Chip amp power supply- a beginners guide - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 23rd August 2008, 11:00 AM   #1
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Default Chip amp power supply- a beginners guide

Following on from some of the discussion on this forum about building chip amp power supplies, I am pleased to announce the addition of another page to the Gainclone section at Decibel Dungeon. I hope that it will answer many of the typical power supply questions that regularly crop up here.

I have tried to explain things both simply and comprehensively but most importantly, I have focussed on the safety aspects of building a mains fed power supply. I sincerely hope that all chip amp builders will make use of this resource and that it will keep them, and their property safe.

If you think that there is anything to add to the guide, or anything that isn't explained clearly enough, please use this thread to point that out, and I will make the necessary amendments.

A big thank you to AndrewT who took time off from his dancing) to proof-read the guide, and suggest corrections and additions.

You can find the guide here .
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.

Last edited by Pano; 6th October 2012 at 04:24 PM. Reason: link updated
  Reply With Quote
Old 5th September 2008, 01:33 PM   #2
kanifee is offline kanifee  United Kingdom
diyAudio Member
 
Join Date: Apr 2008
WOW! great tut nuuk, it really helped me with discrete diodes and bridge rectifiers. best of it is its rite in time for me to build my PSU for my bridged gainclone. One question i think i always get mixed with, a transformer wired with twin secondary's has a positive and negative rail, when its wired as a center tapped trafo does it still have a positive and negative rail along with a ground or is a say +25 0v(ground) +25. i only ask as buiding my bridged lm3886 i need to fit the terminals and noticed the LM3886 has +v +v -v and ground pins. my first thought was, +v -v and ground were what i used to connect to the psu but now im questioning my self. admitidly i should post this in the chip amp section but the problem has just arised and reading this tut i feel more \might ask similerl so it seems like the rite place.

Once again great tut!
  Reply With Quote
Old 5th September 2008, 01:46 PM   #3
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
No transformer has positive or negative outputs. It is all AC until after the bridge rectifier(s).

If you have a centre-tapped traffo, you can (only) feed one bridge and you get a single positive and a single negative rail out of that. By referencing those rails to the centre tap you get your +/- voltages.

If your transformer has twin secondary windings, you can use two bridges, have two sets of positive/minus rails, and the zero volt rail is the junction between the negative or one, and the positive of the other (as in the diagram below)

Click the image to open in full size.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 5th September 2008, 03:05 PM   #4
diyAudio Member
 
Greg Erskine's Avatar
 
Join Date: Jan 2002
Location: Sydney/Australia
Nice work Nuuk, that must have taken some effort.

BTW: Rod Elliott has 2 t's

regards
__________________
Greg Erskine
  Reply With Quote
Old 5th September 2008, 03:29 PM   #5
diyAudio Member
 
Join Date: Aug 2008
Just in time for me too as I'm starting my PSU today or tomorrow.

The only thing that didn't make sense is use of the lightbulb protection... specifically, wouldn't you test with the 40W, then the 60W, then the 100W, THEN use the bulb bypass switch?
  Reply With Quote
Old 5th September 2008, 03:38 PM   #6
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Quote:
BTW: Rod Elliott has 2 t's
Better change that then Greg. I don't want to upset Rod!

Quote:
The only thing that didn't make sense is use of the light bulb protection... specifically, wouldn't you test with the 40W, then the 60W, then the 100W, THEN use the bulb bypass switch?
I'll let Andrew answer that one Redshift, and then update the guide if necessary.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 5th September 2008, 07:52 PM   #7
kanifee is offline kanifee  United Kingdom
diyAudio Member
 
Join Date: Apr 2008
one more thing about cap orientation on these + and minus rails of the psu, on the plus side obviously the positive pin of the cap is on th e positive rail and negative on the ground, on the negative rail is this the same case or does the negative leg go on the -v rail and positive leg on the ground like this?

Click the image to open in full size.

or am i just being silly!
  Reply With Quote
Old 5th September 2008, 08:15 PM   #8
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Think of the voltage rails being rungs of a ladder.

The positive rail is the highest, the zero volt rail is in the middle, and the negative voltage is the lowest rung.

And the rule is, the positive side of the cap always goes to the higher rung of the ladder.

Another way to think of it is 0 is higher than any minus figure.

So yes, your diagram is correct (and it wasn't a silly question).
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 5th September 2008, 09:01 PM   #9
kanifee is offline kanifee  United Kingdom
diyAudio Member
 
Join Date: Apr 2008
Great analogy, itj ust seemed a little daft when i went over it in my head but the way you put it across was spot on!!!
  Reply With Quote
Old 5th September 2008, 09:07 PM   #10
! is offline !  United States
diyAudio Member
 
Join Date: Jun 2005
Location: Midwest
Nice job on the article but I would have to disagree with the following sentence in it, or possibly only the way it is worded:

Quote:
I suggest the following arrangement. About 10-100 uF after the bridge rectifier, and 1000 uF on each pin of the chip amp
Generally the most capacitance should come immediately after the bridge rectifier with the 10-100uF on each power pin of the chip amp. Whether or not this has as much *magic* depends a lot on the source and speakers. When either of those color the sound it can mean doing odder things to the amp but I would rather have a tonnally & detail accurate amp and replace the parts with a problem instead.
  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
A Beginners Guide to Enclosure Alterations Bork Multi-Way 7 12th January 2009 03:10 AM
beginners ecl82 power supply emil_86 Tubes / Valves 15 25th September 2004 06:20 AM


New To Site? Need Help?

All times are GMT. The time now is 08:15 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