Zen I/V Converter

[jbercovici]

Hi, I'm new on this thread. Does anyone have a complete BOM, scheme and PCB layout (I/V and power supply) for a Buffalo IIISE output stage.
Julien

[R-K Rønningstad]

Originally Posted by didiet78

Not yet. I dont have Iout DAC. My DAC ESS9023.

Didiet

The Zen I/V is of course designed for current output DACs. I wonder, how many current output DACs are in use today? If one would like to upgrade a CD/DVD/BR-player or even a DAC, does not these often have voltage output DACs, with built-in op-amps?
If you would like to roll your own, you have maybe the Buffalo DAC or the QNKTC DAC. Then there is use for something like the Zen I/V.

/RK

[Ken Newton]

Originally Posted by R-K Rønningstad

The Zen I/V is of course designed for current output DACs. I wonder, how many current output DACs are in use today?

The best DAC chips from T.I. (Former Burr-Brown), Analog Devices, and ESS Tech feature current outputs. Namely, the PCM179x series, the AD1853 and AD1955, and (I believe) the Sabre32 Reference DACs. In addition, the 24-bit PCM1704 is a current output device. There are as many 'top model' DAC chips featuring current outputs as such DACs featuring voltage outputs. The main vendors offering 'top model' voltage output DAC chips are, Cirrus, Wolfson, and AKM.

[R-K Rønningstad]

Thank you, Ken.
I haven't followed the DAC chips too well lately, I understand.

/RK

[jbercovici]

Yes, ESS Sabre can work on v or I output. I'll choose current output with the zen I/V, but does anyone have a complete BOM, scheme and PCB layout (I/V and power supply) for a Buffalo IIISE output stage ?
Julien

[R-K Rønningstad]

Consider e.g. Texas Instruments DSD1794 (attached). This can accept DSD and flavours of PCM up to 192 kHz. Figures 33 and 34 shows analogue filters for PCM, while figure 35 shows an analogue filter application for DSD. The I/V part can of course be realized with the Zen I/V, while the output could be realized with a simple JFET based opamp, se picture.
However, for DSD, it is recommended a low cut of frequency, while for PCM a much higher is recommended.
This means that most likely, the same analogue stage is not optimum for both DSD and PCM.

/RK

[Ken Newton]

Originally Posted by R-K Rønningstad

Consider e.g. Texas Instruments DSD1794 (attached). This can accept DSD and flavours of PCM up to 192 kHz. Figures 33 and 34 shows analogue filters for PCM, while figure 35 shows an analogue filter application for DSD. The I/V part can of course be realized with the Zen I/V...

A complication arises when utilizing a current output DAC which does not feature an internal output bias offset correcting current-source. These DACs, such as the PCM179x series, ad the AD1955, will either sink or source a D.C. bias current from their output pins. This current must be accounted for by the I/V stage in terms of it's affect on THD, and on eventual D.C. output voltage offset. For example, the DSD1794 needs to source 6.2mA of D.C. bias current in to the I/V circuit in addition the 3.9mA peak signal current. This is a 10.1mA maximum sum, which could easily produce significant amounts of distortion in a relatively low bias zero-feedback circuit, such as the JFET based Zen I/V. As a very general rule-of-thumb, open-loop grounded gate/base type I/V circuits seem to perform best with a quiescent bias current roughly 10 times the peak signal current.