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-   -   which transformer to use for this regulated supply? (http://www.diyaudio.com/forums/power-supplies/236573-transformer-use-regulated-supply.html)

godslayer 25th May 2013 03:55 PM

which transformer to use for this regulated supply?
 
Hi guys,

while stumbling over the internet looking for +-15v good regulated supply using 317/337 i stumbled upon this link which i chose for the construction of my supply as this is the easiest no frills +-15v schematic i can ever get

http://audio.gotroot.ca/minipow/

i havent been able to find the transformer rating. can someone help me with that? will 12-0-12@ >25VA work fine with this?

does someone have a BETTER and simpler circuit for a clean +-15v than this?

Rundmaus 25th May 2013 04:12 PM

I don't see the point of so much filter capacitance before the regulator. Otherwise, it seems pretty standard as shown in the 317 application note.

Rundmaus

Rundmaus 25th May 2013 04:31 PM

... just noticed that I did not really answer your question.

12VAC will give approx. 18VDC rectified, minus the voltage drop of two diodes (1.4V). This does not leave enough headroom for the regulator, especially with some mains variations, IMHO.

LM337 is capable of 1.5A, I seem to remember, better check it in the datasheet. So the maximum sensible current draw is 1.5A per rail, meaning 30V*1.5A = 45W. I would use at least 50-70VA transformer, unless you definitely know you will not be drawing that much current.

Rundmaus

godslayer 25th May 2013 04:41 PM

i wont be drawing much current, i just need the supply for p88 (esp) and one bass filter cutoff ie all in all driving 4 opamps... ill go for higher one, maybe 15-0-15 @ 2a(60va) thanks for the help :)

as for the complications you mentioned, will this circuit work? given that i use only 15v network? is it suitable enough for Audio application(i see varied register networks than previous circuit)?

http://www.eleccircuit.com/wp-conten...lm317lm337.jpg

AndrewT 25th May 2013 06:04 PM

15+15Vac is perfect for a regulated 15+15Vdc

godslayer 25th May 2013 06:31 PM

Quote:

Originally Posted by AndrewT (Post 3504359)
15+15Vac is perfect for a regulated 15+15Vdc

can i also have your critique on the above circuit?

AndrewT 26th May 2013 07:37 AM

LED5 is being run very hard
R38 might be a bit high.
The switching is going to send ~23V pulses to the outputs.
C1, 2, 9 & 10 are shown in the wrong locations.
The continuous Zero Volts wire from chassis to GND is wrong.

AJT 26th May 2013 09:29 AM

Quote:

Originally Posted by AndrewT (Post 3504359)
15+15Vac is perfect for a regulated 15+15Vdc

yes, but down to 3 volts out your regulator is wasting most of the power...

godslayer 26th May 2013 05:48 PM

Quote:

Originally Posted by Tony (Post 3504937)
yes, but down to 3 volts out your regulator is wasting most of the power...

i have a spare 13-0-13v @ 75va one lying in my drawer. i guess that will be perfect.

26v-> 36vdc minus the diode drop
2a-> 1.27A dc

36v dc 3v for each regulator to regulate. i guess things are better like this.

i will go with minipow supply then.

sofaspud 26th May 2013 07:14 PM

Quote:

Originally Posted by AndrewT (Post 3504855)
LED5 is being run very hard
R38 might be a bit high.

Typo?
Looks like the LED receives ~15mA; R38 could probably be increased in value.
Quote:

Originally Posted by Tony (Post 3504937)
yes, but down to 3 volts out your regulator is wasting most of the power...

Maybe not "most of the power," but more than necessary.
For a handful of op amps, either the 26VCT or 30VCT transformers should be more than big enough.


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