[sdiy] Semi-OT: phantom-powered balanced line driver?

[René Schmitz]

Magnus Danielson wrote:

>>>But that's me.
>>
>>Me too. Takeing the voltage with a center tap is a snap, even if you 
>>don't have that, you can get the supply voltage at a virtual center, the 
>>mid of two resistors from either side.
> 
> 
> You DONT want to do that for power, please! Brr...
> 
> But OK, if you don't consume that much current you could do that, but it feels
> soo ugly. It goes into my book of ugly quick-hacks.

I recall that the phantom power is applied like that on the desk end.
In my "Handbuch der Tonstudiotechnik" it states to use 2x6.8k matched 
0.1% to 48V and _not_ to use a center tap, simply to avoid magnetizing 
the core due to slight mismatches in the windings. This keeps the 
current through the winding at zero. Doesn't hurt doing that on the 
other end as well.
The phantom power is current limited and rather high Z anyway.
A pair of 2k2-6k8 or so won't add much on the bill. And you need a much 
lower voltage anyway, so you can add some stabilizing means.

> Besides, it always feels good to do it properly the good old way! ;O)

Which I still consider state of the art.

Cheers,
  René


-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159