[Yardstick]

I need some help narrowing down a DAC or DAC/AMP combo for computer audio. The primary purpose is for playing music through over ear headphones while I'm working but I might use it for JBL 308s too. The 3.5 mm audio out jacks on the motherboard and case of my desktop are noisy. There's an audible hiss in quiet parts of songs or if there's no audio playing. There's some other hiss that comes in when the mouse moves and another screechy one that comes in with the scroll wheel. It's worse in some applications and it can be different depending on the browser page that is up (even if I'm working in another application). It's really weird. My monitor uses an HDMI signal so I tried plugging into its 3.5 mm plug. The audio is cleaner but it's also tinny and hollow. It lacks the fullness that I get from the motherboard audio. I had a first generation Schiit Modi/Magni combo that worked really well but the Modi died with fairly low use just outside of the warranty period and they were no help on that, so I'm a little apprehensive about buying their stuff. Is there something up to about $200 that would improve my computer audio? I still have the Magni, so I could go with a standalone DAC but I'm not sure I trust the Magni to last.

 

[Achlys]

Apple Dongle.

 

[Yardstick]

Apple Dongle.

I did a quick check and couldn't find a compatible Apple Dongle. This is for a PC with USB 2.0 and 3.0 outputs.

It's more than I was originally thinking of spending but the S.M.S.L M500 looks like an interesting option.

Funny update - I saw a review of a Schiit Modi 3 somewhere that talked about the DAC not being recognized by Windows shortly after their warranty expired. Based on a quick search it seems like that is a common problem. When it initially happened I tried different cables, different computers, different operating systems, etc... The reviewer said they heated their Modi with a hair dryer and then Windows recognized it. I dug out my Modi, plugged it in with its original cable and got the same 'unrecognized USB device' message I saw when I gave up on it. I opened the case and hit it with some hot air from a heat gun. Sure enough, Windows recognized it right away! I have AKG K553s plugged into the little Schiit stack right now and it sounds.... okay. It has a fuzzier background than I remember. The fuzz is mostly in the right ear. It is inoffensive when louder, busier music is playing, but quite noticeable in quieter parts of songs. At least it doesn't pick up mouse interference the way the PC does. There's an additional scratchy fuzz associated with the volume knob on the Magni amplifier. That also primarily comes through the right ear cup. The sound seems a tad flatter or even mid-forward than audio straight from the PC. It's interesting that heat seems to have fixed the problem with the Modi, but it seems like I still have a noise issue I need to find and fix.

 

[redrol]

You are experiencing a ground loop. Have you tried power cables to the JBL with no ground pin?

 

[Yardstick]

No, I haven't tried power cables without a ground pin on the JBLs. They don't seem to have as much background hiss as the headphones. They are plugged into a 3.5mm jack on the back of the motherboard. The headphones are quieter when plugged into that jack too. The plug on top of the case is more convenient for headphones since it's easier to switch between sets without pulling the whole case out. That plug is wired to the board and I'm guessing it isn't shielded as well. That's probably a big source of the noise. When I get a chance I'll do some more experimenting with the cabling and accessories plugged into the machine to see if I can narrow anything down further.

 

[redrol]

Ohhh hmm. Id recommend disconnecting the front audio jack from the motherboard. The reason being the audio jack on the front is connected to ground via the USB port cluster. Worth a try..

 

[Yardstick]

It looks like there are two cables from the motherboard to the little cluster of connections on top of the case. There's a microphone and headphone jack and then several data connections, including two USB ports. Maybe I can isolate the audio connections and disconnect or depin the others. I don't want to disconnect the whole thing because that's a really convenient place to plug in headphones since they can be switched without accessing the back of the computer.

 

[redrol]

yeah... not sure, I had to unhook the whole cluster

I'd still just try and unplug the thing and see if it works before going nuts.

 

[Yardstick]

The cluster with the audio ports has a Firewire and two USB connections. There's another board in close proximity with an eSATA connection too. I found a pinched ground wire that wasn't actually grounded except where it was pinched. It was between layers of the case so it must have been assembled that way. That ground belonged to the Firewire cable and wasn't doing anything since the Firewire connection wasn't plugged to the MB. For some reason the ring terminal of that ground was screwed into one of the plastic legs that was holding the audio/USB/Firewire board. Apparently I didn't look closely at that board when I built the machine so long ago. Anyway... Removing that extra cable didn't do anything. Unplugging the USB cable from the board has fixed the issue. Now that audio out on top of the computer case is silent when nothing is playing. Those USB ports were convenient, but I can live without them. I didn't realize how prevalent this problem is. There are quite a few threads on other forums describing how and where to cut through grounds on those USB/Audio boards to separate the grounds and get rid of background noise. If I want those USB ports back I might do some PCB surgery. For now I'll just enjoy the background noise free audio! Thank you!

 

[redrol]

Heeey, great to hear! And also I am not a total idiot with PCs. haha