Simulation of I/U (I/V) converter versions for TI PCM R2R DAC's (e.g. PCM1704) ?"

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Sorry to correct you Sonnya, but using a current source will NOT simulate a true PCM1704 or similiar output.
Check page 2 in the PCM1704 datasheet: PCM1704 Datasheet
Find the "Analog Output" section... Here it says that the output current is 1.2mA and the output impedance is 1kohm. Since this is a "current generator", the output impedance should med simulated by using a 1.2mA current source in parallel with a 1kohm resistor.

By doing this, you will notice why the input impedance of the I/V converter is so critical. If you have a 1kohm input impedance, only half of the signal strength will go into the I/V converter, while the rest is blown away inside the PCM1704.
But it gets worse. Since the input impedance will most likely be non-linear, you will have a non-linear transfer between the PCM1704 and the I/V converter. The lower the input impedance, the less critical the non-linarities of the impedance will be. The difference in signal-energy transferred will be less, since almost all the energy is transferred at low impedances.
This really is one of the main reasons why you must ALWAYS use a low impedance I/V converter for critical applications.

The other reason is, that a high impedance input will result in voltage changes along with the music signal. And that will cause non-linarities inside the DAC-circuit.

So again! Use a low impedance input I/V-converter, and remember the paralell resistor at the current source when simulating.
 
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