low pass filter for DSD

In order to get the best values for R and C we'd need to know the leakage inductance of the transformer. Since that's not shown in the Sowter datasheet you could either measure it (needs an inductance meter) or you could just try 680ohm and 100nF and see what happens.

What have I to look after putting 680ohm and 100nF in the secondary? I guess using my scope, but what have I to look for and what scope scales?
 
Asked the information to Sowter. Now time to play with the scope looking for the best squarewave @ 1kHz, thanks abraxalito.

Attached pics of scope, one direct to SG and the other to the 100K dummy load, finally resistor 3k61 so I will use standard resistor 3K6.

It's necessary the output coupling capacitor after the 1:1 transformer?

It's magic, no cliks or pops changing between PCM & DSD. I still need the output capacitor to avoid DC: I have AVC at the input of preamp or headphone amp and don't likes DC, I listen scratches when I turn the volume.
 

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Very clean looking squarewave, nice job! I don't think you need a capacitor after the trafo but certainly it needs one before it. Its impossible for DC to come out from a trafo.


Incidentally, 10uF is too low for a 600ohm trafo, I think you'd better go up to at least 470uF.
 
Forgot to attach the schematic.

Finally used two caps 220uF 16V BG. Always can increase capacitance adding one more 220UF 16V in parallel.
 

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The primary inductance of the trafo forms a resonance with the coupling cap. A high enough value cap keeps the resonance well below audio frequencies. If you decrease the cap you'll move the resonance (a bump in the FR) upwards in freq so will end up with more bass. If you keep reducing the cap the bump will move into the mid range eventually and the bass will roll off prematurely.