PCM2702 on / off noise

Douchekop · 15th May 2005, 02:56 PM

I'm building a USB soundcard with a PCM2702. I have built the thing on a breadbord to test it. It sounds pretty good, but when I unplug the USB connector from my laptop or when I turn off my computer I hear a very anoying noise.

This is very anoying because I have my headphones on when I turn off my laptop.

How can I get rid of this noise?

Do you have any other advise for my project?

tobias_svensk · 15th May 2005, 04:42 PM

Perhaps putting a inductor on the Vbus line? It could be some voltage fluctation when you pull out your plug.

http://www6.head-fi.org/forums/showthread.php?t=105088
http://www6.head-fi.org/forums/showthread.php?t=109671

Ask them if they hear any noise, because they have a inductor on that Vbus

Douchekop · 16th May 2005, 10:29 AM

I placed a 100uF capacitor between Vbus and GND. With the USB output resistance, it functions as a low pass filter.

The off noise is fully eliminated, but there is still a small on noise. I think the on noise is now produced by the charging of the 100uF capacitor. I will try a smaller capacitor.

I will also try a coil in the Vbus line. That functions as a low pass filter too, but maybe it works better.

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15th May 2005, 04:42 PM	#2
tobias_svensk diyAudio Member Join Date: Jan 2004 Location: Hudiksvall	Perhaps putting a inductor on the Vbus line? It could be some voltage fluctation when you pull out your plug. http://www6.head-fi.org/forums/showthread.php?t=105088 http://www6.head-fi.org/forums/showthread.php?t=109671 Ask them if they hear any noise, because they have a inductor on that Vbus

16th May 2005, 10:29 AM	#3
Douchekop diyAudio Member Join Date: Jun 2003 Location: Sint Oedenrode	I placed a 100uF capacitor between Vbus and GND. With the USB output resistance, it functions as a low pass filter. The off noise is fully eliminated, but there is still a small on noise. I think the on noise is now produced by the charging of the 100uF capacitor. I will try a smaller capacitor. I will also try a coil in the Vbus line. That functions as a low pass filter too, but maybe it works better.

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