How to make LME49810 amp 2 ohm stable?

[rhythmsandy]

im thinking to buy this module as matching transistors will be much more expensive for a 5 pair output stage.
http://www.connexelectronic.com/documents/LME49810_Audio_Amplifier_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?

 

[kASD]

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 .

 

[rhythmsandy]

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/general/product.aspx?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..

 

[kASD]

Parallel more devices just like they are with 5 pairs already.

 

[rhythmsandy]

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?

 

[bobodioulasso]

I would simply use lower rails.

 

[Sangram]

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.

 

[bobodioulasso]

High voltage class AB amps are unpractical as they dissipate a lot and weigh a ton.
Better to go classD or H imho.

 

[tinitus]

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

 

[tinitus]

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

 

[bobodioulasso]

Simply, no. Bridging is not good for low Z.

 

[tinitus]

no, I know its not
but with 2x 5pair outputs, running at 40Vdc ?
it ought to last forever

better than a 1000watt driving 2ohm (?)

btw, I have a 2ohm stable 40watt with just one output pair, and it can actually drive a 2ohm speaker, no problem

 

[rhythmsandy]

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

actually the above config is for 4 ohms not for 2 ohms...

using a 2kva suppy for class AB and expecting 1000watts wouldnt be a problem I believe... or we might even increase the psu to 3kva for more headroom...

 

[rhythmsandy]

i think this one would be sufficient for driving it in 4 ohms..
1000W Mono High Power Amplifier AMP For Home Audio Or Stage Use

13 pairs of output devices...

 

[rhythmsandy]

what should be the voltage supply if i want to bridge the 500W into 4 ohms amplifiers..

the load imp of the speaker will be about 4 ohms.

If its single module the amp can go upto 550w in 4 ohms with +/-80v supply..

now if its bridged then what should be the voltage supply?

 

[bobodioulasso]

500w into 4R is 63volts at speaker.
Count losses, psu sagging.
About 73 volts rails will do .
Forget about bridging which brings more voltage but no more current at the speaker.

Edit:
Looking at Connex. 550 w moule specs, 78v rails 4R load is plenty

 

[panson_hk]

High voltage class AB amps are unpractical as they dissipate a lot and weigh a ton.
Better to go classD or H imho.

I agree with you. I would use high-power Class D instead a monster Class AB as this is for a sub.

 

[tinitus]

i think this one would be sufficient for driving it in 4 ohms..

13 pairs of output devices...

I dont understand, why the connex
1000watt amp module fully assembled and tested ? yeah, right

using a 2kva suppy for class AB and expecting 1000watts wouldnt be a problem I believe... or we might even increase the psu to 3kva for more headroom...

ok, no problem
I have 2kVA trafos, and I can barely lift just one of them

 

[tinitus]

Looking at Connex. 550 w moule specs, 78v rails 4R load is plenty

ah, its standard specs ? the shown heatsink looks a bit small for that

but this 1200watt from Ground Sound I would trust more

quote
The maximum power output depends on voltage supply, heat sink and load conditions. Recommendations: Voltage supply of + / - 95V, heat sink less than 0,2 K / W and minimum load of 1,5Ω.

 

[bobodioulasso]

Just meant rails voltage. Of course heatsink has to be a lot larger and even need a fan.
Anyway, at that power, current limiters are a must. I do not see any in the connex module.