TDA1541 IV Conversion - Circuit Help Needed

[kblsnbts]

I would like to build the IV conversion circuit described at the following web site:

http://ultranalog.com/cdenhancer/cdenhancer1.html

The DAC appears to be connected to the analog circuit using a 1 volt source between the digital ground and analog ground, the idea being that the DAC sees 0V.

But what is this 1V source? It appears to be a battery symbol, but I don't believe the circuit would function with a battery connecting the analog to digital ground.

Can someone please elaborate on what this voltage source might be?

Thanks!

[wa2ise]

All you'd really need is a power supply that produces clean -1V to feed the bottom of the 100 ohm resistor. Using the AC heater supply thru a rectifier diode and then filter cap and then a voltage regulator (one made to do negative supplies) would do it. Subsequent analog stages won't need to run off this -1V supply, but can use the same voltage as the digital ground.