Phantom power help needed !

[MartyMart]

Hi chaps, I've searched and found lots of info here but many threads have led to "dead" links or circuit versions that won't apply to my required circuit and parts that I have.
Here's what I need to build and also what I have available :

I need a simple clean 48v dc phantom supply to add to a pair of V676 TF mic amps.
I have the 24v dc supply in a rack with one V676 and will be adding a second unit.
There's plenty of space in there for a separate phantom supply board.
I have about 5 traffo's all new, a couple are 240v to 15v and one has a dual 15v secondary, ratings are 3.2VA and 1.7VA .
LM317's and other parts I have also.
Is it possible to simply join the dual 15v supply's to get 30v ac and regulate/filter from there ?
Any tips on this much appreciated.
Marty

 

[okgb]

SSL Keith , has a psu circuit for the 9K and you can take the 48v section from there , not many parts .
It would seem the easiest and most straightforward method to get the 48v
however would be having at least 40 vac feeding the separate bridge rectifier to the phantom .
Run a voltage doubler from your secondary ac of the 24 v supply ?
eats up a little more current , but can it be done at the same time as
a bridge rectifier running off the same ac ?

Could be a good question for retrofits , any smarter opinions ?

 

[MartyMart]

Thanks, I thought of doing that but was advised not to "pinch" my supply from that section and to have a separate unit for the 48v supply.
Just trying to use up one of the dual 15v traffo's that I have ...
MM

 

[okgb]

if you have a separate 15-15 ac out xfmr , you could triple one of the windings with the smoothing caps that should get you there , just
need to calulate the current lose through the tripler and the draw from the phantom [ which shouldn't be much ]

Need someone smarter than me to say if wiring the secondaries in
paralell would help for current draw , otherwise one of the secondary
to center tap for 15 v , use a voltage tripler [ a reasonable idea ? ]
and proceed to phantom circuit , anyone ?

 

[SSLtech]

15VAC voltage-tripled/rectified will give you about fifty-something volts (after tax) unregulated. Send that into the LM317 regulator section of the SSLtech 48V rail, and you'll get a nice 48V output.

Add the caps to the circuit, as discussed in the 'noisy phantom rail' thread...

Keith

 

[okgb]

Keith , would it be of any practical benefit to use both of the
secondary windings for greater current " headroom " ?
that works if you paralell them ?
or no they have to be separate windings not just centered tapped
so they don't cancel