Noise from "silent" PC, Trying to fix it!
Noise from "silent" PC, Trying to fix it!
Oct 15 2012, 16:25
Joined: 24-July 07
Member No.: 45592
Thecus N5200B NAS - ethernet cable - silent PC - firewire cable - Weiss DAC2 - Nordost Red Dawn XLR cables - Classe CAP2100 - Atlas speaker cable - B&W 804s (with Soundocity Outrigger)
Known as the "CAPS version 2" - a custom PC build designed by Chris Connaker of the Computer Audiophile website (www.computeraudiophile.com). Mine was built by Small Green Computer who have linked in with Chris Connaker (http://shop.smallgreencomputer.com/CAPS-20-CAPS.htm).
Origen ae M10 case; Jetway NF96FL-525-LF motherboard; dual core 1.8 GHz Intel Atom D525 processor; 2x2GB modules of DDR2 667 from Transcend; 64GB Micro Center SSD drive; SOtM In-Line SATA Power Noise Filter; SYBA SD-VIA-FW1E1H PCI FireWire card (6-pin); Casetronic PW-12V5A-L5 60w power supply. More details about the CAPSv2 available here: http://www.computeraudiophile.com/content/...erver-caps-v20/. It is running Windows 7 Ultimate service pack 1 64-bit.
The PC, supposedly silent, emits a noise. The noise can be divided into 2 components; a constant "crackling" noise - this is quiet though audible with the ear near to the case. It seems to fluctuate if the PC is being used (e.g. scrolling down through a website or starting a program). Moving the mouse causes slight fluctuations in it. The second noise is the main problem - a constant high-pitched emission; this noise starts when the firewire port is connected to an external device.
The noise only starts when Windows boots up to the main screen (it is not there on the BIOS screens). The noise is definitely coming from the PC unit itself and not anything external to it such as the speakers. Given the effect the firewire cable has on the noise, I ran some tests:
1. All equipment off & connected - no noise
2. Monitor on - no noise
3. CAPS on - no noise initially, then system beep, then some noise when the Windows logo appears, then the continuous noise when the Windows welcome screen and then desktop appear
4. Unplug monitor from CAPS - 1 second pause in noise, then resumes
5. Switch on DAC (connected to CAPS via 6pin-6pin firewire cable) - 1 second pause in noise, then resumes
6. Switch off DAC - noise continues, no pause
7. Unplug power from DAC - noise stops
8. Plug in power to DAC - 4 second pause, then noise resumes
9. Unplug firewire cable from CAPS - noise stops
10. Plug in firewire cable to CAPS - 2 second pause, then noise resumes
11. Unplug firewire cable from DAC - noise stops
12. Plug in firewire cable to DAC - 2 second pause, then noise resumes
13. Unplug/plug in ethernet cable to CAPS - no change
14. CAPS off - noise stops
I have opened up the unit to take a look inside. It's not really possible to isolate where the noise is coming from; the red circle in the photo below given my best guess but it could be wrong:
I tried disconnecting the SSD and booting up; I get a message saying "reboot and select proper boot device". There is no noise, though the noise only starts when the PC fires up into Windows anyway.
I looked into the firewire drivers on the PC. I tried a few different drivers that came with Windows, though they did not alter the sound. I then tried a driver from a third party (Unibrain - ubCore Firewire (Firewire 800 - IEEE 1394b) driver suite) and this significantly reduced the noise. However, when this driver was selected, the driver for my Weiss DAC2 seems to stop working:
The DAC2 is not recognised as long as the Unibrain firewire driver is being used. If I select the Windows legacy firewire driver and then disable the DAC2 driver, most of the sound goes away also (though not all of it). Of course I then cannot play music through the system as the DAC is disabled. I have tried a different firewire cable (4pin to 6pin) and used a 4pin to 6pin converter; this should cut the power leg of the cable. However, again no difference in sound.
When I run the Weiss DAC2 controller info program, it detects the OH 1394 Host Controller as: (1106) VIA Technologies, with chipset (3044) VT6307/6308. Finally, I tried connecting 2 firewire cables concurrently (there are 2 ports on both the DAC and the PC). This reduced the noise, though music will not play on the PC.
As you can see I have struggled with this for a while - any suggestions greatly appreciated!
This post has been edited by extracampine: Oct 15 2012, 16:39
Oct 16 2012, 20:42
Joined: 16-February 03
Member No.: 5032
An ATX power supply is what most non-laptop computers use for power. It takes AC input and supplies several voltages that computers need; +12V, +5V, +3.3V and -12V. They connect to the motherboard using a standard 20 or 24 pin connector along with usually a dedicated 4 or 8 pin connector for the CPU. A good quality one can have very good regulation with very stable output. Even with these multiple voltages, all modern motherboards have DC-DC converters for supplying other voltages that things like the CPU need.
A "brick" in this context is an external power supply that usually supplies only one voltage, +12V. The rest of the voltages must be generated from the +12V, in your case your motherboard does it with extra DC-DC converters in addition to the ones normal motherboards have. My hypothesis in regards to your problem is that those extra DC-DC converters on your motherboard are causing the noise and are of lower quality then found in a good ATX power supply.
A "pico-PSU" is a special DC-DC converter that takes the +12V from a brick instead of AC and then generates the rest of the voltages that a normal ATX power supply would create. It is basically the same as the extra DC-DC converters your motherboard has, but designed to plug into normal motherboards that lack them. They are hopefully of somewhat better quality, I have a couple and they make no noise that I can detect.
Your motherboard is different then most and expects only +12V from a brick. It in fact cannot use a normal ATX power supply (without some hacking) or a pico-PSU. It does not have the connectors needed to hook up a normal computer power supply. My comment about the pico-PSU was for use with a replacement motherboard that has the normal connectors. You could use any normal ATX power supply with a normal motherboard, but your small case limits the size so a pico-PSU would fit.
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