Fixing USB DAC Issues

So I got this wonderful amp/DAC combo and headphones. Guess what! There is a terrible audio popping while listening to music on my computer! How can this be?! I spent so much money and this DAC is crap! Oh wait, it’s not the DAC. Or the amp. Or the headphones.

The first thing I did was Google to see if there was some known issue with the ODAC or Windows 7 and USB Audio. I found this thread on Head-Fi which referenced the ODAC. I also remembered a while ago that I dug out my old SoundBlaster Extigy external sound card to see if it would make a quality difference and it had the same issue. It couldn’t possibly be my computer, could it?

Let’s Talk About USB Ports

Turns out that USB audio needs a fair amount of bandwidth. Depending on how your computer is setup you may run into the same issue that I had. When I first plugged in the ODAC I got a warning about exceeding the bandwidth of my usb hub. I changed ports and the alert didn’t come back. I still had the popping and clicking noises.

Using the thread on Head-Fi as a basis I started looking into the device manager. I found a USB hub that did not share any IRQ with any other devices. This didn’t see to solve the problem. What I did find was under the Advanced tab was information about the amount of bandwidth used.

USB Hub With One Device

USB Hub With One Device

The above picture shows a USB host controller with a single device plugged in. I think this particular host is driving my keyboard. Notice the System reserved value. It’s at 10%. All the hosts had this amount. With I added up the percentage of bandwidth used for each host and came up with a number around 60-64% without the ODAC in use (my phone and mouse would fluctuate). When plugged in and in use the ODAC would use upwards of 40% of the bandwidth. My thoughts are that this much bandwidth usage was too much for my onboard USB.

Solution

After unplugging all my devices and doing a test I still saw that with all my host controllers using 10% for System reserved. That lead me to believe that even with just the ODAC plugged in I would be pushing 100% bandwidth usage. I decided that I should try installing a separate USB expansion board that took the load off the motherboard.

On to Amazon! I am so, so happy I am a Amazon Prime member!

I found this card on Amazon. It seemed like a good price and had some good reviews. I ordered it and a ‘Y’ cable. The card arrived this morning and it was a snap to install. I downloaded the drivers for the card from the support page. The only problem to report with the install is that I had to keep manually pointing the Windows driver installer to the directory where I extracted the files. Windows came back twice saying that it couldn’t find a driver.  Each time I pointed the wizard to the directory where I extracted the file and it found what it needed.

Once the card was installed I plugged in the ODAC. The computer was just as happy as normal. I couldn’t find the Hub that had the ODAC hooked up to it so I can’t see the amount of bandwidth consumed. However, the issue is now fixed! I couldn’t be more happier with the sound coming out of the headphones!

Realization

I spent over $600 on my awesome amp/DAC and headphones and it was stifled by the lack of a $20 discret USB card. Ouch!

About Mike

I'm a software engineer. Look into the about page for more information about me.
Tagged , . Bookmark the permalink.

Leave a Reply