LM3886, power caps, input resistors, mute, and Cm. - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 20th December 2007, 07:17 PM   #1
mudihan is offline mudihan  United States
diyAudio Member
Join Date: Jan 2004
Location: Texas
Default LM3886, power caps, input resistors, mute, and Cm.

Just got BrianGT's kit, and have a few questions:

On the amp board:
1) Would it be better to put R2 (signal to ground) before R1 (switch the positions)? Also, should the value of R2 be 10x of the value of the pot before it (i.e., 10k pot with 100k R2, followed by the original 1k R1)?

2) Would it be a good idea to put a 10000uf TS-UP +a 100uf FC + a 15uf Tantalum + a 0.1uf Film on each rail next to the chip. The TS-UP will further take care of ripple (after the 10000uf ones in the power supply section), the FC will charge faster, the tan will absorb low frequency variations (suggested by the datasheet), and the film will do the high frequency. --- I just have extra 10000uf TS-UP and 15uf Tans laying around.

3) Mute -- does this function degrade sound in any way? If it does, to disable it, would a 1/8w 10k resistor between Pin 8 and ground be enough (or will it get burned)?

4) The feedback caps Cm -- what is the lowest voltage requirement for those? I have 25v 47uf Silmic II laying around.

Many Thanks!
  Reply With Quote
Old 20th December 2007, 09:29 PM   #2
diyAudio Member
Join Date: Apr 2006
Location: live in mountains
Cm is 100f/50V

Ci is 47f/50v

for the minimum rails voltage

tell us which toroids (18v,22v or 25v)you use and which speakers (4ohms or 8ohms )

  Reply With Quote
Old 21st December 2007, 01:32 AM   #3
mudihan is offline mudihan  United States
diyAudio Member
Join Date: Jan 2004
Location: Texas
I am using a 22VACx2 transformer, with 32vdc at the output of the power supply board. Driving 8ohm speakers (NHT acoustic suspension type) with around 86db sensitivities.

Is R2 (22k input to ground) really necessary if I put a 10k ladder-type stepped pot before R1?
  Reply With Quote
Old 21st December 2007, 09:23 AM   #4
AndrewT is offline AndrewT  Scotland
diyAudio Member
Join Date: Jul 2004
Location: Scottish Borders
you must activate the mute pin. It won't amplify otherwise.
regards Andrew T.
Sent from my desktop computer using a keyboard
  Reply With Quote


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
LM3886 Mute Disable mothman Chip Amps 15 28th January 2013 05:05 AM
lm3886 no mute rtill Chip Amps 21 29th August 2009 05:43 AM
LM3886: Mute Capacitor Cm mudihan Chip Amps 1 24th July 2008 02:48 AM
LM3886 Mute richie00boy Chip Amps 6 18th August 2004 11:26 AM
lm3886 mute LED blabley Solid State 1 30th May 2002 05:51 AM

New To Site? Need Help?

All times are GMT. The time now is 03:23 PM.

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