Metrum Pavane NOS DAC

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

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.

George, note that A1 is configured as a unity gain buffer, not as an I/V converter, and that it is not even in the path to Vout. Its purpose, as shown on pages 24 and 25 (pdf pages 25 and 26) of the datasheet, is to support a number of different configurations of the external buffer or other amplifier that would be driven by Vout.

Regards,
-- Al

So are you saying Al that this dac is a real R2R Ladder Multibit dac, that can output volts even though it's high impedance (rather than being current output) with no I/V stage involved?

Cheers George

Yes, that appears to be the case as far as I can tell from the datasheet, George. With the slight qualification that while the D/A conversion is accomplished by a resistor ladder, strictly speaking it's not an R2R ladder (see page 19, pdf page 20, of the datasheet).

We'll see if Ric can obtain confirmation of that when he calls Analog Devices. But as he indicated, that interpretation is given added credibility by the fact that TotalDAC and MSB Technology, which use R2R ladder approaches (albeit with discrete resistors, and at vastly higher price points, and with at least several additional bits worth of performance), also do not require or incorporate I/V conversion.

Regards,
-- Al