GND connections in an Amplifier using a transformer with two secondary windings - 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 24th September 2016, 07:42 PM   #1
diyAudio Member
 
Join Date: Aug 2016
Default GND connections in an Amplifier using a transformer with two secondary windings

Hi to everyone

Currently I am building a MOSFET Audio amplifier based on LME49830 chip from TI. The scheme consists:

POWER SUPPLY -> PRE-AMPLIFIER -> POWER AMPLIFIER -> LOAD (for each channel)

My power supple contains 2 PSU, the first one delivering +-60V to the POWER AMPLIFIER BOARD and the second one supplying +-12V to the PRE-AMPLIFIER board. In order to accomplish this, I ordered a costumed Transformer made for my requirements which consists on one primary winding and two secondary windings each one with a center tap (or mid-point).

The problem is that these mid-points are in different potential so I don't know if I can just connect them.

My POWER AMPLIFIER board also needs the +-12V supply in order to supply a current mirror I am using for a chip.

How would GND connections be in this case? I am asking because the output of the PRE-AMP board is referenced to the center tap of the 2nd secondary winding (+-12V) and this output goes to the POWER AMP board which GND is the center tap of the 1st secondary winding.

The potential between the two center taps is about 7Vrms (I measured it with a multimeter).

My idea is to use a very low resistor (and high power) between these 2 center taps but I also want to use a GND star configuration in order to avoid GND loops.

I'll appreciate any help from you guys.

Thanks!
Attached Images
File Type: png POWER AMPLIFIER BOARD.png (171.3 KB, 71 views)
File Type: png PRE AMPLIFIER BOARD.png (95.1 KB, 71 views)
  Reply With Quote
Old 24th September 2016, 08:13 PM   #2
diyAudio Member
 
JonSnell Electronic's Avatar
 
Join Date: Dec 2012
Location: The Jurassic Coast, England. GB
The mid points are your ground connection and usually are connected together giving you + - 12V and + - 60 volts.
__________________
Support for Fender, Marshall and all Valve Equipment; Audio Innovations, Audiorama FU29, Quad and Leak. www.jonsnell.co.uk
  Reply With Quote
Old 24th September 2016, 08:20 PM   #3
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Quote:
The potential between the two center taps is about 7Vrms (I measured it with a multimeter).
It is almost certain that you are not measuring what you think you are measuring.

Quote:
My idea is to use a very low resistor (and high power) between these 2 center taps but I also want to use a GND star configuration in order to avoid GND loops.
Correct. You should use a very low value resistor with high power handling - usually known as a piece of wire.

However, don't use the transformer CTs as the point of connection - this will guarantee buzz. Instead, connect each CT to its own reservoir capacitors junction, then connect the two junctions. This keeps charging currents out of the audio ground.
  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
Torodial transformer - help with secondary windings pvh1987 Power Supplies 2 2nd October 2011 06:45 PM
Shorted secondary windings of transformer Edvard Tubes / Valves 5 29th December 2010 10:22 PM
help: how to connect 2 pairs of secondary to +/gnd/- jtktam Power Supplies 3 27th January 2010 08:18 PM
transformer secondary connections jayme Tubes / Valves 0 4th October 2007 07:31 PM
Hammond Transformer Secondary Connections Mush Tubes / Valves 7 1st October 2007 08:13 PM


New To Site? Need Help?

All times are GMT. The time now is 06:06 AM.


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