Bridging LM1875 into 4Ohms design with Forced fan Cooling ... Possible?? - 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 3rd June 2013, 02:24 PM   #1
diyAudio Member
 
dannyjmf's Avatar
 
Join Date: Feb 2010
Location: Malaysia - Melaka
Default Bridging LM1875 into 4Ohms design with Forced fan Cooling ... Possible??

Need help here ... i am helping a friend of mine to design an LM1875 Bridged amp X4 ... which means will use total of 8 LM1875's ... my friend wanted to use this amp for 4ohms speaker (bridged configuration) ... and the design will use force fan cooling total of 8 cooling Fans ... (4 blowing and 4 exhaust) ... will this able to handle 4 ohm in bridge mode?

thanks
  Reply With Quote
Old 3rd June 2013, 02:42 PM   #2
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 103
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Getting four paralleled amps stable isn't an easy job - why this approach? Why not a single LM3886 (for example)? What's the power requirement and are the fans being used instead of heatsinks?
__________________
No matter if we meanwhile surrender every value for which we stand, we must strive to cajole the majority into imagining itself on our side - Everett Dean Martin
  Reply With Quote
Old 3rd June 2013, 02:51 PM   #3
diyAudio Member
 
dannyjmf's Avatar
 
Join Date: Feb 2010
Location: Malaysia - Melaka
Btw is not a paralled but a bridged LM1875 ... i cant Find LM3886 in my place ... so this is the alternative ... my friend say he dont mind having a very large heatsink for this amp as we used cooling fan to cool the heatsink as much as possible

Anyway i have a 4channel LM1875 DIY ... tried to bridged them into 8ohms with no problems at all ... i wonder if it is 4ohms the IC will run into thermal protection if it overheats ... as if i am not mistaken these IC's have thermal cut off ...

Last edited by dannyjmf; 3rd June 2013 at 02:54 PM. Reason: extra notes
  Reply With Quote
Old 3rd June 2013, 03:03 PM   #4
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 103
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Ah, I see - apologies for my misunderstanding. So there are 4 channels - well the 1875s will 'see' a 2R load when bridged which they won't take too kindly to. Whether it thermally overheats will depend mainly on the supply voltages, then on the music you play and probably after that, on the heatsinking. Certainly you'll get worse distortion with 2R load but whether it will be audible is debatable.
__________________
No matter if we meanwhile surrender every value for which we stand, we must strive to cajole the majority into imagining itself on our side - Everett Dean Martin
  Reply With Quote
Old 3rd June 2013, 03:28 PM   #5
diyAudio Member
 
dannyjmf's Avatar
 
Join Date: Feb 2010
Location: Malaysia - Melaka
well ... since this project is confirmed to be build soon ... i will let u know later ....
  Reply With Quote
Old 3rd June 2013, 06:45 PM   #6
Bone is offline Bone  United Kingdom
diyAudio Member
 
Join Date: Jun 2004
Location: Dorset, UK
A parallel bridge may work. This would work into 4 ohms. Also uses 4 1875s could give you about 100w
  Reply With Quote
Old 5th June 2013, 12:00 PM   #7
JMFahey is offline JMFahey  Argentina
diyAudio Member
 
JMFahey's Avatar
 
Join Date: Mar 2009
Location: Buenos Aires - Argentina
Once you get into that level of complexity, chipamps lose attractive, I'd go discrete .
Plus they limit you a lot, specially on PSU voltage.
Once you start *needing* to bridge + parallel them to meet a power output goal, in my book it means you are going way beyond what was originally expected from them.
Just saying.
  Reply With Quote
Old 6th June 2013, 05:13 PM   #8
blu_glo is offline blu_glo  England
diyAudio Member
 
blu_glo's Avatar
 
Join Date: Aug 2005
Location: London, England
I second that, JMFahey, is less complicated to go discrete. Theres only one chip that really lends itself to 4 ohm bridging - the aforementioned LM3886 - would still limit around 120W.....
  Reply With Quote
Old 7th June 2013, 02:06 AM   #9
diyAudio Member
 
Join Date: Jun 2004
Location: uruapan, michoacan, mexico
Excuse my intromision, but what about the parallel TDA 7293 ?
I{m just about finishing one to use it with a 4 ohm load.
Would it be a better solution, or not?
  Reply With Quote
Old 7th June 2013, 02:59 AM   #10
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 103
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Yes, TDA7293 is the easiest solution for a bridged chipamp into 4ohms. With 4 chips you'll be looking at a maximum power over 200W.
__________________
No matter if we meanwhile surrender every value for which we stand, we must strive to cajole the majority into imagining itself on our side - Everett Dean Martin
  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
Forced cooling of toroid transformer rikkitikkitavi Power Supplies 2 12th November 2012 10:28 PM
Forced cooling tunnel and some transistors ric-paul Swap Meet 0 10th April 2012 08:17 AM
fan cooling? Raj1 Pass Labs 22 8th January 2003 02:33 PM
FS: Forced cooling tunnel webercarbmann Swap Meet 0 27th November 2002 08:50 PM


New To Site? Need Help?

All times are GMT. The time now is 12:09 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