LM3886 noise when turn on the light switch - 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 1st May 2011, 03:16 AM   #1
diyAudio Member
 
Join Date: Oct 2010
Location: Taipei
Default LM3886 noise when turn on the light switch

This is first post, I built a dual mono LM3886 with two 300VA transformer and 10000uf/63v cap per rail, the sould is pretty good overall, but everytime when someone mechanical turn on or turn off the light power and sometimes the Refrigerator Compressor also influence , my speaker will have "pia" noise, but this situation not happened for my previous power amp, except this the background is very silence, is anyone experience for this , thanks.
  Reply With Quote
Old 1st May 2011, 04:22 AM   #2
infinia is offline infinia  United States
diyAudio Member
 
infinia's Avatar
 
Join Date: May 2005
Location: Californication
probably RFI interference ( spark gap transmitter)

Do more trouble shooting to discount other connections or gear / music sources.
show us your build for better advice
RF filters on audio input and/or on power entry
shielding enclosure
twisting wires to reduce pick up
__________________
like four million tons of hydrogen exploding on the sun
like the whisper of the termites building castles in the dust

Last edited by infinia; 1st May 2011 at 04:26 AM.
  Reply With Quote
Old 1st May 2011, 04:33 AM   #3
6L6 is online now 6L6  United States
diyAudio Member
 
6L6's Avatar
 
Join Date: Oct 2010
Location: Denver, Colorado
Do you have 2.2uf DC-blocking cap on the input? If no, try it, that may solve your problem.
  Reply With Quote
Old 1st May 2011, 01:21 PM   #4
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
RF attenuation is required.
Unfortunately National do not show RF attenuation as compulsory in their datasheets and even show example schematic with no RF attenuation for the mains cables nor for the inputs.
__________________
regards Andrew T.
  Reply With Quote
Old 1st May 2011, 10:48 PM   #5
diyAudio Member
 
Join Date: Oct 2010
Location: Taipei
Many thanks you guys suggestion, I will try the RF filter at input RCA socket, but any recommend for the value? how about 680 ohm +470pF
  Reply With Quote
Old 1st May 2011, 11:43 PM   #6
diyAudio Member
 
ByronInPortland's Avatar
 
Join Date: Nov 2010
Location: Portland, Oregon
The noise may also be coming from your ground. I'm assuming your amp has a safety ground going to the wall outlet. Your refrigerator may be injecting noise into your building's ground wiring, which is finding its way into your amp. Fortunately, there is a rather nice article on this web site which deals with this problem. Here is the link:
Audio Component Grounding and Interconnection
Chapter 2 deals, specifically with the problem of noise.

Good luck!
  Reply With Quote
Old 2nd May 2011, 02:20 AM   #7
diyAudio Member
 
Join Date: Oct 2010
Location: Taipei
Actually I tried many power amp(none chip), only this Lm3886 have this problem, so I think may be the chip amp is more sensitive for power or environment, next action maybe I will add a regulated power supply(use LT1083), I have no idea is this work?
  Reply With Quote
Old 2nd May 2011, 09:26 AM   #8
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Don't regulate.

Attenuate the interference.

Fit an RF filter at the input of the chipamp.
Consider adding a filter direct across the RCA input sockets.

Fit mains filter. They are available ready built as IEC sockets with all the correct components inside. Obtain the lowest current rating that will safely power your equipment. They are usually available in 1A, or 3A, or 6A

A metal chassis completely enclosing your amplifier also attenuates interference, especially if you have unattenuated emissions coming from radios and motors around the house.

It is always better to attenuate interference at source. Move the mobile radio, the wireless alarm system, the wireless doorbell, the wireless computer network, etc.

Fit all motors especially and switches in general with a snubbing network. These too are available ready assembled.
__________________
regards Andrew T.
  Reply With Quote
Old 3rd May 2011, 09:37 AM   #9
diyAudio Member
 
Join Date: Oct 2010
Location: Taipei
Thanks all of your comments, I prepared the parts for RC filter will install tonight, I will update the result.
  Reply With Quote
Old 4th May 2011, 02:58 AM   #10
diyAudio Member
 
Join Date: Oct 2010
Location: Taipei
I add the RC filter, but doesn't work, attached the schematic, any ideas?

R1:22K
R2:22K
R3:1K
R4:22K
R5:1K
C1:100uf/35v
C2:100uf/35v
C3:100uf/35v
C4:22uf/35v
C5:1uf
Attached Images
File Type: jpg Lm3886.jpg (11.8 KB, 167 views)
  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
Capacitor Across Power Switch to Control Switch On Noise? DreadPirate Analog Line Level 20 21st April 2013 02:58 PM
Install a switch to prevent turn on hum xecluded Chip Amps 7 12th March 2010 07:37 AM
Eliminate influence of switching noise from light switch in to power supply artquake Power Supplies 34 20th October 2008 05:09 PM
How can I reduce mechanical turn on and turn off noise? soundNERD Chip Amps 8 28th October 2003 01:43 AM
turn on noise junglejuice Solid State 5 27th October 2002 06:49 AM


New To Site? Need Help?

All times are GMT. The time now is 08:59 PM.


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