SMPS _ shielding options. - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts 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
Reply
 
Thread Tools Search this Thread
Old 14th May 2016, 08:56 AM   #1
diyAudio Member
 
Join Date: Sep 2009
Location: Stavanger (NORWAY)
Default SMPS _ shielding options.

Hi !
i have an audio interface here that has a noise issue.
And actually a guy with the same unit, after measuring this noise, has pulled out the smps from the case and the noise has gone away.
The ripple from the smps instead is nicely low and absolutely acceptable.
Therefore it seems clear that the noise originates from an imperfect shielding of the smps.
I am attaching picture of the smps.
I wonder if there is a way to spot the part who is generating this issue and add some shielding to tame this noise.
Another solution would be to extract the smps but that complicates the unit.
Moreover i see a multiwire connector going to the pcb with circuits.
So replacing this smps with a linear (may 1st idea) without having the schema could be difficult.
Advice are very welcome and appreciated.
Thanks a lot indeed.
Regards, gino
Attached Images
File Type: jpg barrier.jpg (639.1 KB, 376 views)
File Type: jpg connector.jpg (560.8 KB, 365 views)
File Type: jpg smps full pic.jpg (391.1 KB, 346 views)
File Type: jpg smps.jpg (749.9 KB, 337 views)

Last edited by ginetto61; 14th May 2016 at 09:01 AM.
  Reply With Quote
Old 14th May 2016, 09:16 AM   #2
diyAudio Member
 
JonSnell Electronic's Avatar
 
Join Date: Dec 2012
Location: The Jurassic Coast, England. GB
If you contact TEAC and this is an issue, they will advise accordingly.
__________________
Support for Fender, Marshall and all Valve Equipment; Audio Innovations, Audiorama FU29, Quad and Leak. www.jonsnell.co.uk
  Reply With Quote
Old 14th May 2016, 09:32 AM   #3
diyAudio Member
 
Join Date: Sep 2009
Location: Stavanger (NORWAY)
Quote:
Originally Posted by JonSnell Electronic View Post
If you contact TEAC and this is an issue, they will advise accordingly.
Hi ! thanks for the reply.
Someone else has already contacted Teac and they say that this is a marginal issue not impacting the functioning of the unit.
And actually the unit works. Not very classy answer by the way.
Maybe because this is a cheap unit and cannot be perfect.
It would create problem to more expensive ones.
Poor people must suffer ...

However the interesting part is that if there were a dc socket on the unit a decent external smps could have solved elegantly the issue.
I am re-evalueting the classic wall adapters a lot.
The guy tried a 12VDC smps from Seasonic with very good results in terms of residual ripple.
A 20-25 USD piece and a dc socket would have solved the issue completely.
And the unit could have been much smaller too (who design these units ?).
Then one would be free to use the power supply of choice.
I would do the mod myself but without schematic of the power supply the risk is huge.
I do not want to fry the unit.
I love external power supplies immensely.
And in general power supplies are the component that fascinates me more. More than anything else.
Kind regards, gino

Last edited by ginetto61; 14th May 2016 at 10:00 AM.
  Reply With Quote
Old 14th May 2016, 10:21 AM   #4
diyAudio Member
 
fabrice63's Avatar
 
Join Date: May 2015
Location: Fréjus
are you sure your smps gives you only 12 DC ?

it looks like multiple voltage output , a DC and a symmetrical +/- .

what TEAC device is that ?

.
  Reply With Quote
Old 14th May 2016, 10:33 AM   #5
diyAudio Member
 
Join Date: Sep 2009
Location: Stavanger (NORWAY)
Quote:
Originally Posted by fabrice63 View Post
are you sure your smps gives you only 12 DC ?
it looks like multiple voltage output , a DC and a symmetrical +/-
Hi ! no i am not sure.
I am a little scared about pull it out and measure. I understand there is high VAC involved.
The guy said 11.2 VDC and some of the connectors are linked together.
So i guess a single V out power supply can be used because it is what he did.
I will try to extract the animal ...
I would really like the dc socket option on the back.
Or another option could be going with AC to the unit and place a regulation stage inside. Nice and clean. With the polluting mains transformer out of the case. What puzzles me is they do almost everything very well and then skip on the last details that would make the product almost perfect. For nothing more.

Quote:
what TEAC device is that ?
Product: UH-7000 | TASCAM

Regards, gino

Last edited by ginetto61; 14th May 2016 at 10:37 AM.
  Reply With Quote
Old 14th May 2016, 08:00 PM   #6
Pafi is offline Pafi  Hungary
diyAudio Member
 
Join Date: May 2004
Location: Budapest
It seems to be a simple fly-back SMPS. They are simple, and easy to controll, but generates very high level of capacitive disturbance. There is a common mode choke to attenuate this, but not surprisingly its not enough. Since moving away the psu helps, the conductive coupling is managed well, but very probably stray capacitance injects noise to everywhere. You can shield transformer and primary sides witcher, but special care is needed to preserve isolation strength, especially since the shielding must be connected to output GND. Maybe through a Y capacitor.
  Reply With Quote
Old 14th May 2016, 09:52 PM   #7
dmills is offline dmills  United Kingdom
diyAudio Member
 
Join Date: Aug 2008
Location: High Wycombe
I would not be surprised to find a +48V rail on these as well as whatever the notional rails are (+,-15V to 18 or so), or maybe a logic supply if the phantom is generated on board.

I do not believe this to be a single +12V rail.

Regards, Dan.
  Reply With Quote
Old 15th May 2016, 07:23 AM   #8
diyAudio Member
 
Join Date: Sep 2009
Location: Stavanger (NORWAY)
Quote:
Originally Posted by Pafi View Post
It seems to be a simple fly-back SMPS.
Hi ! thanks a lot for the very helpful reply.
Before continuing there is an update. I checked the partition between the smps and the circuits board ... it is just a very thing sheet of plastic
The other partitions i have seen they were all metallic.
I wonder what level of shielding a platic partition can provide, if any ...
I really would like to try something more effective.

Quote:
They are simple, and easy to controll, but generates very high level of capacitive disturbance. There is a common mode choke to attenuate this, but not surprisingly its not enough.
Since moving away the psu helps, the conductive coupling is managed well, but very probably stray capacitance injects noise to everywhere. You can shield transformer and primary sides witcher, but special care is needed to preserve isolation strength, especially since the shielding must be connected to output GND. Maybe through a Y capacitor.
Thanks a lot again for the very kind advice.
I think i could do much more harm than good.
I see that other interfaces come with an external smps ... much more handy solution. In this way shielding is guaranteed.
I would like to extract the smps and put insted a linear regulation stage and using an external mains transformer.
Because from what i read this thing has a nice potential.
I hope some of the owners will pop up with a handy solution.
Strange that in Tascam has overlooked this issue. For them to solve it would have been trivial.
Thanks a lot again, gino
  Reply With Quote
Old 15th May 2016, 07:28 AM   #9
diyAudio Member
 
Join Date: Sep 2009
Location: Stavanger (NORWAY)
Quote:
Originally Posted by dmills View Post
I would not be surprised to find a +48V rail on these as well as whatever the notional rails are (+,-15V to 18 or so), or maybe a logic supply if the phantom is generated on board.
I do not believe this to be a single +12V rail.
Regards, Dan.
Hi Dan ! thanks a lot for the kind and valuable advice.
I can find only TEAC E90327-00C written on it.
I wonder if a service manual with schematic is available from any vendor to see the actual voltages generated.
As i said this interface as a high potential for good sound.
A low noise linear supply with the transformer kept external, would eliminate any issue of intereference.
The space available can accomodate easily a good quality regulation stage.
The circuit board is very well designed, someone says.
Next time i will buy one with external ac adapter for sure.
I like to play with power supplies a lot. It is the only way i can do.
Thanks a lot again, gino

Last edited by ginetto61; 15th May 2016 at 07:41 AM.
  Reply With Quote
Old 15th May 2016, 03:43 PM   #10
dmills is offline dmills  United Kingdom
diyAudio Member
 
Join Date: Aug 2008
Location: High Wycombe
Have you tried just measuring the rails, there are only 4 wires, so probably three rails (I would guess +-15 or so, and a low current +48 for the phantom supply) ?

Secondly, what measurements have you made to establish that the switcher is the problem, and that the problem is radiated emissions, IME the issue is at least as often conducted in the MHz region.

Contrary to popular belief it is entirely possible to design a mic preamp with a switcher for a supply and have the switcher be completely blameless, not that it is a given but it can be done.

Regards, Dan.
  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
Shielding ..... east electronics Solid State 9 20th July 2009 07:34 AM
Shielding? ROBSCIX Analog Line Level 7 27th October 2006 05:28 PM
Shielding Lostcause Everything Else 12 8th November 2005 02:30 PM
Shielding KornChild5 Everything Else 0 3rd May 2005 06:37 AM
Shielding peterr Everything Else 2 17th September 2002 11:57 AM


New To Site? Need Help?

All times are GMT. The time now is 07:46 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki