Help with GC power supply

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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 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)

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 :)
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?

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!
Hey again,

I have 2 q's...
1.this might be kind of off topic - does anyone have a simple loudspeaker protection circuit?

2. I am helping my friend build a 4 channel amp with opa549's..a chip per channel. and he has a big 550va EI trafo.. with 22-0-22.. thats about 31vdc+/-.. and 549's are 30vdc+/- max.. so can i run 4 of them off 1 trafo.. with rail voltage of 31vdc+/-? wont there be any voltage loss on the rails with 4 chips?

Ad. 2:

You are just over the limit - just. If you dare you could try and use it. No garantees, but it might work.

Furthermore, if the transformer is not loaded it gives out higher voltage than rated. If I were you I would find out how big a load your 4 amps are (no signal) with a smaller transformer, and then calculate a resistor as test load on the wanted transformer, and then see how big a voltage it gives. Or as a pointer; test with a 2Kohm resistor.

Using one diode bridge per voltage side will help, but is it enough?
Hi Again,
I have started to build the LS protection circuit, and i saw somthing stange in the circuit:
The "-" leads of both 47uF caps and connected, and 1 "+" lead is connected to ground, and the 2nd "+" lead is connected to 22k resistors....
Is this right, or is it a mistake that wasn't noticed?
Here is the like to the schematic:
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