USB Microphone


Senior Member
Shout toward the clever folk...

I have a USB microphone here that doesn't have a lead. I found an XLR plug and an old USB 4 core lead and assumed I could make my own.

Lower left hand connections appear to be the 5v supply, no problems there (I don't think). The SMT fuse is ok (the microphone is new) and when plugged in, I get 5V at these terminals.

Right hand lower connections I assume to be the signal/data. Minus pin of those two seems to common to ground.

But... when its plugged into the USB port (via a diagnostics USB module), it does not pull any load at all.
Now the third pin on the XLR is the unknown. I would have thought it was the green data lead, but that doesn't do anything.. neither does the white data lead. Which is + and - data I do not know... Google that and you get a varied answer.

The larger chip is an echo processor, so I would have though that would have pulled a small load once the pcb was powered?
Bottom right 8 pin chip is an op-amp I believe.

So... here are my thoughts..

1/ The microphone is broken. Not likely, its new.
2/ The data leads in the USB need some kind of signal/resistance to turn on the microphone? Seems a bit unlikely
3/ The lead should actually be a 6 pin USB. However there are only 3 XLR pins going into the microphone, so you would just have more spare pins.

Any ideas?


Technical Support
Staff member
It looks like you are trying to put the 4 USB signals through a three core XLR cable. That won't work; all four signals are required for USB.

Three signals to the PC's USB ( 0V, D-, D+ ) may be usable if you supply a separate 0V/5V power connection to the microphone PCB.

The "-" you have labelled "0V" may actually be "D-".


Senior Member
Hmm. I though maybe it was using the supply 0v as the signal common.

It must be 3 core... its only got a 3 pin XLR plug going on to the microphone. The mic originally came with a usb to XLR lead, but my son lost it.

I am now wondering if the USB supplied only the power, and the microphone output was separate to a 3.5mm jack


Technical Support
Staff member
Looking more closely at the photo it appears it's an XLR connector at the end of the microphone.

If so, the XLR-to-USB cable you had was probably an interface which takes analogue via the XLR, processes that with some chip inside the USB plug, delivers USB.

You would need to create an Analogue to USB interface to get the XLR connection into the PC USB port. You can't plug the XLR into the USB port using a hacked cable.

In short; it's not a "USB microphone", it's an "Analogue microphone" with an "Analogue to USB cable".

Extra Added: Or maybe not even that. It could be that the cable was XLR to 3.5mm jack plus a USB connection which simply provides power.

Perhaps tell us what make and model this microphone is and that might point to something which explains how it is meant to be used.
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Senior Member
Thanks Hippy.
After trawling around Google, I found an image of the microphone and sure enough... it is an XLR plug that then splits into a USB and a mono 3.5mm.
So, 5v to the left hand side of the pcb, and the XLR screen is the microphone screen. Third XLR pin is the microphone signal.
All working now.

Odd that the unit seems to show zero load on my USB volt/amp monitor. Perhaps its just not a very sensitive monitor