LinuxMusicians

Dear all,

I recently acquired an audio interface: U-Phoria UMC202. I never connected an electrical instrument to Linux before, but soon enough I was able to record the input with simple programmes. Problem is: I am so far unable to listen the input through the headphones (or speakers). I expect it to be easy, essentially feeding an audio input to an audio output, but DuckDuckGo is now exhausted without much coming. Alsamixer looks the more promising, but the interface in the version I have does not match the few guides online. Any suggestions welcome.

I work on Ubuntu 20.04, if that is relevant.

Thank you.

There is a direct monitor button on that device. If you engage that then you will hear your instrument input in the headphone jack.

If the instrument is electric guitar make sure to engage the "INST" button on the gain section to switch the input to a high impedance or Hi-Z input.

The most common setup is to use the jack audio system and software such as qjackctrl, patchage, carla with it's patch bay etc. to route the audio inputs through different types of software for processing, recording etc. and then route the outputs of these software back to the audio playback ports.

system
capture_1 ---------------------> Software IN system
Software OUT L --------------------------> playback_1
Software OUT R -------------------------> playback_2

The processed sound is now available at your output jacks on the 202 device and can be plugged into powered monitors, mixer/amp etc. Also with the direct monitor button disengaged the processed sound is available at your head phone jack.

Thank you bluzee for chiming in. I do not wish to route the input back to the audio interface, at this moment I do not have cables for that.

qtjackctl shows 2 different inputs, but none is the audio interface. One is the internal microphone of the laptop and the other is the microphone embedded in the headphones. After reading your message, it looks like I am missing some step prior to start up the jack server, but am not sure what.

Cheers.

Yes, the setup part of qjackctl. After you plug the interface into USB start qjackctl and select the setup button. There select the USB interface from the interfaces drop down menu and click OK. Now click start and jack will run on your USB interface instead of the default built in sound device. If your system uses Pulse audio normally as most do you can use PulseAudio Volume Control and on it's configuration tab set the USB device configuration to OFF. In this way the two won't interfere with each other.

Physical cables are only required if you wish to take the sound from your 1/4" output jacks on the audio device to a mixer or amplifier. You can listen through head phones plugged into the audio device in their absence. The connections made in qjackctl are inter-software connections. They let you decide which software receives audio from your physical input on the device and ultimately which software sends audio back to the physical device's phone jack and out put plugs. Remember also now that your recording software or other software may need to have their preferences changed from using pulse or alsa as input/output to using jack for input output before their connections appear in qjackctl connections. For testing you can simply connect a capture port to a playback port in qjackctl connections..

There are a great many setup guides and suggestions on the web and this forum for jack audio.

Hi again bluzee,

I am able to follow the steps you outline, but still no sound is transported to the headphones. The two inputs from the audio interface are present in the connections menu, they are connected to the playback channels but no sound is audible.

I do not have headphones with a 1/4" jack, so I need some sort of cable adapter to use the direct monitor function.

Thank you for bothering in any case.

Ummm.... OK. I'm thinking that you are plugging headphones into the 1/8" inch jack on the computer built in sound card? The sound doesn't happen on both sound devices unless they are linked together in jack which is complicated. The 1/4" headphone plug on the Behringer is where you need to plug in to. For 1/8" plug headphones there is a simple adapter plug to bring that up to 1/4" Should cost less than a dollar.

Hello again, a quick update on this.

As far as I can tell jack does nothing. It routs sounds neither way, either from the audio to interface to the internal sound board or the opposite. And since most of the guides out there advise one to connect the audio output to the interface itself I decided to abandon jack altogether.

Eventually I got hold of a 1/4" adapter and have been using the interface that way. But well, that does not really allow to play along some tracks from the computer, or even a rhythm box, since all the audio interface is able to reproduce are the instruments connected to it. I am now wondering if I just bought the wrong hardware.

Thank you for bothering.

The device you bought is fine.

I struggled a bit with my first interface too. I wrote a little tutorial with pictures and sceeenshots which might be helpful to you: https://sanderson.band/2017/09/04/focus ... me-studio/

It is for a different interface, and is a little dated, but the principles should be the same.

You are right that you can probably get by without jack, but I found jack to be helpful to learn the concepts and get the device setup figured out.

Hi milo, thank you for your reply. I read your blog, it is very similar to what bluzee wrote above. Selecting the audio interface as input and output device in Jack has no effect whatsoever. The system sound continues to come out of the internal speakers, or from the headphone jack, but never from the audio interface. Likewise, no input from the audio interface is routed to the system.

blauzee thinks that the audio interface is working correctly. It could be that I just got the wrong piece of hardware to route both the instruments and the system sound to a single output.

Cheers.

It's just a little hard to get your mind around at first. The two audio devices are completely separate and they are not physically linked in any way. You can't send any data between the two unless a link is created. This link can be created with physical patch cords or it can be done with software. There are issues with either way and both will require some research to learn how to accomplish.

Teaching yourself to setup and use jack on one device at a time is a good place to start. Jack can let you route the audio from your input through a multitude of processing and amp simulation options and then back out to the head phone or monitor output jacks. It can simultaneously allow you to playback pre-recorded sound tracks and mix together with the live sounds of your guitar. Applications like carla or patchage can create visual representations of these connections to simplify the process. It opens up endless possibilities.