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I'm using a Logitech USB Desktop Microphone.

It works perfectly when connected directly to the PC. However, if I connect it via a USB hub, it still is recognised, but I get all kinds of crackles and distortions.

How can that be? Shouldn't this be completely digital? How can the USB connection affect the recorded sound? Any troubleshooting tips to find the cause and/or fix this?

UPDATE: I bought a Belkin active USB hub. It seemed to be not-very-low-quality, but unfortunately it shows the same issues. :( Recommendations of specific USB hub models are welcome, I don't really know how to choose one that doesn't have this problem.

UPDATE 2: Is this maybe a problem with my specific microphone? Do you think another USB microphone would work on the same USB hub?

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How can it be completely digital? You're talking into the microphone. (Unless you're a robot speaking digital data into the microphone, in which case the answer is to speak in a digital error correcting code so the crackles and distortions don't matter.) – David Schwartz Nov 13 '11 at 20:33
@David Yeah, for some reason I assumed the crackles would be inserted at some point after the recording. While transferring the bits, basically. That's not the only way, of course. It didn't occur to me that the recording itself could already be affected. – hheimbuerger Nov 14 '11 at 9:01
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@David, funny, but the question clearly states that the same mic connected directly to the system works fine, without static. He obviously means that the data coming out of USB end of the microphone is digital, not analog. – Synetech Dec 8 '11 at 20:56
@Synetechinc. If he meant that, then he would have said, "This is completely digital". But he said, "Shouldn't this be completely digital". Surely he knows USB itself is digital, so what he's really asking is whether the entire path is digital -- which of course it isn't, and that explains his problem. – David Schwartz Dec 9 '11 at 18:54
@David, huh? No. He knows that USB transmits digital information and whatever the microphone sends should be in binary format. You are forgetting the he already said that it works fine when connected directly. Therefore, he is correct in assuming that if the mic creates clean output, and USB transmits in binary, then why would adding an extra digital device in between create static? Of course the answer is makes sense in this case, but if instead of a mic, it were a simple button, then he would be absolutely correct in wondering. – Synetech Dec 10 '11 at 22:23
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2 Answers

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Bad grounding affecting the analog circuitry in the microphone-preamp-ADC portion which then gets encoded in the digital signal sent to the computer.

Microphones tend to have ground shielding. Having it connected to the computer guarantees the integrity of that shield. Having it plugged into a hub, especially a cheap one doesn't guarantee that you have a true signal ground continuous from the mic, all the way to the computer. The ground shield on the microphone is probably floating, leading to electrical noise.

Upgrade to a high quality hub. Gold plating doesn't necessarily guarantee this as it's often added as a cheap and flashy way to visually impress. The contacts within the cable and the internal circuitry of the hub are way more important.

In the end, you will probably find that you need to have the mic directly connected to the computer to ensure good grounding. Alternately, get a quality extension USB cable, it will be cheaper.

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A direct connection might not be an option, but thanks for you detailed answer, it makes a lot more sense now. – hheimbuerger Nov 13 '11 at 19:13
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+1! It seems that not enough people mention the horrors found in cheap USB hubs... – AndrejaKo Nov 13 '11 at 21:12
Thanks! The shell is supposed to be tied to a ground plane that ties all the USB connectors together. I've opened them up and found that all the shell was used to do was to solder down the connector to the board as an attachment device. Yep, that's gonna work. – Fiasco Labs Nov 13 '11 at 21:22
I’ve seen the ground connected to a a piece of foil-covered cardboard in some devices. :-| It’s one thing to connect the “ground” of a jumper-cable to the chassis of a car, but I don’t think a small piece of tin-foil is quite going to cut it. – Synetech Dec 8 '11 at 21:06
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Interference. The connection between the USB Mic and the PC (without the hub) has nothing in-between (no electrical signal interference). When you plug it in, you get interference.

Try upgrading to a gold-plated USB hub.

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I think so too. – Chris Nov 13 '11 at 17:46
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Were you serious about the gold-platedness? I can't find any gold-plated USB hub. – hheimbuerger Dec 8 '11 at 20:44
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@hheimbuerger, and why would you? Gold-plated connectors are usually reserved for audio-video cables and connectors, not data. If you do managed to find a USB hub with gold-plated connectors, expect it to be laughably expensive. – Synetech Dec 8 '11 at 21:01
@FiascoLabs SuperUser is not for shopping/buying recommendations. This is not the site for you to sell your extra cable. – wizlog Dec 8 '11 at 22:07
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This answer suggested a gold-plated USB hub. – Synetech Dec 12 '11 at 21:36
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