Bridge/Parallel Configuration Help - 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 8th March 2005, 05:59 PM   #1
mothman is offline mothman  United States
diyAudio Member
 
Join Date: Apr 2003
Location: Gaithersburg,Maryland
Default Bridge/Parallel Configuration Help

Hello,

Can the more experienced among you explain how two chips are wired in parallel or bridged?....Iv'e built a LM3886 clone thats been up and running and sounding good for almost two years.
I havn't visited the forum in quite some time and was interested in the new LM4780?(the one thats two 3886 on the same die)and how you actually,physically connect the pins for bridge and or parallel mode.
I have looked at the NSC App. notes and schematics but it's a little beyond my knowledge level.
Here's the questions I'm asking and they may sound stupid so bear with me:

1) If the LM4780,a two channel stereo chip, is composed of two LM3886 chips how do you physically combine them to make a more powerfull one channel amp.

2) I'm running 4ohm speakers and understand that parallel chips share the load for better performance yes?

Thanks for your help
__________________
R.C.D
  Reply With Quote
Old 8th March 2005, 06:10 PM   #2
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
the heatsink required to run bridged into 4 ohms would be quite large -- since the chip dissipates 4X the amount of heat in this configuration. you could try it with 24V on each rail.

nat semi has the parallel configuration on the product PDF -- it's pretty straightforward.
  Reply With Quote
Old 8th March 2005, 08:01 PM   #3
Banned
 
Join Date: Aug 2002
Location: New York, NY
Send a message via AIM to yldouright Send a message via Yahoo to yldouright
Yeah, the consensus is that these chips are 'mui caliente' and members who are using it say that the pinout is less than layout friendly. On a related topic, has anyone here tried to "T" the LM4780?
  Reply With Quote
Old 8th March 2005, 08:22 PM   #4
K-amps is offline K-amps  United States
diyAudio Member
 
K-amps's Avatar
 
Join Date: Nov 2003
Location: Indiana
I am not sure if your mean simultaneous series/ parallel bridging or just plain... I will explain the former:

You will need 2 LM4780's to create one hi-powered channel.

In Chip 1, you use the non-inverting inputs fed by a common source. On the outputs you use 0.22ohm to connect the two outputs together to form one channel. (Like paralleling discrete output devices). You have just parallel bridged this chip. This chip 1 will become the top half of your overall Paralell/Series bridge channel.

In chip 2 you you do the same as chip 1 except you use the "inverting" inputs fed by the same common source feeding Chip1. You parallel bridge the 2 outputs via 0.22 ohm on this Chip as well. This chip forms the bottom half of your bridge.

Lastly you connect the 2 chip's outputs to a load to get output (i.e. Series bridge).

Chip 1's outputs goes to the "+" of your speaker and Chip 2's outputs goes to the "-" of your speakers.

As mentioned earlier, your dissipation is 3x to 4x depending how stiff your power supply is, so you need to dissipate all that heat.

See http://cache.national.com/ds/LM/LM4780.pdf it shows both paralell and series bridging, you will need to do both.

I do not work with Chip amps so I do not know how reliable the LM will be in this application, I just mentioned how it's done since you asked.
  Reply With Quote
Old 9th March 2005, 02:38 AM   #5
diyAudio Member
 
Join Date: Dec 2001
Location: SIUE, Illinois, USA
on the side note:
yes. about a year ago i built a bridged T clone network on a lm4780 for the purpose of a 120W @ 8ohm application. I called it the hi3gc (high input impedance inverting gain clone), and used a 100k + 1uF capacitor for the DC blocking filter. the results were good overall, but a 70mV offset existed (50mV on one amp, -20mV on the other, 70mV combined). otherwise everything was fine. Mine was run hot -- the thing was barely specced to run according to national. however since i ran it for at most 10 minutes at high power (this was a dorm room) i figured i was fine.
the phase inversion for bridging was done by a preamp inverting amplifer.

in a good parallel configuration, each amp will see twice the load impedance -- supplying half the current. however parallel can be bad because you could have 10V on one amp, and 10.1V on the other amp. the 0.1V difference seems trivial until you concider the 0.1ohm resistance between the two amps, in which case one amp will seem like a 1A current sink! the use of output resistors and other matching networks help to limit the cross-current to low values.
__________________
if only it could be used for good, not evil...
  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
Parallel Bridge? rgrayton Chip Amps 16 20th January 2009 03:50 PM
Levinson ML-3 mono parallel configuration RobertS61 Solid State 6 12th July 2007 07:26 AM
Bridge Parallel AMP myanmar Chip Amps 15 11th March 2007 09:02 AM
Is a bridge / parallel configuration of 3875 is better for my speaker ? 100db Chip Amps 7 8th March 2006 10:42 AM
parallel or bridge rulezzz Chip Amps 1 8th January 2004 06:59 PM


New To Site? Need Help?

All times are GMT. The time now is 06:06 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