PSU with +-20V or +-22V Regulated from 18V AC transformer ?

Is it possible to get these regulated voltages from a 18V AC transformer operating without any problems ? Need it for a preamp and i have an external transformer i would like to use if possible (center tapped, 2 * 18V AC, 1.4A).

Don't know how much current i need yet but at least a lot less than 50% of that.
 
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Yes this is possible. The VRDN dual regulated power supply board here on the Forums, shows one way how. This type of circuit can accept either a single secondary transformer (like an AC wall wart) with two secondary wires, or a dual secondary transformer with four secondary wires. But not a "center tapped" transformer with three secondary wires. VRDN's voltage outputs are adjustable from ±11V to ±20V , max current is 1 ampere per side. LINK .
 
Yes this is possible. The VRDN dual regulated power supply board here on the Forums, shows one way how. This type of circuit can accept either a single secondary transformer (like an AC wall wart) with two secondary wires, or a dual secondary transformer with four secondary wires. But not a "center tapped" transformer with three secondary wires. VRDN's voltage outputs are adjustable from ±11V to ±20V , max current is 1 ampere per side. LINK .
The transformer i have is center tapped.
 
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It is possible, yes. Is there a pre-made printed circuit board that you can buy, which implements one of the possible solutions? I personally don't know of one, but it is certainly possible that one or more might exist. OR you can just engineer your own and then offer it for sale {or free !!} to others.

The problem is that center tapped transformer circuits are, more often than not, "wasteful". The cost savings versus dual secondary transformer circuits are negligibly small, but CT circuits generally create twice the output ripple (noise). So for the same money you get half the performance. Ick.
 
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I wrote that in the first post, i might have missed something


Transformer out: center tapped, 2 * 18V AC, 2 * 1.4A

Requested DC out: +- 20v DC or +- 22V DC.

Load less than: 600 mA per DC output. + and -.
ok, 18-0-18 in FWB gives you 50vdc unloaded, split that and you get + - 25vdc your regulator must be low dropout type as you only have 3 volts to work with...switching dc to dc regulator will work best for you unless you are willing to go + -15 volts dc..
 
Thanks for the info so far everyone. I will do my own PCB for this that will make things a little easier than trying to find one to buy.

So if i chose +-20V DC i can base it on LM317/LM317 and it will be ok ?

And if i chose +-22V i need better regulators with lower droput to avoid possible "problems" ? Any suggestions what to use ?
 
@chrisng

I never used this approach in a PSU before, so i don't know if there is any "problems" with it. I have the space for it is so if this works ok it might be an option. Do you know any example of it and what type of transformer to use. I can use higher than +-22V DC out so higher voltage is not a problem.