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 [Solved] Audio server and (CPU ?) noise 
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Joined: Thu Oct 17, 2013 1:06 pm
Posts: 26
Post [Solved] Audio server and (CPU ?) noise
I'm running a fit-PC3 low power (2x2Gb-T40E-WB-FM4U, RTL8188CE 802.11b/g/n WiFi Adapter (rev 01) network controller) as a headless audio server with a M2TECH Hiface USB 384/32 DAC (http://www.m2tech.biz/hiface_dac.html) and a 256GB Samsung 840 Pro SSD hard disk.

The operating system is a minimal Debian stable (Wheezy) base system with a ssh server, mpd (Music Player Deamon) and AssetUPnP server. Installation of Debian Wheezy ran out of the box modulo two remarks:

1) the kernel module for the network controller, rtl8192ce, has to be loaded with the options "ips=0 swlps=0 fwlps=0" to prevent the controller from powering down (and, therefore, make the fit-PC3 unreachable via ssh) after a few hours of operation. This can be achieved by adding a file "rtl8192ce.conf" to "/etc/modprobe.d" with the single line:

Code:
options rtl8192ce ips=0 swlps=0 fwlps=0

2) In "/etc/modprobe.d/alsa-base.conf" the line

Code:
options snd-usb-audio index=-2

has to be replaced by

Code:
options snd-usb-audio index=2

to ensure that the DAC is always associated to "/proc/asound/card2/". This is useful for configuring mpd and seems to avoid the issue reported at http://forums.debian.net/viewtopic.php?f=5&t=109929.

After 3 days of operation I can say that I am very pleased with the fit-PC3 as an audio server. It runs very reliably and built quality is excellent. Under normal operation, the CPU load is betweem 1% and 5% and memory usage is less than 1%. Both cores are running at 800 MHz and the reported temperatures are:

Code:
nicola@fitpc3:/etc/modprobe.d$ sensors
acpitz-virtual-0
Adapter: Virtual device
temp1:        +52.5°C  (crit = +115.0°C)

radeon-pci-0008
Adapter: PCI adapter
temp1:        +52.0°C 

k10temp-pci-00c3
Adapter: PCI adapter
temp1:        +52.5°C  (high = +70.0°C)
                       (crit = +100.0°C, hyst = +97.0°C)

There is, however, one disturbing problem: in spite of having no fan, the fit-PC3 is not noiseless. Within moderate distance (up to about 2 meters, depending on the listener's sensitivity) and in a quiet environment one can hear a distinct high frequency ticking and a weak high tone whining.

I can hear the noise very distinctly by putting my ear on the fit-PC3 and at distiances up to about 70 cm. My wife hears it at distances well beyond 200 cm.

The noise certainly does not come from the SSD hard disk (I have tested this outside the fit-PC3) or from the USB DAC. It comes directly from the fit-PC3 but I cannot say whether it comes from the CPU or from some other component.

My question is: is there a way to shut down unused components (GPU ?) and possibly reduce the noise level ?

Thanks for your attention,
nbpf


Wed Dec 25, 2013 8:33 pm
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Joined: Thu Oct 17, 2013 1:06 pm
Posts: 26
Post Re: [Solved] Audio server and (CPU ?) noise
Please, see viewtopic.php?f=76&t=5215


Sat Dec 28, 2013 4:55 pm
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