Go Back   Home > Forums > Amplifiers > Power Supplies

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 11th January 2013, 11:46 AM   #5661
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
P.S. Why such a big cap? Needing absolutely minimal 1/F noise between 0-10Hz for digital clock and such?
  Reply With Quote
Old 11th January 2013, 11:48 AM   #5662
roender is offline roender  Romania
diyAudio Member
 
roender's Avatar
 
Join Date: Sep 2006
Quote:
Originally Posted by Salas View Post
Not really with such a big cap swamping it, if you mean connected like in the attached clip.
Exactly!
Thanks.
I have to confess that a very big reference capacitor, especially one with very low ESR, is a plus for regulator audio signature.
I used with success on that position 2200uF Panasonic FC. The regulator is used for a preamplifier with very poor power supply rejection.
  Reply With Quote
Old 11th January 2013, 11:54 AM   #5663
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Such an enormous cap brings down the ref impedance a lot but it would certainly kick back hard, no doubt protection is a must. How did you manage a good layout with such a monster? Put underneath?
  Reply With Quote
Old 11th January 2013, 11:57 AM   #5664
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Ah, sorry, not 22000, 2200. I read it too fast. Should be no more than 22mm D if 25V.
  Reply With Quote
Old 11th January 2013, 11:59 AM   #5665
roender is offline roender  Romania
diyAudio Member
 
roender's Avatar
 
Join Date: Sep 2006
Thanks to a very permissive PCB design, it fits without any problem on the BiB board :-)
  Reply With Quote
Old 16th January 2013, 05:27 AM   #5666
diyAudio Member
 
Join Date: Oct 2009
Location: Brunei
Guys, i have searched the thread but did not find an answer.

I am at the optimization stage of my dac and thinking of tackling power supply impedance to the tda1541 and clock. Unfortuntely i am not in a position to measure output impedance in circuit (no money for a network analyzer).

So second best is simulations....I have seen the output impedance models posted over the years. However has anyone ever posted some info on optimizing the output impedance of the reg in conjunction with one or more decoupling caps? In digital we are looking at as low as possible into the >10mhz range..... Are there any tried recipes out there?
__________________
--------
TDA1541a-S2 / 6072a / MediaplayerDac -- Michell Gyrodec -- Aikido Preamp -- Pass F5 -- Audio Physic Tempo 2SE -- Yamamura Cabling
  Reply With Quote
Old 16th January 2013, 06:15 AM   #5667
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Track inductance, shielding, local decoupling, and layout are the catches at such frequencies, only RF engineering will answer there.
  Reply With Quote
Old 16th January 2013, 07:04 AM   #5668
gootee is offline gootee  United States
diyAudio Member
 
Join Date: Nov 2006
Location: Indiana
Blog Entries: 1
Quote:
Originally Posted by studiostevus View Post
Guys, i have searched the thread but did not find an answer.

I am at the optimization stage of my dac and thinking of tackling power supply impedance to the tda1541 and clock. Unfortuntely i am not in a position to measure output impedance in circuit (no money for a network analyzer).

So second best is simulations....I have seen the output impedance models posted over the years. However has anyone ever posted some info on optimizing the output impedance of the reg in conjunction with one or more decoupling caps? In digital we are looking at as low as possible into the >10mhz range..... Are there any tried recipes out there?
You need to have an array of many caps, on a two-sided PCB with unbroken planes of copper on both sides (drill holes only, with denuded hole edges on one side of pcb, for cap leads). You'll have one of those as each power rail. They need to be shaped right, not long and narrow.

With a 10x10 array of 1000 uF electrolytics, and a 1mm thick FR4 board, you should be able to get the total inductance seen at the load down to less than 1 nH; probably to 0.5 nH.

You might want to use a daughterboard for your main circuit, with standoffs so it is straddling over the edge(s) of the cap array board(s) (depending on whether you need dual-polarity supply), so that all of the power and ground pins can go straight down through the duaghterboard and directly into the cap array board(s). [Or, of course, use a real multi-layer board, with caps distributed all over the board, and power and ground feeds distributed all around their layers.]

The illustrious Terry Given, electromagneticist extraordinaire, presented a prototype, with actual network analyzer measurements, and design guidelines, right here on diyaudio (His was for power amps. Maybe you can re-size caps as needed.).

I created a set of links directly to his posts about it, so people wouldn't have to search for them individually, and wouldn't miss any, which I put at the bottom of the post at:

LM3886 component selection

NOTE that in the first link, Terry meant to say RADIAL instead of AXIAL.

P.S. Also do a google search for papers and webpages by Henry W, Ott, Bruce Archambeault, Eric Bogatin, and others.

P.P.S. There are much-cheaper but more-labor-intensive ways to measure impedance, than a network analyzer.

Enjoy,

Tom

Last edited by gootee; 16th January 2013 at 07:23 AM.
  Reply With Quote
Old 16th January 2013, 03:26 PM   #5669
diyAudio Member
 
Triodethom's Avatar
 
Join Date: Dec 2009
Location: Newnan GA
Hi Salas I have a st-1700a distortion meter. It has a 15volt plus/minus supply for each of the section osc. and detector . the raw voltage before the regs is about 35 volts+/- each rail . If I use your regs should I pre reg the voltage down to what ? Thanks for your view .
  Reply With Quote
Old 16th January 2013, 04:49 PM   #5670
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Just use CRC down to 25V DC. If its not constant draw, avoid 317,337, better use Zeners.
  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



New To Site? Need Help?

All times are GMT. The time now is 07:49 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