Isomagic w transformers in amplifier

[TomasF]

Hi
my next project might give extrordinary results, please help me identify the pitfalls!

At home I run a modified Cambridge Isomagic (S700) feeding a power amplifier. Toslink. Clock Lock. Passive volume control.

My idea for next project is to integrate the Isomagic DAC board into the power amplifier. In the amplifier I have only DC (fed from separate box power supply) so there will not be much 50 Hz AC disturbing the DAC operation. I can in the amp easily obtain +5V that I need for Isomagic digital section (or keep todays solution with batteries). The DAC chip will feed into a Lundahl transformer (1:10 or so, I live near their factory) and connect to the volume control. Connection for digital in and Clock Lock would be optical directly into the power amp.

Benefits:
Two opamps less to travel.
No signal cable to travel.
One capacitor less to travel (Isomagic have after mod a lot DC on output).
No power supply needed to opamps (+-15 V supply weak spot in Isomagic)

What specifications do I need for the transformer?
Do I need a resistor to ground as some is using or do I just connect the transformer to two outputs on the DAC?
If I power Isomagic with only +5V (or rather low noise +12 V regulated down to +5V) will the whole digital section inkl HDCD work?

All comments are appreciated. / BR Tomas Fridstrom