Home > General > PCM (I2S) and DSD on the Same Wires

PCM (I2S) and DSD on the Same Wires

November 22, 2012 Leave a comment Go to comments


DACs using same input pins for handling PCM and DSD are not new but are not very common. If we peruse the web, we find a few of them. Mr. Bunpei has listed a few of them in this post: [981] many months ago.

  • The Sabre32 ESS9018 DAC is of course one of them (through the use of clever wiring)
  • The TI PCM 1795 (page 21 of datasheet [link]) and the AKM 4399 (page 4 of datasheet [link]) are two other DACs that share the same pins for PCM and DSD.

Most DACs however, have separate pins for DSD and PCM. For example two well known DACs, the DSD1794 and WM8741 have separate connections for PCM inputs and DSD inputs.

DACs sharing input pins for DSD and PCM are interesting because of the potential of switching between DSD and PCM without the need of switching input wires, and if used with an interface that can equally transmit both PCM and DSD through the same output pins, then there is no need for using any external switching mechanism that can affect the signal integrity so preciously sought after by audiophiles 🙂


Audio interfaces sharing the same output pins for DSD and PCM seems a new thing. So far, I am only able to identify these devices:

  • Amanero USB interface
  • SDTrans memory player [link]
  • XMOS USB Audio 2.0 Reference Design Board [link]. Firmware here [link], [link]. Other XMOS-based interfaces may also support DSD/PCM with the aforementioned firmware.

These interfaces, together with DACs that share input puts for DSD and PCM  allow the “transparent” and even automatic switching of DSD and PCM without the need for external signal switchers. This is the appealing part for audiophiles. The “less is more” approach; the “direct wire” connection… 🙂

Unfortunately as of this writing, two highly regarded interfaces, the XMOS WAVE IO [link] and the EXAU21 [link] do not support this “mode” of sharing output pins (WAVE IO does not support passing DSD yet, but it is just a matter of firmware). These interfaces would require an external device to switch between PCM and DSD outputs.


Using the same pins to pass PCM an DSD is not enough to enable the passing of the signals and the “transparent” and automatic switching between PCM and DSD. For this to happen, the  pin assignment of the audio interface must be compatible with the pin assignment of the DAC.

Here is a table of all the compatible DACs and interfaces showing how the DSD pins are mapped to the PCM/I2S pins

I2S Pins
ESS9018 [link]
PCM1795 [link]
AKM4399 [link]
Amanero(1) [link]
SDTrans [link]
XMOS Ref [link]
BCLK DSD Clock DSD Clock DSD Clock DSD Clock DSD Clock DSD Clock
DATA DATA Right Data Left Data Left Data Right DATA Right DATA Right


(1) With driver 1.0.56, If using driver 1.0.5 or earlier, then the channels are swapped.

As shown above, there doesn’t seem to be a standard way to map the DSD DATA pins to the I2S LRCK an DATA pins. It seems SDTrans, XMOS Ref and Amanero with the latest driver are matched with the ESS 9018 DAC channel mappings (for good reason).

If you wish to use the interfaces with the other DACs, then the channels need to be reversed. Fortunately, they can be remapped in foobar as shown here [link]

(Update 11/22/12): Amanero has released a new version of the firmware [link] reversing the channel mapping. (Although the driver with the older firmware fixes the problem). However, there are reports of some bugs, so wait until a more stable version or more testing is done before upgrading the firmware. In the meantime if you still have the old firmware, just use the new driver and enjoy experimenting 🙂

  1. Bunpei
    November 23, 2012 at 06:54

    Thank you very much for quoting my post in the past! I have completely forgotten the post and could read it again. Your collective compilation works have always important values.

    • BlgGear
      November 24, 2012 at 04:43

      Hi Bunpei,

      Seems you are always a year ahead of me…

  2. David Quayle
    November 26, 2012 at 08:10

    I’d be very interested to see some photo’s of your system as it is know, the insides of course 🙂
    I had not intended on putting a USB input for my BIII build but I think you have inspired me.

    I have been advised I would need a Sidecar for the switching, what would you recommend for the actual USB interface?

  3. David Quayle
    November 27, 2012 at 02:02

    I was hoping to put the USB interface in the case with everything else & to keep costs down I was thinking of going with the Amanero.

    “I am using the Buffalo II in voltage mode directly connected to a pair of Hypex UCD180HG amp modules through an RC filter to filter potential high-frequency junk…”

    How’s that working out for you? why did you choose that path?

    • BlgGear
      November 27, 2012 at 15:22

      I actually have a legato “in the box” which I have not yet built. Been happy with v-out mode. Good recordings sound superb, bad recordings… -there is nothing you can do about it. Not sure if I am missing anything. According to spec, you give up some SNR (which actually is a system thing). Keeping things simple help me have a reliable system especially as this is as much about listening to music as it is tweaking the signal path. I have an engineering background, hence the technical bias to what I do.
      I’ve “given up” listening for “artifacts” long ago, and I am not much of a “soundstage” guy. Music sounds really good and modding is really fun!

  4. David Quayle
    November 27, 2012 at 21:08

    Thanks for the relies, it’s always good to hear about other peoples experiences.

  5. David Quayle
    November 29, 2012 at 02:36


    You say

    “the Musiland 01US looks like a worthy upgrade to the Musiland 03US and for half the price!” & “Musiland 03 US which is still a favorite due to several innovations including the use of USB bulk transfer”

    Rather than me use the Amenaro in my build would there be any draw backs using the Musiland 01US?

    • BlgGear
      November 29, 2012 at 05:18

      Well, the Musiland can’t play DSD files, and you have to tap the I2S. The Amanero plays DSD files and is ready for I2S out of the box

  6. David Quayle
    November 29, 2012 at 10:02

    Thanks again

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