+15v, +9V and -9v from one PSU?

[Jaicen_solo]

I was thinking about producing these voltages for use in my 'Jimi in a Box.'
I'm part way through the project, and while I was waiting for my SB order (arrived today, thanks Steve!), I began working on my Fuzz Faces.
I have a bag full of AC167's and 128's, which I went through testing last night. Most of the AC167's are too leaky to use, as are many of the 128's.
I do have a handful of 128's that I can use however, therefore I was wondering if I can get the voltage for this from my 15-0-15v transformer.
Can I rectify the AC seperately, and run it to three different Regulators to get +9v, -9v and +15v, without having grounding issues?
That way I can use an original PNP circuit in the box, instead of an NPN/hybrid thing.

[smallbearelec]

wondering if I can get the voltage for this from my 15-0-15v transformer.
Can I rectify the AC seperately, and run it to three different Regulators to get +9v, -9v and +15v, without having grounding issues?

You can get +9 and -9 no problem, and there are plenty of schems out there for doing this. But to get +15, you would want the transformer input to be rated 18 Volts or so so that the regulation works correctly.

[Jaicen_solo]

Thanks Steve, i'll google it and see if I can turn anything up.
The transformer I have is 30VAC centertapped, i'm only using one of the secondaries and the center. After it's rectified and filtered by the 1000uF caps on the Neovibe board, that comes out at something like 22v, and gves me a steady 15v after the regulator, so that's just fine.
Is there any need to use the -'ve tap to get the -9v, or should I just use the single 15vAC tap, and send that to three rectifiers?

[Gus]

You can get +15 from lower AC voltage transformers.  Look up doubler circuits.

look at the PS section of this PDF for ideas, note how the 48VDC is generated.
http://www.studio21.ch/diy/neeno/ssl9k/DIY_9k_Preamp.pdf

Now you will need to look up understand VA rating

[nick d]

                  You've got the +15V , use a 7809 reg to give the +9V , use the other tap with another rectifier/smoothing circuit and a 7909 to get the -9V . Have a look at some synth supply schemos for details , Ken Stone is pretty good .

[Jaicen_solo]

That's actually what I was planning to do, but then it occured to me that I would be able to get the same result using one 15vAC tap, and two rectifiers. That would give me two seperate DC rails which I could wire as + and -.
Is there any real advantage to using the second tap though?

[nick d]

                    I may be wrong , but think you DO need the 2nd tap to get the -ve supply .

[nick d]

                 I stand slightly corrected - you do need both taps plus the centre tap to get +/- / the centre tap being ground , but only one bridge rectifier is needed .
                 I have a suitable schemo but I haven't figured out how to post pictures on here yet . (super-noob ! )
                 Have a look at the guy I mentioned , or try Experimentalistsanonymous  or Music From Outer Space . Best to get it right with mains !

[PRR]

> one 15vAC tap, and two rectifiers. That would give me two seperate DC rails

No. They will be "stuck together". Try it.

TWO WINDINGS and two rectifiers will give two separate DC sources, which may be wired for whatever polarity.

One _CT_ winding and one FWB rectifier, CT called "common", gives +22V and -22V relative to "common", which can give you the rails you want.

[PRR]

> how to post pictures on here yet.

There is not an in-posting image attachment feature.

There is a Gallery for long-term storage.

For quick-picks, there is another way. Put your image in any public image-hosting site. There are several/many. I like TinyPic.com because it is low-hassle and you can post without registering. (Of course this means ads.)



Grab the code and paste into a forum post.