How do I connect a current output DAC to I/V stage single ended

[Thermosphere]

Hi,
I have an PCM1798 based DAC which has a passive I/V output stage and I am not very liked it. I want to try the new Zen JFET-based I/V stage and I have a (possibly very easy and dumb) question.

As you know the PCM1798 has differantial current outputs for each channel: IOUT(R/L)+ and IOUT(R/L)- . The Zen I/V has only one input. How can I connect these together to provide an unbalanced output?
I think I must connect the IOUT+ to Zen input and IOUT- to GND. Because I'm not very experienced these kind of circuits, I wanted to sure about this.

Thanks.

 

[SemperFi]

I did it like this, passive conversion. The DAC don't like large voltage swings, and the 50ohm resistors are a good match. The transformer is a Lundahl. Sounds pretty damn good

The output level is lower than redbook standard, but thats a good thing because you can crank the preamp volume, which means less wiper in the path.

 

[SemperFi]

Like this that is:

 

[SemperFi]

Hmm, something is playing with me, cant seem to get the schem up. Perhaps I saved it in the wrong format....
Trying a jpeg.

 

[jcx]

or use 2 Zen, diff to single ended with xfmr: ( from http://www.diyaudio.com/forums/digi...radeoff-run-dac-single-ended.html#post2306210 )

 

[Sandor]

The should be almost no voltage between the drains of J1 and J3. Maybe the output capacitors may be omitted.

 

[DougL]

The should be almost no voltage between the drains of J1 and J3

True, but there is 30V between the drain of J1 and J2. While there are ways around it, juts removing the caps will not work.

 

[SemperFi]

And why do u want all that in the signal path when one resistor per phase is aplenty?

 

[qusp]

because 1 resistor is IMO and many other opinion, NOT PLENTY. you do not gain the best performance from the dac this way. current out dacs often prefer to operate into very low impedance and preferably with their outputs returned to a virtual ground biased to AVCC/2

 

[Irakli]

because 1 resistor is IMO and many other opinion, NOT PLENTY. you do not gain the best performance from the dac this way. current out dacs often prefer to operate into very low impedance and preferably with their outputs returned to a virtual ground biased to AVCC/2

I agree about low impedance, but what is gained by biasing virtual ground to AVCC/2 ?

 

[SemperFi]

because 1 resistor is IMO and many other opinion, NOT PLENTY. you do not gain the best performance from the dac this way. current out dacs often prefer to operate into very low impedance and preferably with their outputs returned to a virtual ground biased to AVCC/2

Well, with a passive solution and an output transformer, you can make the return anywhere u like. 50 ohms is low enuff, the DAC stays linear and has plenty complience.
The only issue is the lower than standard output level, but that to me is a good thing since I can set the volume potentiometer higher, which leaves less in the way. I have never had problems with playing loud enough, in fact the level is more like my phono pre, and I can pretty much leave the volume when switching between the two.
The benefits of a good transformer is also a choice of SE or BAL output, as well as preventing ground loops.