power supply ?

[donivan]

A rookie question about phantom
I'm racking up 2 mpc 500 mic pres that require +/_ 24vdc
could I not use the outside rails of that supply for 48vdc for the phantom supply?
or would that just be an easy way of getting out of your contract with your vocalist (no ground reference?)
also there is an 8vac leg on the secondary of the power transformer
could I not use that for the 6.3vac meter lamps?

I know these are amateur questions
but I knoiw just enough electronics to be a danger to myself and others

thanks for any help

 

[dmp]

The +/- 24 has a ground at 0v. For the phantom to be 48v, the -24v would have to be tied to ground. You can't tie 0v and -24v to ground without shorting out the -24v.
So you need a dedicated 48v supply. There are cheap small stand alone PSUs like this
The ground of that 48v supply would go to pin 1 of the XLR, which would also go to the case, which is also connected to the 0v +/-24v PSU

You can use the 8vAC winding just put in a dropping resistor before the lamps. Figure out the total lamp current. Then the R=V/I
Make sure the secondary is rated for sufficient current you want to supply.

 

[donivan]

The +/- 24 has a ground at 0v. For the phantom to be 48v, the -24v would have to be tied to ground. You can't tie 0v and -24v to ground without shorting out the -24v.
So you need a dedicated 48v supply. There are cheap small stand alone PSUs like this
The ground of that 48v supply would go to pin 1 of the XLR, which would also go to the case, which is also connected to the 0v +/-24v PSU

You can use the 8vAC winding just put in a dropping resistor before the lamps. Figure out the total lamp current. Then the R=V/I
Make sure the secondary is rated for sufficient current you want to supply.

got it
thanks