Characteristic impedance for the filter should match the output impedance of your DAC. Do you know what that is? (In the schematic I've shown, its 195ohms).
You can transform my schematic fairly simply to any characteristic impedance - for impedances higher than 195R just multiply the inductors and divide the caps values by the ratio of the new impedance to 195R.
<edit> No it can't work without a DAC, but the DAC can be very simple as it only needs to be 1bit for DSD. You will need to pay attention to jitter though unless the DAC is a charge-dumping (e.g. switched capacitor) kind. Trying to use just a logic gate would mean the challenge of low enough jitter would be a tough nut to crack.
You can transform my schematic fairly simply to any characteristic impedance - for impedances higher than 195R just multiply the inductors and divide the caps values by the ratio of the new impedance to 195R.
<edit> No it can't work without a DAC, but the DAC can be very simple as it only needs to be 1bit for DSD. You will need to pay attention to jitter though unless the DAC is a charge-dumping (e.g. switched capacitor) kind. Trying to use just a logic gate would mean the challenge of low enough jitter would be a tough nut to crack.
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I want to filter and amplify the DSD signal directly from the Amanero USB-I2S device.
http://www.lampizator.eu/NEWDAC/Lampizator/DSD_DAC.html
http://www.lampizator.eu/NEWDAC/Lampizator/DSD_DAC.html
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So that's presumably a logic gate giving the output. Do you have a schematic? The output impedance will depend on the particular gate (or perhaps FPGA) providing the output signal. If you use that signal directly you'll find your design will be inordinately jitter-sensitive but you'll still get sound out.
Well, even the lampizator device is a DAC, even if a minimal one - you can't use the raw I2S output as an analog signal (at least if you expect the result to be music). I think you were right with your first comment:
By the way, if you go ahead, remember the advice from Lampizator:
🙂
I am sorry, but you choose to ignore my slightly more diplomatic earlier comment:
You are asking us to design your system for you, but get offended when we tell you it is not a very good idea in the first place...
Had a look, could not see any DSD outputs marked. Assume the output impedance is low - so use a 180R series resistor at the input to the filter (rather than the 195R shown). Remember it has 6dB attenuation in the passband.
The pic's pretty but doesn't give any indication as to what the driving components are, so I suggest suck it and see.
To improve on the jitter sensitivity but still using simple logic, you could try a transversal 1bit DAC.
To improve on the jitter sensitivity but still using simple logic, you could try a transversal 1bit DAC.
Without DAC then you'd be using the Amanero board's outputs directly. Feed them into two of the LC filters I've shown, using 180R as the first resistor.
You could use one of these:
An externally hosted image should be here but it was not working when we last tested it.
🙂