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Old 30th May 2005, 06:15 PM   #1
kinser is offline kinser  Israel
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Default Help with GC power supply

Hi all,
Long time no post....

I am planning on building a GC with OPA541 or OPA549, and i think im going to go with the 549 from what people here have said.. its got more power and sounds better... BUT it max V+/- is 30Vdc.. and i have a 25-0-25 260va EI trafo.. how should I lower the voltage from 35vdc+/- to about 25-28vdc+/-? would 1 pair of LM317/337 do the job?

Thanks,
Kinser
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Old 30th May 2005, 06:19 PM   #2
lgreen is offline lgreen  United States
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That should work. Make sure you get good heat sinking on those regulators.
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Old 30th May 2005, 06:23 PM   #3
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317/337 should get pretty hot

Why don't you look in the "LM338 regulated snubberized PSU for audio amplifiers" thread

LM338 is the 5A version of the 1A LM317

http://www.diyaudio.com/forums/attac...amp=1114473823
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Old 30th May 2005, 06:23 PM   #4
kinser is offline kinser  Israel
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lgreen,

Thanks for the help... forgot to mention.. its a stereo amp.. so a pair of the LM317/337 will do with heatsinks, with 2 549's?

Thanks,
Kinser
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Old 30th May 2005, 06:27 PM   #5
kinser is offline kinser  Israel
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tobias_svensk,

Thanks for that.. had a look at it befor.. would rather not use it... becuase i want to keep this amp as small and simple as possible..can i use LM338 with both positive and negative rails? or does it have another chip to go with it?(eg, LM338 for positive rail, LMxxx for negative rail)

Thaks,
Kinser
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Old 30th May 2005, 07:14 PM   #6
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Two LM338 will work if you connect them as in the picture.

You could always put some smaller caps in the LM338 supply to keep down the size. Because the LM338 & LM317 is the same size anyways.

And driving a stereo amp with one LM317 plus one LM337? i can't see that coming.

You could try an unregulated psu, just do a simple CRC or CRCR or whatever is popular
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Old 30th May 2005, 07:44 PM   #7
kinser is offline kinser  Israel
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So,
What I should do is make 2 LM338 circuits.. connect 1 normal.. to the positive rail.. and then with the 2nd ciruit i connect the "In" to the center tap/ground, and the com/ground to the negative rail? like in the ciruit using the 338's? but the circuit will be with smaller/less components...
Does this all make sense to you? and is it the way to do it?

Thanks,
Kinser
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Old 30th May 2005, 07:55 PM   #8
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Hi Kinser, don't make it crazy, use OPA 541, which have higher voltage ( +/- 40 V ), but it is old circuit, with nonextraordinary parametres , better is to use some LM... circuit.
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Old 30th May 2005, 08:02 PM   #9
kinser is offline kinser  Israel
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Upupa Epops,

Thank you! I will go with 541's.. much more simple.. although i really want to us 549's.. if i had some LM's i would use em'.. but i have none left.. they were sample from national.. and they are not cheap here.. at least not cheap for me...the are cheap for big companys and repair-men...
BTW.. Im only 14 years old... heheh

Thanks Alot!! :-)
Kinser.. will show you resalts in a couple of days!
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Old 30th May 2005, 08:11 PM   #10
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Don't drink so much Cola's and money will be no problem . Good luck.
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