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What's the deal with amplifier hiss?

post #1 of 26
Thread Starter 

I have a Tube Magic D1 as my amplifier/source. On my home computer, a constant hiss starts to be introduced at around 1 o'clock and gets louder as I turn the knob higher. This is a slight problem, as some of my quieter recordings of classical music require me to bring the knob to about 2 o'clock. However, when using the D1 with my Sansa Fuze, there is 0 audible hiss at any volume level. I'm currently using the D1 with my friend's Macbook and the hiss is also much less than my home computer, not becoming noticeable up until about 4 o'clock.

 

What can I do to remedy the hiss problem with my home computer? I'm thinking that it's the motherboard/USB inputs. I bought the computer pre-built and the motherboard isn't exactly high quality. I don't think it's the PSU, since I recently upgraded from the stock 220w PSU to a nicer Corsair 430w PSU.

 

If anybody has any ideas, it would be greatly appreciated. Thanks!

post #2 of 26
Thread Starter 

Nobody knows? :(

post #3 of 26
I'm no expert by any means but I've learnt that DACs are great for using with computers as they clean up the sound from pc and laptops and output it at a higher quality, the fiio e7 gets some very positive response in reguards to this
post #4 of 26
Get a better source. What you are hearing is the noise floor of your sound card. As you demonstrated using different sources produced lower noise. So get a different source, USB dac might work well for you.
post #5 of 26
Thread Starter 

Yes, the D1 is a USB DAC. The problem is that the floor noise is louder depending on what I use the D1 with ex. home computer, friend's Macbook, or Sansa Fuze.

post #6 of 26

Are output levels the same (i.e. when you use the Fuse with the D1 at 4 o'clock, does it play at the same volume as your computer with the D1 at 4 o'clock)? Usually noise is some combination of electrostatic interference (like from the insides of the computer, from the USB lines), cheaper amps, cheap sources, etc.

post #7 of 26
Thread Starter 

Yes the volume is exactly the same. The only difference between me using my home computer and the Macbook/Fuze is that there is more hiss with my home computer.

post #8 of 26

Has the hiss always been there, or did it only start recently? If it started after upgrading your psu, that's probably the culprit.

 

Other probable causes (which are not mutually exclusive): ground loops, dirty/usb bus


 

post #9 of 26
Thread Starter 

Could you explain the principle behind a ground loop? I've looked it up before but I'm still a little foggy on what exactly it is and how to fix it. Also, I have tried it through different USB ports on my computer but I think that it's just that all of them aren't very good. If I upgraded to a nicer motherboard (with USB 3.0?), do you think it would help?

post #10 of 26

It seems to be a common problem. Time to upgrade :p.

post #11 of 26
Quote:
Originally Posted by tangelo View Post

Could you explain the principle behind a ground loop? I've looked it up before but I'm still a little foggy on what exactly it is and how to fix it. Also, I have tried it through different USB ports on my computer but I think that it's just that all of them aren't very good. If I upgraded to a nicer motherboard (with USB 3.0?), do you think it would help?


Here's a really long article on ground loops... http://www.diyaudio.com/forums/diyaudio-com-articles/163575-audio-component-grounding-interconnection.html?garpg=4

 

The gist of it though is that your "ground" winds up getting noise injected because it's connected to different devices. Identifying and eliminating ground loops are difficult and at times maddening. The "noise from a computer" is especially difficult to track down because it could be a ground loop or emi or a shoddy power supply or a noisy usb bus or any combination of those.

 

I ask again, when did the noise/hiss start? Was it the same time you upgraded your psu? Have you added any other devices to the computer? Is there anything else plugged into the same power strip or same wall outlet?

post #12 of 26
Thread Starter 

Thank you for the article, it has a lot of helpful information. As for your question, the hiss has been there ever since I bought the unit. Only recently did I try the device with my Fuze/friend's Macbook, which was when I noticed the reduction in hiss compared with my home computer. When I upgraded the PSU, the hiss stayed the same as far as I could tell. I have a mouse, a keyboard, a USB fan, and a microphone all attached through USB as well. The D1 is on a power strip with the monitor power cord and a power cord for a lamp, but I had it by itself earlier but noticed no difference so I moved it back to the power strip.


Edited by tangelo - 4/6/11 at 6:50pm
post #13 of 26

Try disconnecting some of the usb devices one at a time and see if it makes a difference. Oftentimes, another device drawing significant power from the usb bus will cause a lot of noise. High data transfer over usb can also cause noise, but in your case I would suspect it is more a power issue (if at all).

 

Another quick fix is to buy a ground loop isolator ($15 from radio shack) which is basically an RCA interconnect with a module (signal isolation device) in the middle.

post #14 of 26

Ok I used to have this problem when I first started using USB dacs and initially thought it was a problem with the dac. Turned out I needed to mute the microphone on my laptop which was wierd since there was no mic connected. I guess it was picking up some interference in the motherboard.

post #15 of 26
Thread Starter 

So you're telling me something like this http://www.radioshack.com/product/index.jsp?productId=2062214 will get rid of all hiss with no degradation in sound quality? Also, suppose removing one USB device did reduce the hiss... is there a problem with that device and I should buy a new one? Like, what would I do to fix it? Also, would attaching all other USB devices in one USB hub with the D1 by itself do anything? 

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