Chip amp power supply- a beginners guide - Page 34 - 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 19th May 2009, 03:48 PM   #331
diyAudio Member
 
jmillerdoc's Avatar
 
Join Date: Mar 2009
Location: Lawton, OK, USA
Default Parts suppliers?

I have recently started building Chip amps and found a very nice EI trafo that came out of a Parasound amp that blew up. I have been studying the various regulated schemata floating around on this forum and have decided to build a regulated PSU using this trafo. It is a 29.5-0-29.5 trafo so really I can probably use it without a regulated PSU but I want to try one. I like the design found at DOGBREATH.DE but I have one problem.....finding a parts supplier for these parts. Can anybody point me in the right direction in finding 2, 5, 10 watt wirewound resistors and the LM338? I found the LM338 at Farnell.com but there are x2 different ones with different specs...one with a 35v max input voltage and the other with 40v. ????? to use ????? Anyway, if anybody out there can help or, if anybody has a few of these parts to build one regulated PSU I would purchase them from you.
Thanks alot y'all,
Jeff Miller
Lawton, USA
millerjeff@ccmhonline.com
  Reply With Quote
Old 19th May 2009, 04:02 PM   #332
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Your traffo is going to put out around 42 volts after the rectifier bridges!

I think that the figures you are referring to for the LM338 are for Input Output Voltage Differential, that is the difference between the input voltage and the output voltage, rather than the maximum input voltage.

So you could use your traffo for a regulated supply down to around 7 volts although you obviously don't need to go that low for a GC.

Farnell sell the wirewound resistors that you talk about .
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 19th May 2009, 04:08 PM   #333
diyAudio Member
 
Join Date: Jun 2006
Location: Columbia, MO
Jeff,
That transformer will give about 41 volts DC which is way too high for a chipamp. Of course you could regulate it down but that will be a lot of power turned into heat unless you use a very sophisticated switched regulation system that will probably be too expensive. Good luck
Ted
  Reply With Quote
Old 19th May 2009, 04:13 PM   #334
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
your 29.5Vac transformer could charge the smoothing caps to about 46Vdc when very lightly loaded and mains is 6% high.
Don't think about using a 36 or 40V rated regulator.
__________________
regards Andrew T.
  Reply With Quote
Old 20th May 2009, 03:58 AM   #335
diyAudio Member
 
jmillerdoc's Avatar
 
Join Date: Mar 2009
Location: Lawton, OK, USA
Default 29.5v trafo

I thought the maximum input voltage for the LM3886 was 42v. I have tested my trafo on the rectifier and with the diode drop it measures exactly 40v DC. Couldn't I just use this in an unregulated fashion with the LM3886? I have built one with a 38.5v DC unreg supply without problems. What's another 1.5v? Is there an easy way to shave a couple of volts off the rails, maybe a resistor in parallel and series on the leads? I remember reading somewhere, I think in the art of electronics a way to create a voltage drop by putting a resistor in parallel and series on one of the leads but I don't remember the details of this. Any thoughts?
  Reply With Quote
Old 20th May 2009, 09:30 AM   #336
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Default Re: 29.5v trafo

Quote:
Originally posted by jmillerdoc
I have tested my trafo on the rectifier and with the diode drop it measures exactly 40v DC.
and what was the mains voltage when you carried out this test?

First impression is that is is NOT a 29.5Vac transformer.

Feed the computers with nonsense and they spit out nonsense in return.
__________________
regards Andrew T.
  Reply With Quote
Old 20th May 2009, 09:35 AM   #337
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
The maximum voltages for the 3886 are 94Vdc and 84Vdc.
See absolute maximum ratings.

What is your maximum voltage from your supplier?
Write or phone and ask them directly.

Then, find out the maximum voltage that the transformer will charge the smoothing caps to, to find if you can meet both conditional maxima.
__________________
regards Andrew T.
  Reply With Quote
Old 20th May 2009, 06:18 PM   #338
diyAudio Member
 
jmillerdoc's Avatar
 
Join Date: Mar 2009
Location: Lawton, OK, USA
Default BrianGT power supply

I have an extra PSU from a dual mono kit that I ended up not using in a dual mono config. Brians's PSU has x4 output leads a V-, PGND-, PGND+, and V+. I tried hooking the PGND's together to get a 35v(+) - 0 - 35(-) standard 3 power lead out configuration but when I did this it obviously begins to short out. Why can't I connect his PSU up this way? I was going to use this PSU in a point to point build, now I don't know what to do.
Any suggestions?
Jeff
  Reply With Quote
Old 20th May 2009, 06:19 PM   #339
diyAudio Member
 
jmillerdoc's Avatar
 
Join Date: Mar 2009
Location: Lawton, OK, USA
Default clarification

Sorry, I should clarify...the PSU above was one purchased from Chipamp.com....If you didn't already put that together.
Jeff
  Reply With Quote
Old 21st May 2009, 07:24 AM   #340
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Coupling the two separate PSUs together should work.
The amp PCB does the same thing, joins the two PNGD lines together, to create the zero volts reference and a dual polarity supply.

Go back and check your wiring.

To build two separate PSUs from a single transformer the transformer MUST HAVE dual secondaries. One cannot build separate PSUs from a centre tapped secondary.
__________________
regards Andrew T.
  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 02:10 AM
beginners ecl82 power supply emil_86 Tubes / Valves 15 25th September 2004 05:20 AM


New To Site? Need Help?

All times are GMT. The time now is 04:39 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