Power line noise and USB audio - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, etc.

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
Reply
 
Thread Tools Search this Thread
Old 30th May 2006, 02:14 PM   #1
jmar is offline jmar  United States
diyAudio Member
 
Join Date: Jan 2004
Location: Indiana
Default Power line noise and USB audio

I have a PCM2902 that is using it's own power supply...nicely built on a PCB...works great except that if a glitch is imposed on the power line through something healthy like a refrigerator or a flourescent fixture on/off, it will disable.

If I go to device manager, I won't see "USB audio device" and the USB composite will show an exclamation mark of not installed.

If I reboot.....everything is fine until another AC glitch.... and it happens again.

I have the power supply filtered well on the LM317 input and output but still having problems.

Both jet audio and media player have been used.

Has this been a problem for anyone else?
  Reply With Quote
Old 30th May 2006, 03:40 PM   #2
jahonen is offline jahonen  Finland
diyAudio Member
 
jahonen's Avatar
 
Join Date: Jan 2002
Location: Kuopio, Finland
Does it the same when the audio is not connected, i.e. the USB cable is the only one connected? Try disconnecting the cables to find out which one is the interference source. For power, try using USB-power or just ordinary battery.

Problem is most likely common mode interference, it still remains regardless how much conventional (differential mode) filtering you apply.

Regards,
Janne
  Reply With Quote
Old 30th May 2006, 04:22 PM   #3
pburke is offline pburke  Germany
diyAudio Member
 
Join Date: Nov 2003
Location: Madison Wisconsin
just a guess: the problem may be the computer's power supply dropping out at that point. Power on the USB bus is required to sense the devices on the built-in ports

try the computer on a big UPS - not a bad thing to get anyway. There are tons of cheap units on ebay that'll do the job for these brownout moments

Peter
  Reply With Quote
Old 31st May 2006, 12:54 PM   #4
jmar is offline jmar  United States
diyAudio Member
 
Join Date: Jan 2004
Location: Indiana
I have the unit self powered, so I have the USB power line completely disconnected....(pin 1 on USB connector does not see pin 3 on the PCM2902).

Pin 1 isn't connected at all.

I was concerned about this at one point but thought it wasn't a problem?
  Reply With Quote
Old 31st May 2006, 02:12 PM   #5
jmar is offline jmar  United States
diyAudio Member
 
Join Date: Jan 2004
Location: Indiana
Also....

It only has this problem with the PCM2902 interface.

If I switch back to my sound card, it won't react to a glitch.

Sometimes I have to reboot, but lately, if I turn on/off the flourescent fixture (which is on the same circuit)....it will just stop the song.

I can hit play again and it will function but it always takes the windows volume control down about 50%.

It will do this wih both Jet audio and media player.

I'm going to try some more noise suppresion but sure would like some clues on this.

Thanks.
  Reply With Quote
Old 31st May 2006, 02:26 PM   #6
jahonen is offline jahonen  Finland
diyAudio Member
 
jahonen's Avatar
 
Join Date: Jan 2002
Location: Kuopio, Finland
Like I said, try to determine the coupling path of the interference (which disrupts USB-line communications). Does unplugging of the audio output cable (i.e. disconnecting the output cable and then playing music and experimenting with the light switch) entirely have any effect?

If you experiment with the filter, I suggest that you'll add some common mode filtering, unlikely the differential mode interference is the problem.

Regards,
Janne
  Reply With Quote
Old 31st May 2006, 02:29 PM   #7
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
just a guess -- the Codec demands 50 to 60 ma -- if you are using a 1,000uF storage cap on the LM317 it will discharge to less than 3.3V (from 5.0V) in 30 milliseconds or so --

i can knock out the device manager for my data-acquisition cards if i overload the current -- won't recognize the device until a hard reboot.
  Reply With Quote
Old 31st May 2006, 02:41 PM   #8
jmar is offline jmar  United States
diyAudio Member
 
Join Date: Jan 2004
Location: Indiana
I'll be damn....if I disconnect the RCA's from the board it won't do it.

I have an AD823 opamp on the output of the PCM2902.

Now that I look at this board closer, I forgot to add some filtering components I had made room for on the board....a 470pf across the output and a 100k for impedance setting.

OOPS.....maybe that will clear it up....I'll let you know.
  Reply With Quote
Old 31st May 2006, 03:04 PM   #9
jmar is offline jmar  United States
diyAudio Member
 
Join Date: Jan 2004
Location: Indiana
Well....no change, but definetly it's getting back to the computer through the receiver RCA jacks.

I have 470pf caps across each output but no change....also added the 10 ohm resistor between digital and analog grounds (which I had left out).

No hum at all in the thing....dead quiet....did have a ground loop that I cured initially.

Still acting up though...in fact now, not only will it stop the song when I hit the light switch but it will start it again if I turn it back on.

???
  Reply With Quote
Old 31st May 2006, 09:28 PM   #10
jmar is offline jmar  United States
diyAudio Member
 
Join Date: Jan 2004
Location: Indiana
Jacjinnj....

I don't have a problem unless these RCA cables are connected to the amplifier.

So that eliminates any power supply problem.

I think somehow the data (D- and D+) is being corrupted by the induced noise....what is wierd is that it that the audio will actually turn on again if I play with the light switch enough.

How can any of this be a power supply problem?

Would a flourescent switch actually cause line voltage sag?

Perhaps there is a grounding design flaw on the PCB but I sure don't "hear it".
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
How to remove noise from DC line? tripathdude Digital Source 1 20th March 2008 04:26 PM
Noise in my Line Splitter - HELP weston530 Parts 2 4th July 2005 07:13 PM
EDN on Line Noise, Hash, Nasties jackinnj Everything Else 0 19th March 2004 10:14 PM
Transmitting audio over power line paulb Solid State 3 5th April 2002 08:08 AM
Power Line Noise Thoth Everything Else 18 5th September 2001 01:55 AM


New To Site? Need Help?

All times are GMT. The time now is 04:02 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2