bridge parallel with 4 LM4780s? Done before?

lgreen · 03:21 AM

Has anyone bridge paralled 4 LM4780s? This would be 4 amps in parallel (3886) bridged with 4 other amps (3886) in parallel. Of course I would use reallly high % resistors to set gain and output trying to ensure that all parallel amps behave exactly the same.

It turns out I have the boards, I have the chips, I have the heatsink, I have the DRV134s, I have the soft start, I have the diodes, I have the caps, I have the XLRs and RCAs, I have the speaker binding posts, and I have the case. A few resistors and a transformer and its done. Seems too simple.

Looking at the SOA I would probably not want to drive with +/- 35VDC but I would like the operational voltage to be about +/- 30VDC if that is feasible. I do not know what kind of sag to expect but if I am doing this i'd like to get as most power out as I can given that the heat sinks will be huge.

sangram · 21st November 2009, 05:55 AM

I've done half of what you're planning, with 4 LM4780s total in a stereo setup - 4 amplifiers per channel. Lots of drive, 30V supplies ensured clean and reliable operation even into 4 ohm loads with reasonable heatsinking. I still have them lying around, but my tastes have veered towards higher fidelity, if lower power so I'm now on P2P chipamps with some quality components.

With twice the number of amps, I would guess 35V rails would be safe. IIRC Jeff Rowland had 6 amps/channel and a transformer to balance the inputs....

Francec · 21st November 2009, 11:42 PM

It is something I'm thinking of doing in the next 6 months, so that I can drive the 10" high Xmax woofers that aren't bought yet for my active 3-way. I will be using +-35V that I am currently using for bridged LM3886TF amps. Look for to progress on this.

Frank

tt · 22nd November 2009, 01:55 PM

This diyer made his amps with 4 LM4780s only.

http://bbs.audiohall.net/viewtopic.p...r=asc&start=33
http://bbs.audiohall.net/viewtopic.p...r=asc&start=79
http://bbs.audiohall.net/viewtopic.p...=asc&start=113

21st November 2009, 03:16 AM	#1
lgreen diyAudio Member Join Date: May 2003 Location: San Diego, USA	bridge parallel with 4 LM4780s? Done before? Has anyone bridge paralled 4 LM4780s? This would be 4 amps in parallel (3886) bridged with 4 other amps (3886) in parallel. Of course I would use reallly high % resistors to set gain and output trying to ensure that all parallel amps behave exactly the same. It turns out I have the boards, I have the chips, I have the heatsink, I have the DRV134s, I have the soft start, I have the diodes, I have the caps, I have the XLRs and RCAs, I have the speaker binding posts, and I have the case. A few resistors and a transformer and its done. Seems too simple. Looking at the SOA I would probably not want to drive with +/- 35VDC but I would like the operational voltage to be about +/- 30VDC if that is feasible. I do not know what kind of sag to expect but if I am doing this i'd like to get as most power out as I can given that the heat sinks will be huge. __________________ My DIY audio projects- PartTimeProjects.com. Last edited by lgreen; 21st November 2009 at 03:21 AM.

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21st November 2009, 05:55 AM	#2
sangram diyAudio Member Join Date: Sep 2002 Location: Calcutta, India	I've done half of what you're planning, with 4 LM4780s total in a stereo setup - 4 amplifiers per channel. Lots of drive, 30V supplies ensured clean and reliable operation even into 4 ohm loads with reasonable heatsinking. I still have them lying around, but my tastes have veered towards higher fidelity, if lower power so I'm now on P2P chipamps with some quality components. With twice the number of amps, I would guess 35V rails would be safe. IIRC Jeff Rowland had 6 amps/channel and a transformer to balance the inputs....

21st November 2009, 11:42 PM	#3
Francec diyAudio Member Join Date: Jul 2006 Location: Port Melbourne	It is something I'm thinking of doing in the next 6 months, so that I can drive the 10" high Xmax woofers that aren't bought yet for my active 3-way. I will be using +-35V that I am currently using for bridged LM3886TF amps. Look for to progress on this. Frank

22nd November 2009, 01:55 PM	#4
tt diyAudio Member Join Date: Aug 2004 Location: New York, NY	This diyer made his amps with 4 LM4780s only. http://bbs.audiohall.net/viewtopic.p...r=asc&start=33 http://bbs.audiohall.net/viewtopic.p...r=asc&start=79 http://bbs.audiohall.net/viewtopic.p...=asc&start=113

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