumio/ but due to same error message no chnage happens.

See you,

I made a fresh install of Volumio on my Raspberry 2 and additionally only the Snapcast Plugin. The Connection of Clients works and now I have sound. The error message still exists and the sound on all clients is very poor, sounds like over compressed or very low transfer rate.
Server-Plugin on Volumio 2.5.1
WinClient Snap.Net reports: Version 0.25.0, Server version is 0.15.0
Android Snapcast
I could modify asound.conf via SSH but I fear I make it worse. I wonder on format “raw”. Is this right or the result of the failed modification from UI menu?

    pcm.!snapcast {
            type plug
            slave.pcm snapConverter

    pcm.snapConverter {
            type rate
            slave {
                    pcm writeFile # Direct to the plugin which will write to a file
                    format S16_LE
                    rate 48000

    pcm.writeFile {
            type file
            slave.pcm null
            file "/tmp/snapfifo"
            format "raw"

I found the reason for the strange sound. In MPD.conf the sampling rate was 44100 and mixer_type was missing.

MPD.conf part

audio_output {
    type            "fifo"
    enabled         "yes"
    name            "multiroom"
    path            "/tmp/snapfifo"
    format          "48000:16:2"
    mixer_type      "software"

Still no clue how to solve the asound.conf error message but now it works aat least.

Regards, Holger