USB Sound Card

GianLorenzo · 8th February 2005, 03:05 AM

Hi there,

I have just made a USB Sound card using a MAX4299 Stereo Amp and a PCM2900E Audio Codec. It didn't work properly at first, and whenever a sound was played a loud crackling sound would play, no matter what the actual output was supposed to be.

After spending ages error-checking and using an oscilloscope to work out where the problem was, I got the card to work perfectly but only if I connected the analog ground of the board to the ground of the oscilloscope. As soon as a I disconnected the oscilloscope ground, all I got was the loud noise again.

Does anyone have any idea why it would only work when attached to the oscilloscope ground, and if there is anything I can do to fix it?

Cheers

wes-ninja250 · 12th February 2005, 06:23 AM

You obviously have a grounding problem.

I take it you have amplified speakers. Are they by any chance grounded to the same ground as the scope? (I'll bet they are).

If so, I would immediately check the connector where they plug into the sound card, and the wiring to the speakers.

Wes

d3imlay · 12th February 2005, 09:28 AM

I presume you're using the +5v usb power for the board. Does the analog ground and power supply share the same ground wire? What happens if you use an external power supply?

For a different application i bought and used an isolated hub from these people.

http://www.bb-europe.com/

GianLorenzo · 16th February 2005, 06:33 AM

Thanks for the replies, turns out I had a 10R resistor in between analog and digital ground and that was causing the problem!

Thanks!

8th February 2005, 03:05 AM	#1
GianLorenzo diyAudio Member Join Date: Dec 2004 Location: Perth, WA	USB Sound Card Hi there, I have just made a USB Sound card using a MAX4299 Stereo Amp and a PCM2900E Audio Codec. It didn't work properly at first, and whenever a sound was played a loud crackling sound would play, no matter what the actual output was supposed to be. After spending ages error-checking and using an oscilloscope to work out where the problem was, I got the card to work perfectly but only if I connected the analog ground of the board to the ground of the oscilloscope. As soon as a I disconnected the oscilloscope ground, all I got was the loud noise again. Does anyone have any idea why it would only work when attached to the oscilloscope ground, and if there is anything I can do to fix it? Cheers

16th February 2005, 06:33 AM	#4
GianLorenzo diyAudio Member Join Date: Dec 2004 Location: Perth, WA	Thanks Thanks for the replies, turns out I had a 10R resistor in between analog and digital ground and that was causing the problem! Thanks!

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
PC sound card sound chips	kaluchka	Chip Amps	6	20th June 2011 03:48 PM
Which sound card?	MMeche	Digital Source	1	28th June 2008 11:17 PM
mic for sound card	ostie01	Multi-Way	0	24th April 2006 06:28 AM
What Sound Card for PC T&M	primalsea	Multi-Way	3	8th February 2006 02:08 AM
DAC/ Sound card	argonrepublic	Digital Source	0	11th July 2005 03:39 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

12th February 2005, 06:23 AM	#2
wes-ninja250 diyAudio Member Join Date: Feb 2005 Location: Kingston, ON	You obviously have a grounding problem. I take it you have amplified speakers. Are they by any chance grounded to the same ground as the scope? (I'll bet they are). If so, I would immediately check the connector where they plug into the sound card, and the wiring to the speakers. Wes

12th February 2005, 09:28 AM	#3
d3imlay diyAudio Member Join Date: Sep 2004 Location: Ohio	I presume you're using the +5v usb power for the board. Does the analog ground and power supply share the same ground wire? What happens if you use an external power supply? For a different application i bought and used an isolated hub from these people. http://www.bb-europe.com/