Deskamp power supply schematic.

I threw together this schematic in Eagle in order to keep an organized idea of what I wanted to accomplish as I get ready to make a more complicated and better sounding desktop headphone amplifier.

I'm not interested in putting batteries in it at all, so I wanted to make sure that this was the proper way to use the LM317 to regulate a DC walwart and then split it into two rails.  I used the datasheet for the LM317 and Tangent's guide on splitting rails to draw this up.  It's basically just a copy, I'm sure, of what Tangent had on there with the DC jack and LM317 stuck on there.

By the looks of it, I may have gotten confused about what pin on the jack was positive in Eagle, so assume that the pin leading into the 317 is the positive pin.

I'm not looking to make this a perfect regulator, I just want a regulated supply voltage that is split in a reliable and clean enough way to provide an upgrade to two 9v batteries.  The goal is to supply the op-amps with 30v of regulated power.  I planned to pick up a 40v walwart.

I am most unsure of how the pinout on the DC jack works.  If I have that setup correctly for the rail split.  If anyone could tell me if there are any really glaring mistakes here, I would appreciate it.

Thanks in advance.

EDIT: I'm sorry for any issues with the readability of the schematic or if parts aren't necessarily what they should be... I did my best, but this was my first time with the program.

-Robert

I chose to do a single rail, rail-splitter, power supply in order to keep things within my realm of understanding for now.  I was pushing it with my application of the LM317.  Attempting to do a dual rail system from AC with a rectifier would have been slightly outside that envelope at the moment.  I'm taking baby steps up from the CMoy.

Heck, I was planning on connecting this to an amp barely more complicated than a CMoy.  I still have a lot of reading to do before I work on the amp, though.

Screw it, though.  I guess I will just go with the center-tapped AC route.  The rectifier is easy and all it really seems to be is the addition of an LM337 on the negative rail.

I'd be all for building the circuit you posted, Avro, just one question... what are those KK1 SK129-PADs?  How do they connect to the circuit?

The kind of walwart I will need to look for is a center-tapped AC, right?  Or would it just be called grounded AC?  Not 100% on it.

Thank you all for the posts and suggestions.

-Robert

EDIT: Looking at the datasheet for the LM337, I have another question.  In your dual rail schematic up there you put the LM337 right on the negative rail.  In reference to the positive rail, the negative is currently actually at 0v, right?  So if I have a 40v AC walwart then the positive rail would be 40v and the negative 0v in reference to each other.  However the positive becomes 20v in reference to the new ground between them and the negative becomes -20v in reference to the ground between them.  If I am correct in saying that, then this is also a "virtual ground" right?

What step is taken from there to make an active ground?  (Probably getting ahead of myself here.)

OK, I hadn't really considered putting the transformer in the case itself... might need to invest in a new case.  haha  Anyway, what kind of power cord would I need to get to get wall power to those transformers?  Would it use a standard 2 or 3 pronged power cord like what you might see from a computer power supply or monitor power supply?

AH!  Ok, I see.  Now using a board mounted transformer seems to be a bit of a waste of board space, so using a chassis mounted one seems more economical.  Now you posted that particular one and suggested it would be enough, I had been aiming for a 40v so that I would have enough to supply the rail splitters to ensure that I could get a +15v rail and a -15v rail so that I would be in a good healthy upper range for the op-amp down the road in the circuit.

The one you suggested is 25v total, so 12.5v split between each rail, right?

Is there an advantage to staying at a lower voltage?  (Coming from computer tweaking, I had thought more voltage without going overboard would aid in stability and performance.)  I have heard that the idea performance voltage will differ from op-amp to op-amp, so not really sure where I should take it.

I had planned to get the 40v from the transformer and use resisters on the regulators to reduce voltage down to desired levels (taking the 40v to the +-15v I desired.)  But I am using 600ohm headphones, so if higher voltage might be needed for that, then it's something to consider.

So if I am using a total of 40v before the regulator, then I need caps that are rated for 80v, to be safe?

I'm not too worried about heat, per se.  These heatsinks seem pretty beefy and should be able to handle whatever is needed.  Worst comes to worst I can always wire a fan into the chassis.  (thinking about using an old PS2 case for this.)

The caps I have already picked are only 50v but if I wire them up past the regulators, shouldn't that be ok?  I could keep a couple lesser quality electrolytics before the regulators and then have the bulk of my capacitance on the output?