No audio when plugging Guitar 2 USB cable

[patastrami]

First of all, hi to everybody and this is my first post here. I just discovered the forum and it seems there are many interesting topics I'd like to dig in!

I open this topic because I have an issue when I plug a jack 1/4" to USB (guitar to USB) cable to my laptop, as I stop listening any audio.

My goal is to set up an audio studio on standard Ubuntu (not Ubuntu Studio), having already installed and configured jackd2, QjackCtl, Carla, Hydrogen, Guitarix and Ardour.

I have been successful in synchronizing Hydrogen and Ardour and record the drums. I am able to hear the drums through my headphones as they are being recorded and play the record back. I detailed the installation & configuration steps in this post, in case you want to have a look. The next achievement would be to record something played from an instrument (specifically an electroacoustic cello) connected through USB interface, and this is where I am getting issues.

I am using a Dell XPS 13 9305 laptop with Ubuntu 21.10. This laptop only has USB-C ports, so I am plugging a USB-A to USB-C adapter to it, and then a jack 1/4" to USB-A cable (in particular, a Behringer Guitar 2 USB cable) that is connected to the instrument.

When I plug the USB, QjackCtl detects two new interfaces related to USB:

• hw:Device (USB PnP Sound Device)
• hw:Device,0 (USB Audio).

I usually select the second one, hw:Device,0 USB Audio (hw:1,0), but I have selected the first as well and I get the same negative result. To do this I go to QjackCtl, button "Setup" and change the "Interface" in its dropdown list.

Once USB is plugged (even if JACK is not up) I no longer hear any sound through my computer. When JACK is on, I still hear nothing even when there are sounds played from apps using JACK (e.g., Hydrogen, Ardour). System plays JACK sounds normally when USB is not plugged.

It is weird because system is actually receiving the sound, though I do not hear it. For example, I was able to record the instrument with Audacity or Ardour and export a file that I am able to hear once JACK is closed AND USB is unplugged (if USB remains plugged, there is no sound on pulseaudio, even when JACK server is already down).

I am NOT using yet Guitarix during the tests, to remove an additional possible source of issues while troubleshooting. Because of the same reason, I have not yet configured a bridge between JACK and pulseaudio.

All apps are connected to system:audio_out, as seen in Carla, so I should hear them as I did when USB was not connected.

One more clue: I tested the same instrument and cable in another computer with a different OS and USB-A ports. It was a MacBook Pro and DAW GarageBand. And surprisingly, the result was the same: once I plug the Guitar 2 USB cable I stop listening any audio during recording or when playing back, even when I checked when creating the project that I wanted to hear myself while playing.

My questions are:

• Is it possible to hear system audio through the computer speakers/headphones while the USB is plugged? Is it possible that this is not the expected behaviour?
• How can it be that the same cable is causing the same incident in two different OS? Is it possible that the guitar 2 USB cable is not working as expected?
• Do I need to change some configuration?
• Among the two USB interfaces offered in QjackCtl, which one is the one I should use?

Many thanks in advanced and sorry for the long post. I didn't want to leave any clues and solutions that I have already tried.

[digitsun]

I'm speculating but the problem seems to be that USB Cable (note that JACK identifies it like an audio interface) don't have audio outputs, consequently you can't hear anything.

[sunrat]

From https://www.behringer.com/product.html?modelCode=P0BBN

...GUITAR 2 USB works with virtually all popular 32-bit compatible recording software including Avid Pro Tools*, Ableton Live*, Steinberg Cubase*, etc., so you can record tracks directly into your favorite DAW – and mix and master to your heart’s content.

32-bit could be the problem.

[tavasti]

Once USB is plugged (even if JACK is not up) I no longer hear any sound through my computer. When JACK is on, I still hear nothing even when there are sounds played from apps using JACK (e.g., Hydrogen, Ardour). System plays JACK sounds normally when USB is not plugged.

If you have pulseaudio running (most likely you do), pulse audio can take new device as default device. And because that device does not have output, no output

Running 'pavucontrol' will give you GUI for managing pulse audio devices.

[Michael Willis]

Trying to use two different audio devices is fraught with trouble and woe. There are ways to kind of make it work, but you would be better off using a single audio interface that can handle both input and output. This recent thread can help you find one that will work for you: viewtopic.php?f=6&t=21799

[merlyn]

AS digitsun said you don't hear audio because the USB to 1/4" jack interface doesn't have an output.

As Michael said using two interfaces at the same time can cause as many problems as it solves.

But if you want to try it ...

I'm assuming when you can hear audio it comes through the built in sound? You want to choose this as your output. If you go to QjackCtl > Settings and Options Dialogue > Settings > Advanced and choose the built in sound as the output in the dropdown 'output device', while choosing the Behringer in the input dropdown, you should hear sound.

This may or may not give a clear, xrun-free output.

[patastrami]

Many thanks to all the replies so far. I had an unexpected trip and was away for some days so I was unable to reply sooner.

I think this topic is very specific to the Behringer Guitar 2 USB interface cable and its compatibility with Linux.

After writing my post I realized that the manufacturer informs that the USB interface is compatible with Windows and Mac only. I guess its compatibility with Linux is not something to take it for granted.

I will try to test it on Windows (according to some users, it requires the previous installation of ASIO4ALL USB Audio Driver) and Mac to see first if (and how) it works on the OS where it is supposed to be used.

In any case, my cable cost 15 €. A proper audio interface (like the ones proposed on Michael’s linked topic, thanks for posting it) would cost 150-250 €. In my ignorance I thought an electric-to-digital conversion was as simple as using the proper cable, but now I know I have to invest some more.

The solution to this topic is, as you proposed, forget about this USB cable interface and get a proper audio interface.

One more question… I read in other topics about a wiki page that listed Linux-compatible devices but link seems broken. Is it available on any other link?

http://wiki.linuxmusicians.com/doku.php ... are_matrix

I guess I cannot return this cable now package is open, so I will perform the proposed analysis (pavucontrol) and change in configuration (QjackCtl) and see if I can use it for something. In any case, it added to much noise to the sound, so the USB interface is quite useless anyway.

[tavasti]

In any case, my cable cost 15 €. A proper audio interface (like the ones proposed on Michael’s linked topic, thanks for posting it) would cost 150-250 €. In my ignorance I thought an electric-to-digital conversion was as simple as using the proper cable, but now I know I have to invest some more.

For real interface, Behringer UM2 or UMC22 are sufficient if you are looking for basic entry level stuff. And for bit better, consider UMC202HD.

[TygerTung]

You should be able to get an interface quite cheap second hand. Especially as the older ones lose Windows support (M -Audio M Box 2 for example), but still work fine in Linux.