LME49810 with 2sa1943 and 2sc5200

xeclipse · 13th July 2010, 08:26 PM

Hi guys,
I am looking forward to build an amp using these devices from scratch.I've done a lot of research thats why i settled for those.
I need a mono amp,200w into 8 ohm load.
I have several questions:
-with a supply of +/-50 volts,how many pairs of output devices will i need?
-which output topology to use (efficient and simple).I envy QSC rmx 850 output topology.
-with such power,will drivers be really needed?
I already have the power supply with 10,000 uF per rail and more than enough heat sink.
A working schematic with the pcb layout will greatly help. I am looking for simplicity since its my first solid state amp,those are the reasons that made me go for the lme chip.
I'll also appreciate tips on preventing thermal runaway.

Regards Xeclipse.

nigelwright7557 · 13th July 2010, 09:12 PM

>-with a supply of +/-50 volts,how many pairs of output devices will i need?
2 pairs should cope OK.

>-which output topology to use (efficient and simple).I envy QSC rmx 850 >output topology.
You will need drivers after the VAS.
>-with such power,will drivers be really needed?
Yes.

>I'll also appreciate tips on preventing thermal runaway.
Use a Vbe multiplier with the transistor on the heatsink or glued on an output transistor is even better.

xeclipse · 14th July 2010, 05:19 AM

Thanks for the info Nigelwright7557.Some of that are in the chip's datasheet.
I still got a few questions,will parallel outputs go well with the chip?I noticed that in the datasheet the outputs are in emiter follower topology.
What do i look for in a Vbe multiplyer transistor?Is there any you recommend?
Regards.

sakis · 14th July 2010, 07:00 AM

here is a schematic

andrewlebon · 14th July 2010, 07:27 AM

hi xeclipse
greetings want to make simplest class ab amp r u interested
e mail me
thanking you
andrew lebon

sakis · 14th July 2010, 07:36 AM

yes of course ... even the John fisher amplifier is somewere arround here .....

AndrewT · 09:43 AM

+-50Vdc for a supply cannot give 200W into 8r0.
It can give 100W into 8r0 and/or 200W into 4r0.
If you need 200W into 8r0 then increase the supply to +-65Vdc.

Your 1943/5200 better suit the lower voltage (+-50Vdc) than the higher voltage.

1pair for 100W into 8ohm (35+35Vac)
2pair for 200W into 4ohm (35+35Vac)
3pair for 200W into 8ohm (45+45Vac)
provided you keep them cool.

homemodder · 14th July 2010, 10:37 AM

Sakis whos the designer of that amp, 22ohms for base stoppers to the output transistors ???? I think no good.

xeclipse · 14th July 2010, 10:56 AM

Thanks for the schematic Sakis,i really appreciate it.

xeclipse · 14th July 2010, 11:04 AM

Hi Homemodder,i also noticed that.I don't think the resistors are even necessary.
Hi Andrew T,what's the expected power output using 2 pairs with the same supply into 4 ohms?I got sufficient cooling.
Regards

13th July 2010, 08:26 PM	#1
xeclipse diyAudio Member Join Date: May 2010 Location: Where the world's best tea come from:Kericho Kenya	LME49810 with 2sa1943 and 2sc5200 Hi guys, I am looking forward to build an amp using these devices from scratch.I've done a lot of research thats why i settled for those. I need a mono amp,200w into 8 ohm load. I have several questions: -with a supply of +/-50 volts,how many pairs of output devices will i need? -which output topology to use (efficient and simple).I envy QSC rmx 850 output topology. -with such power,will drivers be really needed? I already have the power supply with 10,000 uF per rail and more than enough heat sink. A working schematic with the pcb layout will greatly help. I am looking for simplicity since its my first solid state amp,those are the reasons that made me go for the lme chip. I'll also appreciate tips on preventing thermal runaway. Regards Xeclipse. __________________ if there are no sparks,it probably doesn't work!

13th July 2010, 09:12 PM	#2
nigelwright7557 diyAudio Member Join Date: Apr 2008 Location: Carlisle, England	>-with a supply of +/-50 volts,how many pairs of output devices will i need? 2 pairs should cope OK. >-which output topology to use (efficient and simple).I envy QSC rmx 850 >output topology. You will need drivers after the VAS. >-with such power,will drivers be really needed? Yes. >I'll also appreciate tips on preventing thermal runaway. Use a Vbe multiplier with the transistor on the heatsink or glued on an output transistor is even better. __________________ http://www.murtonpikesystems.co.uk PCBCAD40 pcb design software.

14th July 2010, 05:19 AM	#3
xeclipse diyAudio Member Join Date: May 2010 Location: Where the world's best tea come from:Kericho Kenya	Thanks for the info Nigelwright7557.Some of that are in the chip's datasheet. I still got a few questions,will parallel outputs go well with the chip?I noticed that in the datasheet the outputs are in emiter follower topology. What do i look for in a Vbe multiplyer transistor?Is there any you recommend? Regards. __________________ if there are no sparks,it probably doesn't work!

14th July 2010, 07:36 AM	#6
sakis diyAudio Member Join Date: Jan 2006 Location: nea makri athens greece	yes of course ... even the John fisher amplifier is somewere arround here ..... __________________ SERVICE ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr

14th July 2010, 09:35 AM	#7
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	+-50Vdc for a supply cannot give 200W into 8r0. It can give 100W into 8r0 and/or 200W into 4r0. If you need 200W into 8r0 then increase the supply to +-65Vdc. Your 1943/5200 better suit the lower voltage (+-50Vdc) than the higher voltage. 1pair for 100W into 8ohm (35+35Vac) 2pair for 200W into 4ohm (35+35Vac) 3pair for 200W into 8ohm (45+45Vac) provided you keep them cool. __________________ regards Andrew T. Last edited by AndrewT; 14th July 2010 at 09:43 AM.


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14th July 2010, 07:27 AM	#5
andrewlebon diyAudio Member Join Date: Feb 2008	hi xeclipse greetings want to make simplest class ab amp r u interested e mail me thanking you andrew lebon

14th July 2010, 10:37 AM	#8
homemodder diyAudio Member Join Date: May 2006	Sakis whos the designer of that amp, 22ohms for base stoppers to the output transistors ???? I think no good.

14th July 2010, 10:56 AM	#9
xeclipse diyAudio Member Join Date: May 2010 Location: Where the world's best tea come from:Kericho Kenya	Thanks for the schematic Sakis,i really appreciate it. __________________ if there are no sparks,it probably doesn't work!

14th July 2010, 11:04 AM	#10
xeclipse diyAudio Member Join Date: May 2010 Location: Where the world's best tea come from:Kericho Kenya	Hi Homemodder,i also noticed that.I don't think the resistors are even necessary. Hi Andrew T,what's the expected power output using 2 pairs with the same supply into 4 ohms?I got sufficient cooling. Regards __________________ if there are no sparks,it probably doesn't work!

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