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

Thermosphere · 22nd September 2010, 07:58 PM

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 · 08:46 PM

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 · 22nd September 2010, 08:47 PM

Like this that is:

SemperFi · 22nd September 2010, 08:49 PM

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 · 10:42 PM

or use 2 Zen, diff to single ended with xfmr: ( from What is the tradeoff to run a DAC single ended? )

Sandor · 23rd September 2010, 12:27 PM

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

DougL · 05:32 PM

Quote:

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 · 23rd September 2010, 06:12 PM

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

qusp · 25th September 2010, 05:03 AM

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 · 25th September 2010, 05:44 AM

Quote:

Originally Posted by 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

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

22nd September 2010, 07:58 PM	#1
Thermosphere diyAudio Member Join Date: Sep 2010	How do I connect a current output DAC to I/V stage single ended 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.

22nd September 2010, 08:44 PM	#2
SemperFi diyAudio Member Join Date: Jan 2002 Location: nowhere	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. Last edited by SemperFi; 22nd September 2010 at 08:46 PM. Reason: forgot the schematic:)

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
URL collection of Totem Pole and CSPP (Single Ended related) Solid State Output Stage	tiefbassuebertr	Solid State	7	10th May 2012 05:02 PM
What is the tradeoff to run a DAC single ended?	DougL	Digital Line Level	13	11th October 2010 06:51 PM
How does the current source work in a single-ended amp ?	tessier	Pass Labs	1	4th September 2010 08:39 AM
WTB: Single Ended Output Transformers	Zedguy	Swap Meet	2	2nd August 2009 02:05 AM
Anyone play with the Zen Single-Stage Single-Ended Class A?	Rino odorico	Pass Labs	13	29th August 2002 09:01 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

22nd September 2010, 08:47 PM	#3
SemperFi diyAudio Member Join Date: Jan 2002 Location: nowhere	Like this that is:

23rd September 2010, 12:27 PM	#6
Sandor diyAudio Member Join Date: Mar 2004 Location: Milan	The should be almost no voltage between the drains of J1 and J3. Maybe the output capacitors may be omitted.

23rd September 2010, 06:12 PM	#8
SemperFi diyAudio Member Join Date: Jan 2002 Location: nowhere	And why do u want all that in the signal path when one resistor per phase is aplenty?

25th September 2010, 05:03 AM	#9
qusp Sometimes a square peg fits a round hole just fine diyAudio Member Join Date: Oct 2009 Location: Brisbane, Australia	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

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)