Direct Drive DSD Files Without Any DAC

It is quite some time that one forum on the internet was shocked with someone amplify a raw DSD digital signal without any DAC, and it works!

This issue also takes my curiosity and I want to try how could this possibly done.

I am searching more information and this is quite makes sense since the DSD file is basically a pulse density modulation and it is looks like an analog signal show on the oscilloscope. This is called data stream that very fast data generate and creating just like the analog signal.

It is completely different with common pulse code modulation or PCM in most music files, which they are basically codes that need to translate first before convert to the analog by using a DAC.

So in this post, I will try by myself this digital DSD files amplify directly to analog.

First things first, I need the DSD capable receiver.

I am using the XMOS U208 USB receiver with Altera Maxx 2 combo to translate the DSD signal.

This USB receiver works perfectly when connecting to PC or Android using UAPP. In this case, I am using Android with UAPP installed on it which works very well for any kind DSD files.

I don't have the DSD music files. The one source I know is free and available to download is from 2l websites. They shared the DSD files up to 11.2896 Mbps and one song for more than 400 MB.

Once all equipment ready, then I only need a DC regulator to make 3.3 volt DC out to feed to this USB receiver module. This DC voltage is required for the connection between USB receiver to the Android. While connecting them to the Windows PC doesn't need any voltage present to the USB module.

Then I also need to make a low-pass filter to remove unwanted high frequency from the raw digital DSD. Quite strange that this LPF circuit is mostly for the analog signal, but in this case I am using it for this DSD digital files.

The components for each channel is 1st order LPF using R-C components, a 2k2 ohm resistor, then a 1nF capacitor to the ground. The DC blocking capacitor is needed after this LPF and I am using 4,7uF electrolytic capacitor.

Lastly, one resistor after the capacitor is put to the ground to determined the impedance output. I am using 100k ohm for each channel.

That's it! It is only a LPF circuit without any DAC at all.

This LPF module then connecting to the digital out from the USB receiver.

LRCK is for left channel DSD

DATA is for right channel DSD

GND is for audio ground

There is a DSD signal lock pin on the USB module. This signal goes high when the module processing the DSD files from the host. I  put a 100 ohm resistor in series with LED to the ground. This LED will lit once the DSD files is present in the module.

I connect to the amplifier and start to play the DSD music files from the UAPP.

and.....

It play music very well.

Yes, this DSD digital files play the music without any DAC.

The sound is surprisingly acceptable.

I think it will be so much high frequency noise and digital aliasing in the music, but it is not. The sound quality is warm, quite detail and balance on every audio frequency.

I listen carefully the sound quality and it is quite musical. It is really good to hear the DSD digital audio directly.

But it is not without any flaw.

The clicking noise every track changes is always present.

There is hiss noise on the background that cannot be avoidable.

And you don't want accidentally change to the PCM music files.

I just warn you to always lower the volume knob every time you want to change the music files to avoid accidentally choose the PCM music files with their static noise that unbearable to hear.

After all, this experimental project is worth to try. At least I have this experience to proof that it is true for the DSD files can be hear directly from its digital files without any DAC.

And the sound is surprisingly good enough to hear.

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