The AD5791 datasheet describes it as providing a voltage output, but one that is unbuffered, and that has a high nominal output impedance of 3.4K. So when used in a DAC component it would almost certainly require a separate buffer stage, and as Ric indicated it is very conceivable that its voltage output is driven directly from the resistor network. Regards, -- Al |
Sorry Al Separate Buffer? or separate I/V then buffer?? Correct me if I'm wrong. As from what I saw there were no current (mA) output figures given for it's output, which all manufactures give for current output dacs. Also Look at page 26 Positive input to the opamp, and no grounding of the negative. Now look at the page 9 of the PCM1704 I/V stage neg input with grounding of the positive for low impedance input. Same for what I've seen for most current output dacs on data sheets. http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&sqi=2&ved=0CCQQFjABahUKEwiixfXOwqzHAhWlqqYKHRcmAYI&url=http%3A%2F%2Fwww.ti.com%2Flit%2Fds%2Fsymlink%2Fpcm1704.pdf&ei=p_DPVeLVNKXVmgWXzISQCA&usg=AFQjCNEK5ScUy3tujTC6njrwwvKnluukTg&bvm=bv.99804247,d.dGY Cheers George |
George, As I described earlier it is possible to make an R2R DAC that has voltage out and not current out. This is what TotalDAC has and so does MSB. They do not need IV conversion. Maybe the 5791 does the same. The amount of voltage out on the 5791 is determined by the power supply voltages you use on the DAC. The Yggdrasil actually puts out 4.6VRMS out of each DAC chip (4.6V per phase). This was just measured on an Yggy today. There is no measureable DC offset on the output of the DACs. The voltage coming out of the output stage buffers is 2VRMS per phase so the buffers actually lower the voltage coming out of the DAC. I will call Analog Devices on Monday and ask them if there is a built in IV converter.....I don't think so. Anyway, the stock Yggy sounds great and the modded one sound way better and now I will be putting my zero feedback fet buffer on the output instead of the Schiit stage and see what we get....fun times ahead. |
I don't understand your post, George. I think we're both agreed that the AD5791 provides a voltage output, as the datasheet plainly says in numerous places. But it has a very high output impedance, and as Ric indicated it seems very conceivable that the voltage is directly generated by the resistor network. Rather than via an internal active stage that would perform an I/V conversion. Although without further information we can't say that with complete certainty. Also, I don't see the relevance of your reference to the PCM1704. The stage (U1) you referred to on page 9 of the PCM1704 datasheet is, as you said, an I/V converter. While the stage (U6) you referred to on page 26 of the AD5791 datasheet is a unity gain buffer configuration, which would provide an output voltage closely matching its input voltage. Regards, -- Al |
Sorry Al, I misunderstood your post. As to no experimentation with any I/V stages, as I originally posted with this dac. As great leaps have been made with I/V stages (away from the norm) and this dac doesn't allow this. As it would have standard text book I/V embedded within the dac itself which looks to be A1 on the data sheet, but with high output impedance. That's all Cheers George |
