Generating 48V@50mA from 5V for microphone phantom power...

[Allan Herriman]

It's possibly a bad idea to use 1/2W resistors, as these aren't
usually available in the close tolerances required. The match (but
not the actual value) of the two resistances needs to be very
accurate.

It is possible to make up the desired power rating by using a number
of lower powered precision resistors in parallel or series.

.... if anyone knows of a source of matched 6.8kohm 1/2W resistors,
please let us know.

 

[Fred Bloggs]

... if anyone knows of a source of matched 6.8kohm 1/2W resistors,
please let us know.

http://www.vishay.com/docs/63006/hmetlab.pdf also available in
multi-resistor SIP with these power ratings. There is ceramic line too.