Help with GC power supply

kinser · 30th May 2005, 06:15 PM

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

lgreen · 30th May 2005, 06:19 PM

That should work. Make sure you get good heat sinking on those regulators.

tobias_svensk · 30th May 2005, 06:23 PM

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

kinser · 30th May 2005, 06:23 PM

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

kinser · 30th May 2005, 06:27 PM

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

tobias_svensk · 30th May 2005, 07:14 PM

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

kinser · 30th May 2005, 07:44 PM

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

Upupa Epops · 30th May 2005, 07:55 PM

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.

kinser · 30th May 2005, 08:02 PM

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!

Upupa Epops · 30th May 2005, 08:11 PM

Don't drink so much Cola's and money will be no problem

. Good luck.

30th May 2005, 06:15 PM	#1
kinser diyAudio Member Join Date: Jan 2004 Location: R'aanana	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

30th May 2005, 06:19 PM	#2
lgreen diyAudio Member Join Date: May 2003 Location: San Diego, USA	ps That should work. Make sure you get good heat sinking on those regulators.

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30th May 2005, 06:23 PM	#3
tobias_svensk diyAudio Member Join Date: Jan 2004 Location: Hudiksvall	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

30th May 2005, 06:27 PM	#5
kinser diyAudio Member Join Date: Jan 2004 Location: R'aanana	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

30th May 2005, 07:14 PM	#6
tobias_svensk diyAudio Member Join Date: Jan 2004 Location: Hudiksvall	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

30th May 2005, 07:44 PM	#7
kinser diyAudio Member Join Date: Jan 2004 Location: R'aanana	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

30th May 2005, 07:55 PM	#8
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	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.

30th May 2005, 08:02 PM	#9
kinser diyAudio Member Join Date: Jan 2004 Location: R'aanana	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!

30th May 2005, 08:11 PM	#10
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	Don't drink so much Cola's and money will be no problem . Good luck.