USB microphone

[janeriksteel]

Hi,

I already got one of these images working with a hifiberry card, but I was wondering if it might be possible to use a USB mic for the input and the built-in headphones for output?
When I check with arecord -l and aplay -l, my record device is card 2 (usb mic) and my heaphones are device 1.
Would it be possible to set separate devices for each capability and potentially get this working with a usb mic.

My main motivation for this is to reduce the price of the box I'm building for jamulus users, and I typically find the FiFine USB mic does the A2D conversion about as fast as an external audio interface.

When I try to start the jamulus, I get errors about the validity of the alsa device. I tried messing with the hw 0,0 settings in the jackrdc.conf file, but I wasn't able to find a combination that worked for me.

Any suggestions?

Thanks,
Jan-Erik

[kdoren]

@janeriksteel I'm afraid I don't have good news for you.

In theory, what you want to do is possible in ALSA. It's done by creating a virtual asymmetric device of type "asym" that captures from one hardware device and plays back to another. Then you would configure jack to use the virtual device.

However, in practice I don't think it will work well if at all. I tried this and found that the RPi headphone out needs a lot of buffering - 512 byte period, and the extra overhead made things unstable (overruns, etc). Even if it's possible to get it working right it would be painful to get there for not much upside.

In the past I have tested the Pyle PDUSBPP10, which is a "USB Mic" without the "Mic", it has an XLR connector that allows you to plug it into the mic of your choice, and it has a playback interface with headphone jack and volume control. It works pretty well but the mic preamp does pick up a little bit of power supply noise from the RPi.

In the end we wound up going with the Behringer UM2, it's cheap, works well, and lets you plug in any mic or instrument you want.

[sharonesl]

This question seems to be similar to one I've been thinking about.

I have a few Jamboxes with HiFi Berry DAC +ACD Pro cards and I'm working on setting the input and output volumes as high as possible using alsamixer settings. As I was looking for more sound, I wondered if it would be possible to add a USB microphone with a Sabrent sound card to pick up an instrument while the HiFi Berry picks up the vocal.

It sounds like a (asym) virtual device set up would be required. (over my head !) But good to know that is what would be needed. I innocently thought maybe patchage would work somehow. Does linking two sound cards also need to be done with a virtual device set up?

By the way, I also tried the Pyle PDUSBPP10 along my journey. Too much noise.

I haven't tried other microphone preamps, but microphone choice seems to be an important factor.

So far, the Behringer UM2 has proved to be the easiest, most reliable, low cost option.

[kdoren]

@sharonesl hifiberry has stereo input, so you could run 2 mics into it (and crank up the mic preamp gain with the amixer command as described in another post here). If you set Jamulus to mono in / stereo on, it will mix them to single channel.

You could also put a cheap analog mic mixer in front of the hifiberry or other input.

In theory you could add a second USB mic input, then create a virtual mixer ALSA device, the an asym device so you could input from the mix device while playing through the device you want. But I wouldn't advise it, it's complex, hard to get working, and likely to cause problems or not work well.

[sharonesl]

Thank you. Running two mics worked. It also worked to run my guitar into one of the stereo mic inputs. I turned the hifi sound card gain way down on the guitar input and got a great sound for recording in Audacity. Jamulus levels looked good too, but I haven't tested the set up in live play yet.