How to make LME49810 amp 2 ohm stable? - diyAudio
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Old 13th November 2012, 10:05 AM   #1
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Default How to make LME49810 amp 2 ohm stable?

im thinking to buy this module as matching transistors will be much more expensive for a 5 pair output stage.
http://www.connexelectronic.com/docu...ier_Module.pdf

now the problem is that we would be driving two 15 inch drivers in parallel with effective imp 4 ohms... now I just want to know two things..

1. what to do so that the amp is stable in 2 ohms for driving those 15 inch drivers..

2. How much current can be delivered by each transistor in operation.

4.If high VA psu is placed then does the amp be stable in 2 ohms?
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Old 13th November 2012, 10:14 AM   #2
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For a proper 2 ohm operation the output stage must be a Triple emitter follower one a.k.a 3-deep darlington, though the LME49180 shows an inbuilt pre driver stage but the effectiveness cannot be tested until experimented. Also the output transistors are less in numbers for what is required in 2 ohm operation.Other things like heatsinks and powersupply also needs to be doubled up.

If you want to drive the amp on +/-84 rails then at 2 ohms the power would be around 1kw provided the supply is rock solid and not sagging, which means the total output current would be 63A peak, going for atleast 10 pairs in output puts each device around 6A of load current sharing.

Basically this design is not a pro-audio one, better get something more robust .

Last edited by Workhorse; 13th November 2012 at 10:18 AM.
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Old 13th November 2012, 12:07 PM   #3
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what has to be done to make this module for pro audio application. Considered it can be used at 4ohm.

For 500W
Im using 1KVA R-Core psu with CRGO core material.
1,00,000uf / 100v one big capacitor for each rail.

For 1000W i would be using 2KVA psu

I would like how can I add more output transistors? how many pairs can be added for that driver?

I would like to drive this one..
http://www.jblpro.com/catalog/genera...?PId=117&MId=3

the speaker is rated as 1200RMS into 4 ohms.

Thought to use two of that above modules in bridged mode with DRV134..

Last edited by rhythmsandy; 13th November 2012 at 12:20 PM.
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Old 13th November 2012, 05:03 PM   #4
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Parallel more devices just like they are with 5 pairs already.
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Old 14th November 2012, 12:48 PM   #5
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the driver stage contains 2SA1930 2SK5171 can it support 10 pairs of output devices? will the amp be stable at 10 pairs of output devices?
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Old 14th November 2012, 03:28 PM   #6
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I would simply use lower rails.
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Old 14th November 2012, 06:27 PM   #7
sangram is offline sangram  India
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Lower rails and higher bias will be needed.

I'm curious though, why not connect the drivers in series? That pretty much solves the issue as ultimately you will be limited by total dissipation of the module.
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Old 14th November 2012, 07:50 PM   #8
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High voltage class AB amps are unpractical as they dissipate a lot and weigh a ton.
Better to go classD or H imho.
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Old 14th November 2012, 08:28 PM   #9
tinitus is offline tinitus  Europe
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making amp 2ohm stable is no big problem, if not actually driving 2ohm speakers
heatsinks should be like classA

but maybe think balanced
two modules bridged, each running at maybe 40V rails
but thats just guessing

but are they reliable enough
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Old 14th November 2012, 08:36 PM   #10
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by rhythmsandy View Post

For 500W
Im using 1KVA R-Core psu with CRGO core material.
1,00,000uf / 100v one big capacitor for each rail.

For 1000W i would be using 2KVA psu

you have no idea what you are doing
better forget about it
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