USB audio interfaces compatible with Duo X SPDIF out

Hi Guys,

I’m looking at taking the audio from the MDX into a USB audio interface for further processing (using an iPad actually). I’ve cottoned onto the idea of using SPDIF to preserve quality. After a lot of research, I’m considering the following interfaces:

  • Focusrite Scarlett 8i6 Gen 3
  • Native Instruments Komplete Audio 6 MK2
  • PreSonus Studio 68c
  • Motu UltraLiteMk5
  • Motu 4pre
  • Motu Audio Express

Some questions:

  1. I presume the MDX outputs SPDIF data at 24/48kHz. Is this correct?

  2. Do I have to find an interface that samples at this rate, or will one that works faster eg 96kHz be backwards compatible and sample at a lower rate? Would doing so put the whole unit into a slower rate?

  3. Does anyone have experience using the above interfaces, or would you recommend another one? Remember I’m using an iPad.

  4. Is is even worth bothering with SPDIF? Should I just use the standard audio outputs with a decent interface at eg 24/192kHz?

Any info would help me greatly!

Thanks in advance!


I ended up ordering a Zoom U-44 as I found one cheap.

They only sample at 96kHz max, which is low for these days, but fine for dropping back to 48k for the MDX.

I’ll post here once it arrives and I’ve had a play around with it.



For SPDIF to work (if I know it right) you need to have both devices with the same settings.

My advice is to be sure that it really works on the iPadOS. It may not be so linear as it is with a computer (especially with not USB-powered interfaces).

It really depends on you. If you want to “gain” some inputs on the soundcard it’s totally worth it.

Cool! I’m really curious to see your setup :slight_smile:

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As long as you have the USB camera adaptor for the iPad, any interface that supports USB audio out or power will work on the iPad.

I use a Steinberg UR-22 MKII for my interface and it’s USB power as well as audio. Didn’t think it was going to work, but it does indeed.

I use AUM to record, but there are other DAWS available like cubasis, FL Studio, etc…

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Yep, I’ve got the camera adapter, USB hub, etc. I’ve got a fair few apps and have recorded on both iPad and iPhone. I was also quite amazed when it worked - and MIDI also!

What’s completely new to me is using SPDIF. Theoretically, I should get the digital signal out of the MDX (so skipping the D->A) and into the Zoom U-44 (skipping the A->D) where it’s then sent as USB Audio into the iPad.

I could avoid the Zoom altogether if the MDX could be plugged straight into the iPad.- but from my experience so far, USB Audio support currently isn’t very stable on the MDX. This is a shame - it would be a killer feature.


If you’re willing to wait, audio over USB is on the roadmap for the MDX last I recall. But seeing as you’ve already ordered your new tascam, you’ll benefit more from it in my opinion lol


I tried with an iPhone and a Presonus soundcard and I was not successful. It was a while ago and maybe the problem was with my adapter (I discovered…not sure if after…that an adapter that I have is a bit dodgy).

There are plans for this. Yet it’s not in the priority for now.

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That’s strange.

I’ve recorded straight to my iphone from my interface for a few tracks, but was not optimal haha

Iphone was even supplying the power through USB. I was using the camera adaptor kit for the iphone. It’s the only way to keep everything powered at the same time

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I need to try it again indeed.

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The iPhone/iPad can only supply so much current to external devices; the camera adapter kit simply allows charging while doing so. To power devices beyond that, you need to use a powered USB hub.

My iPhone 8 can power my Scarlett 2x2 but my iPad Air 2 can’t.

My Zoom U44 just arrived! Will update tonight regarding the SPDIF connection to MDX…


The Presonus soundcard that I mentioned is not powered via USB - it uses an external power supply. So I would say that this was not the problem…

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So the good news is that the SPDIF connection between the MDX and the U44 works fine in “passthrough” mode, where audio from the digital inputs is sent out through the analogue outputs.

The better news is that things also work in “USB” mode with my MacBook. Audio goes from my guitar, into the MDX, out the SPDIF, into the U44, over USB into the Mac, sent through a reverb in my DAW, back over USB to the U44, and out through the analogue outputs. To get this to work, I had to set the interface to 24-bit 48kHz in the settings on the Mac.

The even better news is that it also works in AUM on the iPad or iPhone - again, as long as the U-44 sample rate is set to 48kHz.

I’d call this a big success! :smile:


Awesome news @zappso :slight_smile: I’m happy that it worked.

Hmm actually here could also be probably my problem. I think I was trying with Garage Band, Sample Tank and BIAS FX. Maybe they are not compatible.

It’s very important that you set the sample rate. AUM allows you to do this, not sure about the other DAWs. Until I set the sample rate, the sync light on the U-44 was flashing to indicate the digital signal from the MDX was present but it couldn’t lock on.


Hi, I wanted to understand if this cable is correct to mirror the two channels of the MOD DUO X towards a Motu Ultralite mk3.

thanks in advance for any reply.

Plug-wise, yes.

(Theoretically, SPDIF requires a 75 Ohm cable, but for audio applications the mismatch is not a problem).

If you could report back your results, that would be appreciated.


I just ordered the DUO X, I will do a test and post the results here:)