HELP: PC (USB) problems with Subwoofer – LOUD white noise

sunil · 03:30 AM

Hi,

I have a PC based audio setup (Ubuntu /USB). The USB output feeds a Firestone DAC that goes to an Audiolab preamp. The preamp feeds a Behringer 2310 and from there to the power amps. A subwoofer (Dayton 315 with Oaudio 500) is connected to the pre-out on the preamp.

PC (USB) --> DAC --> Preamp --> Behringer active X/O --> Power-amps

Preamp --> Subwoofer

Pulseaudio is used in Ubuntu and the volume is disabled. The DAC volume is set to ‘shunt’ mode and the pot fixed at 12’o clock.

Most program material plays fine. If there is deep bass and/or the volume is turned up the USB stream gets cut-off and replaced with very loud white noise from the main speakers. Turning the volume on the preamp down stops this. Restarting the audio player in Ubuntu (Audacious) does not bring the music back completely. There’s noise riding on the signal & the audio bit is very feeble.

Switching the amps and DAC off brings it back online, till the next ‘white noise’ break. So far, I’ve been able to play the system without problems if the SUB is switched off completely.

Weird – I don’t know, why – I have no clue. Has anybody seen this before ?
Can somebody please help me understand how to fix it.

P.S: If the moderators think this is in the wrong forum, please move accordingly – Thanks.

Thanks,
Sunil

erin · 4th July 2011, 06:20 AM

Just a suggestion. I have had USB audio signals disrupted by mains borne interference such as motors switching on and off. Perhaps the subwoofer is drawing a large current and causing mains spikes or fluctuations during loud passages?

The exact cause I dont know, but the point I am trying to make is that USB audio is not always 100% reliable when there is RF interference or mains disturbance.

Perhaps try using a shorter USB cable?

sunil · 4th July 2011, 04:02 PM

Thanks Erin. Separating the PS for the SUB is a huge task. What I can't understand is why it happens only when the volume is turned up ?

Anybody with opinions /experience, please help ?

erin · 5th July 2011, 12:03 AM

Sunil, I was not suggesting to relocate the power supply for the sub.

How long is the USB cable you are presently using?

sunil · 5th July 2011, 12:58 AM

I've tried the stock 1m cable, an extension 3m, both shielded and with a hub. The only thing left to try is a different power outlet because all the ones in the present rm are looped to the same line

The PC is ~3m away from the system console which makes it harder, cause then I have to go with longer RCA's. Do you think that makes better sense ? I'm also seriously thinking of a good soundcard, in the lines of ASUS , if this setup does not work.

Regards,
sunil

erin · 01:22 AM

I know someone who uses an Asus Xonar D2X (spdif output) powered with external linear power supplies and he thinks its very good. I have not heard it but I trust this persons opinion.

It seems like the problem is related to the sub. Is it a Class D amp inside the sub?
I wonder if it has CE, C tick, FCC approval? perhaps it outputs exceessive noise?

does the firestone DAC use an external (wall wart) power supply? I wonder if when the Sub is playing loudly that the vibrations are momentarily dislodging the power connector either at the power board or the DAC end?

sunil · 5th July 2011, 02:16 AM

I can't see any of those approvals on the plate amp. It was bought from Oaudio.
The problem is definitely the SUB.

The DAC does use an external supply, but its a tight fit on the power strip so I doubt the SUB is dislodging it. About the ASUS I was thinking of the 'Essence XT' since it has RCA out.

Looks like I'm out of options ?

erin · 5th July 2011, 02:32 AM

My last thoughts on the matter, are for you to try adding larger capacitance to the power rails of the DAC, or using a different preferably linear power supply ( with big capacitance), ferrites on your mains power leads, and perhaps seperate inline filters on the SUB and on the DAC. Perhaps the heavy power draw of the SUB is causing a voltage drop in the DAC causing it to loose comms with the computer?
Larger capacitance will keep the DAC at full voltage long enough to withstand the short term voltage drop on the mains.

sunil · 5th July 2011, 05:12 AM

Thanks Erin. I see my options as:

- Change the SUB ps to a different outlet
- Stiffer PS for the DAC
- USB2ISO isolator

I wonder if the US2ISO will solve the problems I'm having. It is explained as being able to isolate PC power problems. Could anybody please help me understand my situation ?

I'm posting this question on the USB2ISO thread to see if those folks have any idea about this.

4th July 2011, 03:28 AM	#1
sunil diyAudio Member Join Date: May 2003 Location: Bangalore, INDIA	HELP: PC (USB) problems with Subwoofer – LOUD white noise Hi, I have a PC based audio setup (Ubuntu /USB). The USB output feeds a Firestone DAC that goes to an Audiolab preamp. The preamp feeds a Behringer 2310 and from there to the power amps. A subwoofer (Dayton 315 with Oaudio 500) is connected to the pre-out on the preamp. PC (USB) --> DAC --> Preamp --> Behringer active X/O --> Power-amps Preamp --> Subwoofer Pulseaudio is used in Ubuntu and the volume is disabled. The DAC volume is set to ‘shunt’ mode and the pot fixed at 12’o clock. Most program material plays fine. If there is deep bass and/or the volume is turned up the USB stream gets cut-off and replaced with very loud white noise from the main speakers. Turning the volume on the preamp down stops this. Restarting the audio player in Ubuntu (Audacious) does not bring the music back completely. There’s noise riding on the signal & the audio bit is very feeble. Switching the amps and DAC off brings it back online, till the next ‘white noise’ break. So far, I’ve been able to play the system without problems if the SUB is switched off completely. Weird – I don’t know, why – I have no clue. Has anybody seen this before ? Can somebody please help me understand how to fix it. P.S: If the moderators think this is in the wrong forum, please move accordingly – Thanks. Thanks, Sunil Last edited by sunil; 4th July 2011 at 03:30 AM. Reason: Corrected the line drawing showing the setup

5th July 2011, 01:16 AM	#6
erin diyAudio Member Join Date: Nov 2006	I know someone who uses an Asus Xonar D2X (spdif output) powered with external linear power supplies and he thinks its very good. I have not heard it but I trust this persons opinion. It seems like the problem is related to the sub. Is it a Class D amp inside the sub? I wonder if it has CE, C tick, FCC approval? perhaps it outputs exceessive noise? does the firestone DAC use an external (wall wart) power supply? I wonder if when the Sub is playing loudly that the vibrations are momentarily dislodging the power connector either at the power board or the DAC end? Last edited by erin; 5th July 2011 at 01:22 AM.

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
How loud is 250uV white noise?	81bas	Solid State	5	9th April 2010 05:43 PM
White Noise Active PSU	ANDYLASER	Swap Meet	5	12th January 2009 06:37 AM
White Noise, Protruding woofer	Code	Class D	6	16th January 2008 06:02 PM
HELP: White or Pink noise problem	Tedyp	Parts	2	26th March 2006 10:42 PM
white noise in subwoofer, home system	lucksi	Everything Else	0	28th June 2005 04:40 PM

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

4th July 2011, 06:20 AM	#2
erin diyAudio Member Join Date: Nov 2006	Just a suggestion. I have had USB audio signals disrupted by mains borne interference such as motors switching on and off. Perhaps the subwoofer is drawing a large current and causing mains spikes or fluctuations during loud passages? The exact cause I dont know, but the point I am trying to make is that USB audio is not always 100% reliable when there is RF interference or mains disturbance. Perhaps try using a shorter USB cable?

4th July 2011, 04:02 PM	#3
sunil diyAudio Member Join Date: May 2003 Location: Bangalore, INDIA	Thanks Erin. Separating the PS for the SUB is a huge task. What I can't understand is why it happens only when the volume is turned up ? Anybody with opinions /experience, please help ?

5th July 2011, 12:03 AM	#4
erin diyAudio Member Join Date: Nov 2006	Sunil, I was not suggesting to relocate the power supply for the sub. How long is the USB cable you are presently using?

5th July 2011, 12:58 AM	#5
sunil diyAudio Member Join Date: May 2003 Location: Bangalore, INDIA	I've tried the stock 1m cable, an extension 3m, both shielded and with a hub. The only thing left to try is a different power outlet because all the ones in the present rm are looped to the same line The PC is ~3m away from the system console which makes it harder, cause then I have to go with longer RCA's. Do you think that makes better sense ? I'm also seriously thinking of a good soundcard, in the lines of ASUS , if this setup does not work. Regards, sunil

5th July 2011, 02:16 AM	#7
sunil diyAudio Member Join Date: May 2003 Location: Bangalore, INDIA	I can't see any of those approvals on the plate amp. It was bought from Oaudio. The problem is definitely the SUB. The DAC does use an external supply, but its a tight fit on the power strip so I doubt the SUB is dislodging it. About the ASUS I was thinking of the 'Essence XT' since it has RCA out. Looks like I'm out of options ?

5th July 2011, 02:32 AM	#8
erin diyAudio Member Join Date: Nov 2006	My last thoughts on the matter, are for you to try adding larger capacitance to the power rails of the DAC, or using a different preferably linear power supply ( with big capacitance), ferrites on your mains power leads, and perhaps seperate inline filters on the SUB and on the DAC. Perhaps the heavy power draw of the SUB is causing a voltage drop in the DAC causing it to loose comms with the computer? Larger capacitance will keep the DAC at full voltage long enough to withstand the short term voltage drop on the mains.

5th July 2011, 05:12 AM	#9
sunil diyAudio Member Join Date: May 2003 Location: Bangalore, INDIA	Thanks Erin. I see my options as: - Change the SUB ps to a different outlet - Stiffer PS for the DAC - USB2ISO isolator I wonder if the US2ISO will solve the problems I'm having. It is explained as being able to isolate PC power problems. Could anybody please help me understand my situation ? I'm posting this question on the USB2ISO thread to see if those folks have any idea about this.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)