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

Bypassing pin question
Bypassing pin question
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 31st July 2012, 04:58 AM   #1
JamieB is offline JamieB  Australia
diyAudio Member
Join Date: Jul 2012
Default Bypassing pin question

I have just built my first stereo amplifier based on the typical applications circuits in the LM386 data sheets. It works very well so I'm happy.

However, the speakers I have it connected to sound a bit tinny and I want to compensate for the lack of bass so I'm looking at the bass boost circuit in the data sheet.

The data sheet refers to bypassing certain pins. Is this just a standard bypass running from the pin to a cap to ground? Also, I notice that the diagrams feature dotted lines running to a cap labelled "bypass". Is this standard practice for designating a bypass capacitor? I assume that a value of 0.1uF is a good value to use here?

  Reply With Quote
Old 31st July 2012, 07:07 AM   #2
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
Mooly's Avatar
Join Date: Sep 2007
Bypassing pin question
Hmm... the LM386. That's an oldie

For good bass response the speaker coupling cap needs to be large enough. That depends on the speaker impedance but 250uf and 8 ohm has a -3db point of around 80hz. So something of the order of 2200uf would be better.

The bypass pin (pin 7) I would have though would be decoupled with something around 10uf to ground.

The big problem with all these older IC's is that although they seem ultra simple to use they can in reality be prone to oscillation and instability. Layout has much to do with that. I would always recommend using a scope to check for stability. Manufacturers data sheets often show alternative parts as dotted. You have to remember these are typical applications rather than fully worked projects.
  Reply With Quote
Old 31st July 2012, 07:26 AM   #3
gmphadte is offline gmphadte  India
diyAudio Member
Join Date: Jul 2003
Location: Dona paula, Goa
There is a bass boost schematic on the datasheet. However with so low power, less than 1Watt, I doubt u will get anything. Go for some higher power ICs like TDA2003. And I hope your speakers are in a cabinet.

Gajanan Phadte
  Reply With Quote


Bypassing pin questionHide 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
pin count question gary h Tubes / Valves 7 16th June 2008 09:07 PM
DF1704 pin out question luvdunhill Digital Source 6 31st January 2008 05:11 PM
TDA1541A Pin connection question dsavitsk Digital Source 0 6th March 2006 09:56 PM
A 3-Pin Regulator Question saurus Solid State 3 27th October 2003 01:54 PM
new gaincloner- question about bypassing Mel Chip Amps 11 23rd July 2003 11:57 AM

New To Site? Need Help?

All times are GMT. The time now is 01:55 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio