More audio inputs?


Hello! I’m looking into using a Mod Duo (X) for a keyboard setup I’m putting together.

Would it be possible to add more audio inputs to the system? Either by using an external USB audio interface or otherwise?



The mod is based on the Jack system which normally does not allow the use of several audio interfaces simultaneously.

Now, if you are happy with NOT using the super good analog circuitry of the Mod, I have a strong feeling that you should be able to drop it completely and to switch Jack to use your USB interface instead (if it’s got enough inputs/outputs).

For that, you will need to log into the Mod and change the jack configuration.


Ah thanks that sounds interesting! Recently I made a setup with a Raspberry Pi, and was able to add two extra USB audio interfaces to the existing one by using the zita-ajbridge applications:

But also apart from the zita possibility, this is great news. It might mean I can use a Mod to replace a mixer and a couple of effect boxes.


If anyone could confirm that adding a class-compliant USB audio interface (like the ESI Maya44 for instance) by using zita-a2j & zita-j2a will work on the Mod DUO (X)… and that these extra inputs & outputs are usable in the system at low latency… that would be a reason for me to pre-order a DUO X. Thanks in advance.


I am not sure the kernel normally installed on the Duo includes the USB audio drivers. But I suppose you should be able to build them yourself using the cross-compiler.

Can anyone from the Mod team confirm ?

Alternatively, if you have another computer/PC on the side able to run netjack2 and to handle your USB interface, you can make this work with the MOD. The option is available in the MOD.

See that thread : Netjack pluggin


Thanks for the suggestion, but in my particular use case at hand the idea is to have the DUO X take over the function of a small mixer; space is very limited. Also, I think netjack2 would have to run over wi-fi, which is far from ideal for that, and would add considerable latency - which I think it would also if ethernet was a possibility.


the netjack2 solution uses the USB connection between the MOD and the PC.

The induced latency is very small.


Hi together,
to change soundcard settings one has to SSH into the MOD Duo and is responsible for any changes themselves.

Today the zita-a2jbridge (for adding a ALSA soundcard as a Jack node) is not compiled for and available on the Duo. But zita-j2n and zita-n2j (for adding a computer on the network as a Jack node) are available. Please study their man pages. @crosswick I confirm a class compliant USB soundcard will not work in tandem with the internal soundcard of the Duo running release 1.6.

Replacing the internal soundcard with an external USB device works on a early experimental level. At least drivers are compiled into the kernel.

Using network connections does not add to the latency itself. But you might be forced to double the buffersize to avoid XRUNs. I expect WiFi to be very unpredictable unreliable, for example because of the Hidden Node Problem. I you experiment with audio over network, be sure to try what happens on packet loss, reconnection join or if any Jack application starts to freewheel (for example Ardour exporting faster than realtime).

Best regards


Wifi ?


@Azza Could you please ask more specific? I don’t know the answer to "“WiFi”.


Sorry, I was on my phone and could not type much.

In your previous post, you are saying “I expect WiFi to be very unpredictable unreliable”. Sorry to ask, but how is wifi involved in the process here ?


I see. Thanks for explaining.
I have not had time to look, if the driver for a USB-WiFi-Adapter is actually build into the kernel of the Duo; probably not.
Thinking about routing over standard network connections, it is possible to route UDP packets (containing audio) from the Duo over the USB connection to your computer, then bridge it to a WiFi adapter and from there it could possibly go anywhere on the internet. My point is, if you have a dedicated LAN under your control, I expect to transfer audio with almost no XRUNs. Once a WiFi link is included in the network, there are no guaranties it might work.
Short: Technically you could involve WiFi…but don’t do it.
Please feel free to ask again, if I did not answer your question.


Ok, I think we are mixing two different discussions here.

My interest in using Wifi (stated in a different thread) is simply to be able to use the mod GUI from any device on the LAN.

Now, this particular thread is about adding mode inputs to the Duo, and my comment above was that the user could use the particular audio interface of their PC (for instance, my workstation has got 8 input and 8 outputs), and use netjack (through the usual USB cable link, nothing to do with WIFI) to route the signal from their PC interface into the MOD for processing only and then back out to the PC for output via the PC soundcard.

Alternatively, the user could take the MOD out of the equation by just running the MOD software on their PC, for instance, by using the nice KXStudio linux distribution, the mod-host and mod-ui packages (don’t forget to set the MOD_APP and the MOD_LIVE_ISO environment variable before launching mod_host and mod_ui executables).


thank you