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j.wright 4th June 2008 09:57 PM

LM4780 in parallel...?
I'm new to building amplifiers so please forgive my ignorance...

Is it possible to use multiple IC amplifiers in an effort to generate more power ?

For example:
The LM4780 amp is rated at 60 watts x2 and 120watts x 1. If I wanted to build a 360 watt x 1 amplifier could I parallel 3 LM4780 amp together to add up to the 360 watts ?


ionomolo 4th June 2008 11:10 PM

I belive that 360W needs too much voltage 200W is possible, i will suggest you to read AN-1192 about bridging/paralleling LM3886's (an LM4780 are two of these in the same package).

If you need > 350W there are chipamps that will do, but sure that you need that power?

AndrewT 5th June 2008 12:38 PM

output power is all about voltage and current.

If one chipamp can push 60W into 8ohms, then that comes about from the voltage and current that is available from that chipamp.
Those maxima cannot vary.

Now parallel two chipamps and try to drive a load with half the impedance i.e. 4ohms.
You can, with care, get 120W into 4ohms. The voltage is the same as before and the current from EACH chipamp is the same as before.

Now parallel 4chipamps into 2ohms. You get 240W into 2ohms.
Check out the voltage and current again. What do you find?

Why do you want so much power?
Is there a better way to achieve that SPL?
Have you considered more efficient speakers or a circuit better suited to higher voltage supply rails?

djk 5th June 2008 01:28 PM

Here is your 400W chip amp.,M1

Each '3386' will need to be four sections in parallel for 400W out.

Use the biggest Hexfet you can find.

j.wright 5th June 2008 08:08 PM

I would like to have 300-500 watts for a subwoofer channel...

How would you guys suggest doing that ?


AndrewT 6th June 2008 08:59 AM

have a look at the quasi threads.

j.wright 6th June 2008 02:49 PM

Quasi threads ?

AndrewT 6th June 2008 04:46 PM

search quasi

SpittinLLama 9th June 2008 06:30 PM

Look at the LME49810, LME49811, LME49830 or LM4702 from National. You will need to put your own output stage and then some protection if you want it but you can make an amplifier in this power range pretty easily. Or search for a fully discrete design that does what you need. Using chip amps will work but will be some effort.


SpittinLLama 9th June 2008 10:24 PM

Just for more info, you will need a 4 ohm speaker (driver). Then you will need either 6 or 8 amplifier channels. Half of the amplifier channels will be on one side of the bridge and the other on the other side. This could be all LM3886 chips or half that using LM4780 chips. The supply voltage will need to be around 30V, depends on how you do the full design. If you want to be more conservative, then go for 8 amp channels and target about 50W of output power per amp. This means a 4 ohm load will look like 8 ohms for each amp channel. So you will have 4 amplifier channels in parallel on each side of the bridge. Power supply voltage will be +/-32V - +/-35V. This will get you the 400W you want into a load.


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