lm1875 fizzing away probelm - Page 14 - 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
View Poll Results: Was a good idea to use two lm1875 or a big stk chip
Use stk 8 27.59%
use lm1875 21 72.41%
Voters: 29. You may not vote on this poll

Reply
 
Thread Tools Search this Thread
Old 19th January 2013, 07:31 PM   #131
blu_glo is offline blu_glo  England
diyAudio Member
 
blu_glo's Avatar
 
Join Date: Aug 2005
Location: London, England
Quote:
Originally Posted by PetruV View Post
Why is no one answering,why
- been busy helping others too!!
  Reply With Quote
Old 19th January 2013, 07:36 PM   #132
blu_glo is offline blu_glo  England
diyAudio Member
 
blu_glo's Avatar
 
Join Date: Aug 2005
Location: London, England
You might want to check against Fig.1 on P.4.....
Attached Files
File Type: pdf TDA2822M.pdf (364.1 KB, 14 views)

Last edited by blu_glo; 19th January 2013 at 07:50 PM.
  Reply With Quote
Old 19th January 2013, 07:37 PM   #133
PetruV is offline PetruV  Romania
diyAudio Member
 
Join Date: Dec 2012
Location: Bucuresti
Quote:
Originally Posted by blu_glo View Post
Which circuit did you follow?
Thanks for stopping by,the schematic is from datashee without zobel but i could not hear any high frequency oscilation while it was working
  Reply With Quote
Old 19th January 2013, 07:52 PM   #134
blu_glo is offline blu_glo  England
diyAudio Member
 
blu_glo's Avatar
 
Join Date: Aug 2005
Location: London, England
ummmm (hahaha) its usually either the supply rail needs a 10uF (maybe more say 100uF) capacitor across it or you've left the "unused" opamp input pins floating....

Last edited by blu_glo; 19th January 2013 at 08:20 PM.
  Reply With Quote
Old 19th January 2013, 08:00 PM   #135
blu_glo is offline blu_glo  England
diyAudio Member
 
blu_glo's Avatar
 
Join Date: Aug 2005
Location: London, England
Quote:
Originally Posted by PetruV View Post
Thanks for stopping by,the schematic is from datashee without zobel but i could not hear any high frequency oscilation while it was working
It is still a good idea, especially with "chip amps" to leave the specified Zobel network in. This is because like in the old days, the easiest way to get a power output stage in a chip is using NPN transistors only. You can see this if you look at P. 2 of the datasheet. The bottom transistor is working with it's collector going to the speaker. This is inherently problematic and can result in instability with open circuit or high impedance loads. The Zobel network helps keep things under control - so leave it out at your peril!!

BTW you are unlikely to *hear* the oscillation - it's clattering away at way beyond human hearing, - perhaps at a Mhz or so!! The normal giveaway (without resorting to an oscilloscope) is a very hot chip, even when it's doing nothing...


Last edited by blu_glo; 19th January 2013 at 08:16 PM.
  Reply With Quote
Old 19th January 2013, 08:15 PM   #136
PetruV is offline PetruV  Romania
diyAudio Member
 
Join Date: Dec 2012
Location: Bucuresti
Quote:
Originally Posted by blu_glo View Post
ummmm (hahaha) its usually either the supply rail needs a 10uF (maybe more say 100uF) capacitor accross it ir you've left the "unused" opamp input pins floating....
i have used 220uf on supply and havent left the pins floating i have them conected to ground trough 100 uf caps as in schematic,it previousely worked,but now it dosent work
  Reply With Quote
Old 19th January 2013, 08:23 PM   #137
blu_glo is offline blu_glo  England
diyAudio Member
 
blu_glo's Avatar
 
Join Date: Aug 2005
Location: London, England
Quote:
Originally Posted by PetruV View Post
i have used 220uf on supply and havent left the pins floating i have them conected to ground trough 100 uf caps as in schematic,it previousely worked,but now it dosent work
I think you need to look again at your wires and soldering - it feels like you've connected something and its disconnected since!
  Reply With Quote
Old 19th January 2013, 08:55 PM   #138
blu_glo is offline blu_glo  England
diyAudio Member
 
blu_glo's Avatar
 
Join Date: Aug 2005
Location: London, England
Since when in use on a computer soundcard AND its USB port the power is grounded in two places you could try (completely disconnected from computer of course!):

Disconnect the negative connections of C1 and C2 (fig. 1 of datasheet) from the board.
Join the two negative terminals of the capacitors together but not to 0V on the board.
Disconnect the screen of your left AND right inputs ( I presume this is coming from your soundcard line output) from the board and join it to the new junction of C1 and C2.

See if that improves matters!

Last edited by blu_glo; 19th January 2013 at 09:03 PM.
  Reply With Quote
Old 19th January 2013, 09:00 PM   #139
PetruV is offline PetruV  Romania
diyAudio Member
 
Join Date: Dec 2012
Location: Bucuresti
if i plug my radio in i get buzz just from oe chanell,not powered from laptop usb but from comp psu separate from audio source
  Reply With Quote
Old 19th January 2013, 09:10 PM   #140
blu_glo is offline blu_glo  England
diyAudio Member
 
blu_glo's Avatar
 
Join Date: Aug 2005
Location: London, England
It sounds like a ground is missing; in the stereo input plug perhaps?
  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
Hiss probelm on JLH class A rchung Solid State 8 8th January 2013 05:44 PM
Preamp for LM1875 tom91 Chip Amps 3 26th July 2009 04:08 PM
lm1875 siemensc65 Chip Amps 4 23rd May 2006 04:28 AM
Lm1875 soundNERD Chip Amps 14 12th October 2003 03:26 AM
offset probelm in bugle phono preamp dre Solid State 5 13th April 2003 07:41 PM


New To Site? Need Help?

All times are GMT. The time now is 11:39 AM.


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