USB sound cards

You probably meant noise, not jitter. This noise is caused by the on-board circuitry picking up interference from other components inside the computer (usually fans and hard drives).

 

It's hard to say if a USB DAC/Amp can completely eliminate the background noise, it depends on how clean is your USB power, how high is the gain used in the headphone amp, and on your headphones impedance and sensitivity.

Your headphones have low impedance and are easy to drive, so you should prefer low gain devices (that translates to less volume knob range to spare).

 

I'm using the Behringer UCA202 (~$35) with the HD555 and it works great (zero noise, great sound), but I can't guarantee it will work well with the M50 because it (the Behringer) has a rather high output impedance (~50ohm), and that may cause significant freq. response variations on some headphones.

I had good results in eliminating the computer noise with http://www.turtlebeach.com/products/sound-cards/audio-advantage-micro-ii.aspx

and it was just over $20. It works well with all of my headphones.

onboard jitter (Noise) is caused not only by fans and hard drives, but by improperly grounding the circuitry. In my dell, there has been this persistant high pitched whining noise. After much research and hassle and getting everything in the laptop replaced, i realized that the most obvious solution was the correct one: wrap the entire sound board in duct tape. I literally pulled it out, wrapped it up in masking tape (duct tape or electrical tape would be much better. I have electrical tape around it now), and shoved it back in. I was careful to try to isolate the screw too. This essentially created its own mini ground hooked into a "resistor" so to speak. What was happening was that electricity was forcing its way up the ground circuit and causing feedback. THis fix completely eliminated the problem.

With some sound cards or DACs that are powered purely by USB, the noise level is affected by the USB port.

 

A friend mine had a Creative X-Fi USB plugged into the front of his computer. The noise floor was audibly high when I listened to it. My friend described it as sounding kind of dull. I reasoned that the front USB port was the problem because on the inside it's hooked up to the motherboard via unshielded wires. So it's pretty much like an antenna that picks up EM noise from all the other computer parts inside the case. I unplugged the X-Fi and connected it to the back of his PC instead, and there was a big improvement.

 

 

ps You can try getting the Fiio E5 headphone amp if your soundcard's output impedance is too high. It's very cheap (~ $20) and has a low output impedance. You would hook it up like this: PC -> USB sound card -> E5 -> headphones.

 

Now, you say "USB Powered". Does this mean that if we test a sound card that uses an external power source that it would not have noise? what if we used the data in/out lines but grounded the usb power?

It depends on what kind of power supply used. A switch mode power supply used for most computer devices is cheap and compact, but also noisy. Replace that with a linear regulated power supply if you can. USB power is almost always switch mode. Even a laptop running on battery can have noisy power depending on how the battery voltage gets converted for USB.

 

Some USB DACs have good noise filtering built in. Ferrite beads and pulse transformers can be used for this. Lately there's also the ADuM4160 chip that galvanically isolates the USB data signal. You can buy a USB Isolator kit or something similar that incorporates this. ¹

 

Still, even with their limitations, USB DACs are usually much quieter than onboard PC sound or the typical sound cards. Just use the port on the back of the computer instead of the front.

Edited by Yoga Flame - 3/28/11 at 9:28pm

I was planning on building the Gamma 1, and eventually the Gamma 2 DAC. From what I saw, it uses ferrite beads in its construction, presumably to reduce noise.

I bought a cheap Terratec Aureon Dual USB (20€) to get rid of the noise and it works like a charm.

Of course it doesn't sound the same as the Xonar card on my desktop but it's fine for what I do with my laptop. Using ASIO4ALL in foobar2000 it sounds pretty good, but DS sounds a bit weird (I'm on XP), maybe the mixer is doing some dirty resampling because it sees the card as being capable of handling 48hz (but my music is only 44.1/16bit)

 

Volume level is good and there is not the slightest noise or anything, even though the PSU on my laptop sometimes makes horrid sounds. Mic entry is fine too (and loud enough)

 

Does not require drivers and works on Mac/Linux/Windows etc

Edited by kalston - 3/30/11 at 6:20am

Couldn't agree more. USB ports in the front are always prone to give issues, not only for audio (even if audio is more sensible). For laptops, external DACs, be it USB, Firewire, etc, are a perfect solution for noise issues, and for overall significant SQ improvements.