DAC interference problems - 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 14th September 2003, 01:02 PM   #1
MWP is offline MWP  Australia
diyAudio Member
 
Join Date: Oct 2002
Location: Adelaide, South Australia
Default DAC interference problems

Greetings all....

Ive just built up my DAC (PCM2902, DIR1703, PCM1730) and placed it in a nice 1U rackmount, etc.

Ive now got a very annoying problem with it.
Ive hooked up a led on the front panel to show the status of the DIR1703's UNLOCK pin (lit when recieving SPDIF data).

Every time there is some small disturbance in this rooms power supply (a light turning on, heater thermo turning on/off, turning the soldering iron on/off, etc), the UNLOCK led will go out for about 1sec (DAC stops working) and then continue like normal.

ATM im using the PCM2902 (USB "soundcard" IC) which then feeds the SPDIF signal directly to the DIR1703.

Anyone come across this problem before?

Thanks.
  Reply With Quote
Old 14th September 2003, 05:08 PM   #2
A 8 is offline A 8  Sweden
diyAudio Member
 
Join Date: Mar 2003
Location: Gothenburg
Default Powersupply....

You need a power supply that is more effective in suppressing noise on the mains.

If you share how you've designed the supply to your dac my guess is that you'll get a lot of advice.
  Reply With Quote
Old 15th September 2003, 02:02 AM   #3
MWP is offline MWP  Australia
diyAudio Member
 
Join Date: Oct 2002
Location: Adelaide, South Australia
Ok...

12-0-12 torodial.

For the digital supply: torodial -> half bridge to produce 17-0V smoothed with 4*2200uF electros -> 78M33 reg for 3.3V -> a few 0.1uF caps.

Cant be much more simple.
  Reply With Quote
Old 15th September 2003, 12:50 PM   #4
A 8 is offline A 8  Sweden
diyAudio Member
 
Join Date: Mar 2003
Location: Gothenburg
I've not had the problem myself but it seems to be enough.

Pehaps you should also consider the cdp to have the problem and/or the interface between them.


You could try a film or ceramic in paralell with the 4 2200uF and or an inductor in series between the rectifier and the smoothing caps.
  Reply With Quote
Old 15th September 2003, 01:31 PM   #5
Bricolo is offline Bricolo  France
diyAudio Member
 
Bricolo's Avatar
 
Join Date: Nov 2002
Location: Grenoble, FR
you could try with an ac filter

it's easy to try, you just have a ready to use filter to plug between the ac inlet and the trafo
and it only costs a couple of $
  Reply With Quote
Old 15th September 2003, 04:22 PM   #6
MWP is offline MWP  Australia
diyAudio Member
 
Join Date: Oct 2002
Location: Adelaide, South Australia
Ok, thanks ill try those things.

Could grounding be a problem?

At the moment the chassis is earthed.
But the DACs ground is isolated from the mains-earth/chasis.

I thought this might help to reduce ground loops... but might it be causing this problem?
  Reply With Quote
Old 15th September 2003, 04:33 PM   #7
Bricolo is offline Bricolo  France
diyAudio Member
 
Bricolo's Avatar
 
Join Date: Nov 2002
Location: Grenoble, FR
Is the ground totally isolated from the earth? (floating)
If so, you could try connecting signal ground and earth with a resistor (10R, 5W) or 2 parallel diodes (but one in each polarity)
  Reply With Quote
Old 16th September 2003, 09:49 AM   #8
diyAudio Member
 
Join Date: Dec 2001
Location: Eindhoven
Default Re: DAC interference problems

Quote:
Originally posted by MWP
Greetings all....

Ive just built up my DAC (PCM2902, DIR1703, PCM1730) and placed it in a nice 1U rackmount, etc.

Ive now got a very annoying problem with it.
Ive hooked up a led on the front panel to show the status of the DIR1703's UNLOCK pin (lit when recieving SPDIF data).

Every time there is some small disturbance in this rooms power supply (a light turning on, heater thermo turning on/off, turning the soldering iron on/off, etc), the UNLOCK led will go out for about 1sec (DAC stops working) and then continue like normal.

ATM im using the PCM2902 (USB "soundcard" IC) which then feeds the SPDIF signal directly to the DIR1703.

Anyone come across this problem before?

Thanks.

Hi

Did you use an input transformer for SPDIF ? If so, the ground of the RCA / BNC input (SPDIF) should be galvanically connected to the chassis you build the DAC on

It is very likely to be a Common Mode problem inducing noise currents in the SPDIF interconect

regards
__________________
Guido Tent
www.Tentlabs.com
  Reply With Quote
Old 16th September 2003, 05:15 PM   #9
MWP is offline MWP  Australia
diyAudio Member
 
Join Date: Oct 2002
Location: Adelaide, South Australia
Default Re: Re: DAC interference problems

Quote:
Originally posted by Guido Tent

Did you use an input transformer for SPDIF ? If so, the ground of the RCA / BNC input (SPDIF) should be galvanically connected to the chassis you build the DAC on

It is very likely to be a Common Mode problem inducing noise currents in the SPDIF interconect
Hmmm, ok thanks, makes sense.
Im not using a input transformer... i have no idea where to get one from

Ive switched over to optical SPDIF between the PC and the DAC now anyway, so the problem is gone.

But ill fix it anyway since it has the USB and Coax SPDIF ports on the back of the DAC that can still be used.
  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
GSM interference watermelonman Tubes / Valves 9 25th October 2008 07:01 PM
Really bad interference... how to fix? dxg Everything Else 11 14th November 2005 01:48 PM
FM interference with AR sub mashaffer Subwoofers 0 21st July 2005 12:31 PM
Interference Prune Everything Else 1 22nd September 2003 04:37 PM


New To Site? Need Help?

All times are GMT. The time now is 04:48 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