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east electronics 21st July 2007 07:32 PM

powerfull schematic
 
2 Attachment(s)
this is something i found on national book based on lm12clk

considering that is powered on rails of 100volts should produce a hell of lot of power ...

any body ever build a thing like that ????

opinions are very welcome

thank you ......sakis

east_electronics@yahoo.gr

Conrad Hoffman 21st July 2007 07:37 PM

Never tried stacking them, but did build some LM12 amps. IMO, the input specs are pretty bad, so I buffered it with an opamp and (I think) wrapped the feedback around the pair. Worked well, but I think the newer power parts are better performers.

gaetan8888 22nd July 2007 12:36 AM

Hello

If you want a chip amp, try TDA7293 or LM3886 , they are much better sounding than the LM12.

Gaetan

east electronics 22nd July 2007 07:32 AM

thanks conrad gaetan
 
well yes true i ve was playing in the past but only once with lm 12 but the particular part was very terrible i think made may be in bulgaria very cheap so i can really tell

gaetan .... to my understanding this schematic will easily produce 200 w @ 8R the question is there a schematic with lm3886 and or other that can easily produce this kind of power ????

can lm 3886 be "boosted " with outside transistors ?????

there is a topology if remember well from original sgs books and tda 2030 boosted with a pair of BD911-12 ....this i tryied produces some 40-45w on the bench but its extremelly stable and very dynamic also .....

could this have simular behavior ????

ilimzn 22nd July 2007 11:52 AM

Note that the LM12 is operated permanently out of 36V lines local to it and that the rest of the voltage drop is on the xternal darlingtons. Also note what the load resistor is! Even though the principle is sound, operating a low mpedance load with the attached schematic is not likely, think of the SOA required from the external parts.

ashok 22nd July 2007 12:12 PM

Tried a boosted LM3886 in 2006.
 
I tried the LM3886 with external transistors , similar to the TDA2030 scheme. This seems to be quite an old circuit as I remember seeing it long ago ( late 70 's ? ) in Wireless World. That application was with opamps.

Anyway , the FFT distortion plot of the amp was much inferior compared to the stand alone LM3886 within its own ratings ( without external transistors) . So I dropped the idea of trying to use it. The odd order went up quite a lot. Maybe it can be tweaked further to improve the performance.
However it certainly works. I played it too and I can't remember too well how good it sounded . But I can say that it certainly didn't sound bad . My reason for dumping it was the poor FFT that I got !

I did think up of some other component changes but never got round to trying it. I plan to do it some time soon as the original boards and heat sinks are still around.
Note that I built only one channel and ran it at +/- 35 volts into two 8 ohms speakers in parallel ( effectively 4 ohms with dips to 2.9 ohms) . It drove them happily without any strain until the normal clipping point. Even slightly clipped it was good. Meaning that mild clipping didn't cause the sound to go to pieces. The heat sinks got very hot. Interesting enough to follow up and tweak.
Cheers.

east electronics 22nd July 2007 02:49 PM

true.....
 
i was thinking the same ilimzn and yet the lm 12 stand alone requiers a lot on cooling and stability considering thermals but also pcb design versus ocilation locally created and good routing between in and out ......

stil i am willing to try and especially now that it seems nobody else did....from the previous aplication i ve been runnig i.e tda 2030 boosted with bd 912+11 i know for shure that this amp loves inductive loads and it was very stable even driving speakers or transformers in 100v application

i will produce something i call surface mount pcb that gives me thermal stability .... in a few days .... will see

the good think is that i can have many of lm 12 clk .....and in good prize also he he he so will see how its going

AndrewT 22nd July 2007 03:21 PM

Hi,
does the 750r on the output indicate the recommended value of load?

If so then we are talking about 5W output. (90^2/750/2)

Symon 22nd July 2007 06:20 PM

Hi Andrew,
No the 750 ohm is only part of the drive for the output stage.
The actual speaker load is from the end of L1, near the input
terminal. So it can drive much heavier loads.

- Symon

gaetan8888 22nd July 2007 06:53 PM

Re: thanks conrad gaetan
 
2 Attachment(s)
Quote:

Originally posted by sakis
well yes true i ve was playing in the past but only once with lm 12 but the particular part was very terrible i think made may be in bulgaria very cheap so i can really tell

gaetan .... to my understanding this schematic will easily produce 200 w @ 8R the question is there a schematic with lm3886 and or other that can easily produce this kind of power ????

can lm 3886 be "boosted " with outside transistors ?????

there is a topology if remember well from original sgs books and tda 2030 boosted with a pair of BD911-12 ....this i tryied produces some 40-45w on the bench but its extremelly stable and very dynamic also .....

could this have simular behavior ????

Hello

Yes, find the an1192.pdf file, use google to find it.

There is a parallell-bridge 200watt version of the lm3886 in that file.

Here a small image of that schematic.

Gaetan


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