Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

Rebuilding my 2011 LM3886, question about grounding (or lack thereof...)
Rebuilding my 2011 LM3886, question about grounding (or lack thereof...)
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 17th October 2018, 03:39 PM   #1
lost eden is offline lost eden  United Kingdom
diyAudio Member
 
Join Date: Sep 2009
Default Rebuilding my 2011 LM3886, question about grounding (or lack thereof...)

Back in 2011 I successfully built myself a pair of LM3886 amplifiers using amp PCBs from Analog Metric & power supply boards made from perfboard/stripboard. I have been using this setup pretty much daily for 7+ years with zero issues. In fact not only do they sound great, but they quite possibly have the lowest amount of background hum/hiss/noise of any amplifier I have ever owned. The construction is very basic, as seen in this diagram which essentially shows every single wire, with nothing omitted for brevity.

2011_gainclone.png

I am about to embark upon a new project, where I will essentially rebuild this two-channel setup into a 3-channel 2.1 setup. Both of the current amp boards will be powered from one of the current transformer/power supply boards (for the L/R speakers), the now spare transformer/power supply board will be used to power a new 2x LM3886 (parallel) board (for the sub) & a new small transformer/power supply board will be added to power a new 2.1 crossover board.

2018_gainclone.png

I am aware that 76V is towards the high side for LM3886 (this was due to my inexperience, not realising that the transformers I bought were spec'd with 230V primaries while my AC usually runs 245-247V), but as the current two-channel setup has been running just fine like that since 2011 I don't intend to spend money on new transformers or regulators.

So my actual question is about grounding. Since completing the original two-channel setup, I have come across a vast number of very long Website articles, forum threads, etc. discussing different grounding techniques (star ground, bus ground, etc.). However my setup in its current two-channel state seems to ignore all of that. Taking into account the fact that it has been working flawlessly since 2011, what is wrong with the grounding of my current two-channel setup (both in terms of quality/performance & in terms of safety) that I should change for the new three-channel setup?

Last edited by lost eden; 17th October 2018 at 03:42 PM. Reason: spelling
  Reply With Quote
Old 17th October 2018, 06:43 PM   #2
aparatusonitus is offline aparatusonitus  Croatia
diyAudio Member
 
aparatusonitus's Avatar
 
Join Date: Jan 2004
Location: Split, Croatia
Quote:
Originally Posted by lost eden View Post
what is wrong with the grounding of my current two-channel setup (both in terms of quality/performance & in terms of safety) that I should change for the new three-channel setup?[/B]
Nothing...as long as you use separate power supply for each amplifier. The moment you connect two amplifiers to one power supply you will get ground loop problem(s). A quick and easy solution (without much digging on pcb) is to separate the signal ground from power ground on the pcb board of each left/right amplifier with 10 Ohm resistor. In any case, the best solution is to make a new power supply for the subwoofer channel (with proper VDC over LM3886 this time).
__________________
Non mai abbastanza...
  Reply With Quote
Old 17th October 2018, 09:29 PM   #3
lost eden is offline lost eden  United Kingdom
diyAudio Member
 
Join Date: Sep 2009
So are the complex grounding techniques I see in so many LM3886 builds (like the attached pictures) only applicable for builds that run multiple separate amplifier boards from a single shared power supply?

If that is correct, I think I will wait for my new case to arrive & see if it is large enough to fit a third big transformer in the front for the sub amplifier... Because it seems like a much simpler, cleaner & more straight-forward approach to building? The total weight will be over 12kg but that doesn't concern me, as the current setup fills an entire 6U rack & this new build will be a single 2U case...
Attached Images
File Type: png gain-clone-earths.png (116.7 KB, 153 views)
File Type: jpg 2016-02-01-11.jpg (245.2 KB, 156 views)
File Type: jpg 2016-02-01-08.jpg (184.8 KB, 150 views)
  Reply With Quote
Old 17th October 2018, 10:36 PM   #4
scottjoplin is offline scottjoplin  Wales
diyAudio Member
 
scottjoplin's Avatar
 
Join Date: Dec 2015
Location: Penrhyndeudraeth
It means you won't have any cross channel ground loops. There could be others, but they are simpler to remedy
__________________
Woofer Assisted Wideband is the New Testament renounce the anachronistic acronym FAST
  Reply With Quote
Old 22nd October 2018, 12:12 AM   #5
tomchr is offline tomchr  Canada
diyAudio Member
 
tomchr's Avatar
 
Join Date: Feb 2009
Location: Calgary
My take on the matter: LM3886 chip amp grounding.

Tom
__________________
Modulus-86, 186, 286, & 686: 40-240W (8Ω) at <-120dB THD. HP-1: 3W/20Ω, -130dB THD, 128dB DNR.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
  Reply With Quote

Reply


Rebuilding my 2011 LM3886, question about grounding (or lack thereof...)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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Another Lm3886 grounding question... Drummer 35 Chip Amps 7 26th July 2017 07:08 PM
Can lack of grounding cause shut-offs? strannik Solid State 14 26th May 2017 01:14 PM
LM3886 Grounding Question aoeuhtns Chip Amps 31 6th March 2014 03:25 PM
Lack of bass with LM3886 maillard Chip Amps 40 18th February 2013 10:13 PM
Cabinet grounding/bonding - or lack thereof stellavox Construction Tips 1 26th January 2013 01:25 PM


New To Site? Need Help?

All times are GMT. The time now is 08:43 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki