Amp Picking Up PC Noise

Looking at the Rogue Audio Cronus Magnum I see there is no USB input?  If that is the case then your DAC in your PC is the culprit.  The best way to eliminate this would be to simply purchase a decent DAC like the Bithead from Headroom and have your PC feed the Bithead vis USB and then the Bithead feel the amp via stereo Y-Splitter to RCA.  Computers are notoriously noisy DACs.

 

A good DAC will reduce the noise you are hearing by at least 95dB.

Hardly. That would mean the PC's DAC would have to have 0 dB noise. All you'd hear is noise.

 

Davienr, have you done any checks to be sure it's the computer and not a fault with the amp? Tubes can be susceptible to interference from nearby wireless equipment, like a phone. You can try a cheap external DAC like the Behringer UCA202 to test.

 

If you honestly don't have a dedicated DAC, I think maybe you should have done more research before blowing $2,000 on an amp.

Make sure all the sound stuff, including your computer,  is connected to the same outlet, and nothing else.

That's strange, as a good intermediary device should cut out most of the discernible noise from your PC.  That's why people buy $20 USB sound cards.  I'd imagine the E7 should be sufficient, though I use a much cheaper device to deal with laptop noise.

 

I'd like to say that a good discrete DAC would solve your problem, but there seems to be something going on.

 

What are you using for your computer?  At the cost of a good DAC, you may be better served just building a new computer.  I'm assuming you're not using a Macbook Pro, as Apple computers usually don't have the noise lousy Dell (and other cheap PC OEMs) have.  I'm pretty picky about the components I use in my system and never have any discernible noise, but I can hear noise easily from a Dell Optiplex and other budget office computers.

No, the cover off shouldn't cause any issues.  I've left the cover off on a lot of gaming PCs to help with cooling while running SLI.  I'm suspecting a shoddy power supply and/or mobo.

 

How are you getting sound out of your PC?  PCI sound card or onboard audio?  Which chipset?  Analog or digital out (and if so, Toslink, coax, etc.)?

 

It's difficult to diagnose without more detailed information on exactly what you're doing.

Nice PC.  The issue probably isn't the mobo.  The Gigabyte Z68X should be fine.  CPU should have no effect.  What PSU are you using?  You didn't skimp on the other parts of your system so I assume you have a decent PSU.

 

If you're going from:

 

PC -> USB to E7 -> RCA to Magnum -> Headphones

 

Then I'm pretty stumped why the noise is being picked up on the USB cable, assuming there's nothing wrong with the cable.  I'm also assuming all your gear is properly grounded.

 

The only suggestion I have is make sure you're not using DirectSound for music playback, and instead try using WASAPI output through Foobar and see if that helps.  Foobar automatically claims exclusive mode when using WASAPI, so you won't be able to get sound through anything else until you stop playing music on Foobar.

 

Let us know if that helps at all.  If you plan on getting a good DAC, I'd just return the E7 and get something like a AMB gamma2 (if you don't want to build one yourself, you'll have to commission one), and use coax or Toslink for it.  There are a lot of good popular $300-500 DACs nowadays.

 

From looking at your mobo, it looks like you've got digital out.  In my experience, most DACs don't do USB very well.  The latest generation of Gigabyte onboard implementations are good, so I don't think you need a PCI sound card to solve this issue.  If you have a PCI sound card laying around, I'd plug it in and output through that, straight to the Magnum, to see if it solves your problem.

Edited by Elysian - 11/9/11 at 2:21am

I'm almost shure its a ground issue and offcourse a fan issue... I have the same problem when i'm playing just music the noise is not realy anoing but when i"m downloading a lot(usenet so a lot of pc power needed) or playing games my fans and hard disks spin a lot faster and the noise increases, the only thing that helped me out was conecting with spdif because there is no way the irritating sound can travel with a bitstream over light(spdif) so i asume you should get a dac with spdif on IT.... Its a fairly costly procedure but if you are willing to pay the price the end result will realy be satisfiing. Its a hissing sound you hear right? IT comes from the motors of your fans and hard disks, just try to stop some fans and listen again(i hope you are smart eneough to now how to stop a fan, and dont do this for a long time! I noticed that the fans used on video cards are realy cheap and do spin spin realy fast but also give extra noise)
Edited by acc focus - 11/9/11 at 4:34am

With the E7 set the screen to turn itself off, this reduces noise also get the L7(the line-out dock for the E7) , tube dac/amps can have really bad signal to noise ratio they measure around 60db signal to noise ratio which means audiable noise, so it might be the tube amp causing the noise. Have you tried using the E7's headphone jack and see how much noise you can hear?.