LM3886 loud pop when turned off - Page 4 - 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 6th October 2011, 05:06 PM   #31
nige838 is offline nige838  United States
diyAudio Member
 
Join Date: Dec 2009
Quote:
Originally Posted by madtecchy View Post
Hi .
Are you still using the preamp section of the realistic amplifier ??
Ian
Hello,
Yes, I am still using the preamp, EQ, and FM radio as well as the original connections. Essentially all I have done is replace the power amplifier circuit with the LM3875s.
I'm a big fan of the tone controls on these old Realistic amplifiers. That and they look clean, nice wood finish. Not to mention that they were hand made in America.

Anyways, I've been too busy to work on it much. The more I listen to it, the more problems I notice. I think that I'm going to take the amps out, desolder the components, and use a PCB. Also, I want to use a better schematic...

Thanks for all of the advice. I have a much better understanding of what I'm doing now...
  Reply With Quote
Old 6th October 2011, 09:26 PM   #32
diyAudio Member
 
Join Date: Sep 2004
Location: Minneapolis, Minnesota, USA
Th3 uN1qU3, I don't know what kind of speakers Nige838 is using and niether do you, and while the point you make about limiting low frequency response for small speakers may be valid, it's a bad idea to limit frequency response in the feedback network to achieve that end, it should be done at the input of the amp.

Mike
  Reply With Quote
Old 7th October 2011, 12:24 AM   #33
diyAudio Member
 
Join Date: Feb 2010
Location: Bucharest
Send a message via Yahoo to Th3 uN1Qu3
Of course, but that's what's spec'd in the datasheet, and if he gets the circuit as presented to work fine, then he can modify it to his taste afterwards. It's always good to have a solid foundation to start upon.
__________________
"Audio grade" components simply means that they failed at a more critical job.
  Reply With Quote
Old 7th October 2011, 01:26 AM   #34
diyAudio Member
 
Join Date: Sep 2004
Location: Minneapolis, Minnesota, USA
It's been said many times on this forum that National's data sheets are not well witten in many instances, and thier chip amp data sheets are no exception. They are quite flawed with respect to the designed high pass roll-offs for input and feedback networks. The inputs have Fc set at .13 Hz, and the feedback Fc is set at 15.9 Hz, so if a sub-15 Hz signal finds its way to the input, the feedback network won't work as expected, resulting in instability and distortion. The main point I'm trying to make here is that it makes more sense to do it correctly in the beginning rather than do it wrong and then go back and fix it after the fact. Besides, what's the problem with putting in a 100uF cap instead of the 22uF on the data sheet? It won't cost much more and size won't be too much larger.

Mike
  Reply With Quote
Old 7th October 2011, 06:47 AM   #35
diyAudio Member
 
Join Date: Dec 2010
Location: wigan
Quote:
Originally Posted by nige838 View Post
Hello all,
I just completed my first gainclone. I gutted the main amplifiers on a old realistic stereo and implemented 2 LM3875s. I have a problem where when I turn the stereo off, it makes a POP and the speaker cone moves A LOT.
I'm running it a 55 volts, using this schematic
but instead of 5600uf caps on the + and -, I'm using 10000uf caps...

Why is the amplifier doing this? What can I do to fix the problem?

Thanks
Nige838 I would bet my bottom dollar the loud pop that you hear
is caused by the preamp section. Before you dismantle it disconect the input signals to the power amp and short its inputs to ground.
Then switch the amplifer on and then off there is a very good chance that
there will be a big reduction to the level of the pop you hear.
Would any of the thread hijackers like to comment and help provide suggestions to a solution.

Regards Ian
  Reply With Quote
Old 7th October 2011, 08:32 AM   #36
nige838 is offline nige838  United States
diyAudio Member
 
Join Date: Dec 2009
Quote:
Originally Posted by madtecchy View Post
Nige838 I would bet my bottom dollar the loud pop that you hear
is caused by the preamp section. Before you dismantle it disconect the input signals to the power amp and short its inputs to ground.
Then switch the amplifer on and then off there is a very good chance that
there will be a big reduction to the level of the pop you hear.
Would any of the thread hijackers like to comment and help provide suggestions to a solution.

Regards Ian
Many thanks Mad Tecchy. This makes sense to me. I will try this tomorrow. For tonight, this amp is pushing the jams for my birthday.

Much Appreciated.

I'm researching it..
  Reply With Quote
Old 8th October 2011, 12:44 AM   #37
diyAudio Member
 
Join Date: Sep 2004
Location: Minneapolis, Minnesota, USA
Nige838, after you've gotten your amp re-built correctly and have figured out that Madtecchy is right about the source of the popping problem, you might want to use this or something like it. The circuit is a speaker controller that will delay connecting the speakers to the amp output at power-on, immediatly disconnect speakers at power-off, and protect them from amplifier faults.

SPKR PROTECT.JPG
Speaker Protect BOM.txt

Mike
  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
Subwoofers too loud when barely turned up mfaughn Subwoofers 10 11th March 2011 02:08 AM
Gainclone makes my speakers go POP when lights turned off chylld Solid State 30 3rd July 2008 06:56 PM
'POP' sound when unit is turned off coki Car Audio 5 10th September 2007 08:56 AM
My amp only works after a while, or when turned up loud. boas Solid State 12 15th February 2007 11:16 PM
Pop when amp is turned off boostin1989 Solid State 6 10th October 2006 05:10 PM


New To Site? Need Help?

All times are GMT. The time now is 09:52 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