low pass filter for DSD

[merlin el mago]

What characteristic impedance for the filter?

 

[merlin el mago]

Butterworth or Chebyshev would be fine - I suggest Butterworth as its simpler to design. The corner frequency depends on you - perhaps 50kHz -3dB would be fine as a first attempt.

A 4th order LC would have two series inductors and two shunt capacitors, followed by a resistive termination

<edit> Attached a schematic based on a design I did for an ESS DAC. Its Butterworth but 30kHz -3dB.

Your schematic can work DSD without DAC?

 

[abraxalito]

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.

 

[merlin el mago]

And if I don't use DAC what characteristic impedance have I to use?

 

[abraxalito]

Cannot understand your question, sorry.

 

[merlin el mago]

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

 

[abraxalito]

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.

 

[merlin el mago]

Could you see in the schematic? http://www.amanero.com/USB_B.pdf

 

[Julf]

I want to filter and amplify the DSD signal directly from the Amanero USB-I2S device.

LampizatOr DSD DAC

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:

No one can help me

By the way, if you go ahead, remember the advice from Lampizator:

We also need a high quality USB cable that is “dsd-ready”. (we sell such cable in our shop).

 

[merlin el mago]

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:

Julf I don't like your post

 

[Julf]

Julf I don't like your post

I am sorry, but you choose to ignore my slightly more diplomatic earlier comment:

I am all for experimenting, but I have to ask what it is that you are hoping to accomplish? You are not likely to produce anything that has superior sound quality compared to systems designed by professional designers, and there is a real risk of burning out your tweeter or causing some other damage to your speakers.

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...

 

[abraxalito]

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.

 

[abraxalito]

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.

 

[merlin el mago]

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.

Marked in red, see the attached pic.

 

[merlin el mago]

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.

First I want to try without silicon, could you suggest a 1bit DAC?

 

[abraxalito]

The Amanero board is silicon-based, there's no solution without silicon possible.

 

[merlin el mago]

The Amanero board is silicon-based, there's no solution without silicon possible.

Sorry I wanted to say without DAC.

 

[abraxalito]

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.

 

[Julf]

The Amanero board is silicon-based, there's no solution without silicon possible.

You could use one of these:

An externally hosted image should be here but it was not working when we last tested it.

 

[abraxalito]

That's valve-based 'Flash' memory?