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Old 30th January 2009, 12:03 AM   #1
HaLo6 is offline HaLo6  United States
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Question PC for a source. Help lowering PS noise.

I am using a PC for a source. However along with its many benefits it has some faults.
One of those being power supply noise which is appearent as noise floor through my speakers. Has anyone come up with a filter of some sorts?

Right now I am using an Antek NSK 2480, which is divided into chambers. I am using a PC Power and Cooling 350 Watt PS. I went with a smaller PS so I could load the PS a little more. When the CPU is being used you can audibly hear a difference in noise floor through the speakers. I am using a M-Audio Audiophile 192 analog out to a pair of PrimaLuna tube amps. I made custom RCA cables that are sheilded. I am also using a SSD as the only drive as well.

The PC is plugged into a Panamax 5100PM which intially helped reduce noise floor, but some is still audible.

Any sugeestions? I plan on switching to USB I2S here soon to see if that helps.
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Old 30th January 2009, 03:16 AM   #2
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Give this a read and see if it helps, as I recall there is a section on power supplies.

http://imageevent.com/cics/v03theart...gcomputertrnsp

Also look at what Peter Daniel is doing here:

"The output from a DAC used with Shigaclone is too low. Besides, I got seriously interested in PC as a source and I like to continue my research. There was discussion in other thread on that subject: "

http://www.diyaudio.com/forums/show...863#post1689863

He is using a pico power supply which is quite interesting. Do a google search on pico PS and you will find what he is doing
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Old 30th January 2009, 09:14 PM   #3
HaLo6 is offline HaLo6  United States
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thanks! Am I far off base in thinking the digital USB should better less prone to PS noise than the PCI Sound card?
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Old 31st January 2009, 03:13 AM   #4
sangram is offline sangram  India
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Nice case, I run my music rig out of one too, and I use the Antec EarthWatts low-ripple 380 watt supply that comes with the case.

I was running the analog output of a Emu1212m straight to my amp and speakers, and now the Emu is only serving for coax output to a Buffalo DAC which in turn feeds the amp.

Noise floor improvements, in my case, have only come from the better Buffalo DAC.

I would suggest you start with power supply and motherboard that is suitable for audio. I can recommend Corsair VX450 or Antec Earthwatts 380 as a starting point, both are super low-ripple. Also ripple increases as the load increases, so a higher rated power supply is a slightly better bet. PCP&C aren't known for low ripple.

For the motherboard, I like Intel original boards because they implement separate power regulation for the PCI slots. Some other manufacturers do, but it is not very clear who. My Asus M2A-VM does not have the necessary power regulators, but since the power supply ripple is supposed to be low (reviews) I do not have a problem with noise while the CPU is used. The difference is of course noticeable when I listen to some recordings at high volume, where the Buffalo sounds noticeably cleaner. Again, that is a difference of the DAC itself, IMO.

Finally, I severely modded the analog stage of the 1212m, with new opamps, caps and voltage regulators for the DAC. Panasonic FM for bypass and decoupling, Black Gate NX in signal path. The improvements were not subtle.

The best way to get the audio out of the PC would either be Firewire or custom USB solutions (not Plug and Play like PCM27xx series).
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Old 31st January 2009, 07:16 PM   #5
HaLo6 is offline HaLo6  United States
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I have the original Antec that came with the case and it was worse in noise floor than the PPC&C. I'll try it again (I dont think I treid it with the combination of the Panamax)

I am using an Intel DG33TL because they are more stable than the rest... my other thought would be a Mini-ITX Via Epia (C7 processor) build which I may tryout since I can have the power supply external to the case...

In my build its actually a lower noise floor when the CPU is being used... if its idle the noise floor is much more readily appearent.

Thats awesome news about the buffalo because I am in process of buiding one... I got half the parts now just waiting for the next set of buffalo boards... maybe I'll hold out until they implement the 9018 .. not sure...

The custom USB or firewire is above the scope and my ability level unles someone develops a DIY kit... I am going to us the 27** serires for USB I2S....

Would SPDIF be better out of the M-Audio at that point? I'll probably try both anyway but I would love to hear opinions/experiences on the matter...
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Old 1st February 2009, 12:10 AM   #6
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Quote:
Originally posted by HaLo6
thanks! Am I far off base in thinking the digital USB should better less prone to PS noise than the PCI Sound card?

I am not an expert but have been following a number of threads on using a PC as source for a couple years. Most all recommend using USB DAC's I started with a PC running Win XP and in the last year moved to a Linux environment following the advice in this thread:

Linux Audio the way to go!?

Linux Audio the way to go? It is now a long thread, but the recommendations are contained in a WIKI here:

http://www.diyaudio.com/wiki/index.p...igital+Sources

It is more involved to setup, but for me the results were worth the effort.
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Old 1st February 2009, 12:31 AM   #7
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Can you explain abit more about what you meant by noise floor you heard from your speaker? The SMPS used in computer has very high switching frequency noise which will not show up as audible noise. However, if you are using the analog section of the sound card, there are many factors that can cause audible noise, even if your sond crad is placed too close to the AC line will cause that.

In my PC setup, I am using RME HDSP 9652 with ADAT out in digital. I use an external DAC. This way, I can elimnate all noise from the PC, there there is no issue of grounding problem as well.
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Old 1st February 2009, 03:08 PM   #8
HaLo6 is offline HaLo6  United States
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I am using the analog out of the M-Audio. The noise coming out my speakers is a slight hiss. Its only audible if I put my head next to the speaker... but we are all here at this forum b/c everyone is an audio perfectionist... Now the audio card is next to the PS but it is separated by a metal panel. Its in the only slot it can go in, (their is only one PCI slot on the DG33TL). Maybe thats the issue... if using USB I2S out wll solve this then I will look no further...
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Old 1st February 2009, 05:45 PM   #9
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I think the Antecs usually come with good quality power supplies. When I was looking for a case I settled on the Antec fussion. The Earthworks PSU I have seen reviewed and compares favourably with aftermarket PSU. Antec do use a made for them version, but the internals looked identical to the eathrworks.

Personally I use a DDDAC 1543 Dac on my main system, and dont notice any hum etc. I wonder if the noise you are getting is the sound card picking up EMI from other components in the case. Off board is easier to control for EMI. When I was testing my DDDAC uncased I got pretty poor sound quality from it.

I have sitting beside me a Y1 (Gamma 1) DAC that I just bought from Ti Khan at AMB labs I am looking forward to getting it assembled and tested. It is going to be my DAC for my eee PC 901.
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Old 1st February 2009, 06:50 PM   #10
Key is offline Key  United States
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If it's only slight you may not have anything wrong at all. How hot do you run your amps? How loud do you usually stage the gain coming out of the card to the amp?
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