microphones and the cirrus audio card

There is definitely a microphone bias circuit in the schematics, and even a script to enable recording from a biased microphone.  But I tried just now and couldn't actually measure any bias voltage.on the line-in connector.

Ok Great - thanks Tim

so maybe it has to be enabled?

bw

grant

Grant, if you take a look at the "scenario" scripts supplied in the Cirrus Logic disk image you'll see that Record_from_lineIn_Micbias.sh includes a line to "Enable MICBIAS".  Though for me it doesn't seem to work.

Thanks, Tim

I'll download and have a look.

I was waiting to buy the card until finding out if this functionality exists - it sounds from this as though it does and presumably just needs some tweaking. It sounds like the hardware setup visibly supports PiP via the Line In. So I'll get a card and test.

If anybody is still working with audio streaming with the Wolfson, we have a disk image available from  here, currently being used for a nice live audio stream from Seoul here. This image was very much dependent on support from Ragnar Jensen.

I can't say I particularly look forward to trying to make a new image with Darkice and the Cirrus drivers.. well but with this new capability it should be well worth it

bw

grant

Great thread, all information is very useful.

Some additional points

• The Cirrus card has been updated to include stereo MICBIAS on the Line Input.
• The script setup file in the image will configure the ability for microphone recording
• After executing the setup script, the MICBIAS voltage will only be enabled when an active record is configured, i.e. arecord. This is part of the software power management.
• The MICBIAS voltage is typically 2.7V.

Thanks, Scott

That's very useful and clarifies the query about enabling the bias voltage.

2.7V is not as high as we'd like for the electret microphones we're using, but we will see how it goes.

I ordered a couple of soundcards yesterday and we'll run some tests and post updates, and no doubt questions, here

bw

grant

Thanks, Scott

That's very useful and clarifies the query about enabling the bias voltage.

2.7V is not as high as we'd like for the electret microphones we're using, but we will see how it goes.

I ordered a couple of soundcards yesterday and we'll run some tests and post updates, and no doubt questions, here

bw

grant

Electret condenser microphones via the Cirrus Logic Line In - updated

Hi Scott and all

We successfully installed Darkice over the new Cirrus image and all works well. Much easier than previously with the Wolfson.

We ran the use script to record from the Line in with Mic Bias as suggested above, and plugged in a pair of omni stereo microphones of decent quality.

We are now streaming what appears to be very good, detailed audio with a good tone and nice spatial sense - very promising.

However, we have a loud hum which sounds like an earthing type issue.

It looks like there is a hi-pass filter in the script:

# Configure the input path for 0dB Gain,  HPF with a low cut off for DC removal

amixer $1 -Dhw:sndrpiwsp cset name='LHPF1 Mode' High-pass

amixer $1 -Dhw:sndrpiwsp cset name='LHPF2 Mode' High-pass

But the loud hum remains and filtering it would severely impact on the audio.

Any thoughts on how to address this would be great

Thanks

Best wishes

Grant

Hi all

Further to my post on hum using ECM microphones with the Cirrus Line In, we've found that the hum is not present on all microphones.

So this probably  shouldn't  be considered a serious problem.

We'll test the Primo EM-172 and report on how those work.

bw

grant

I would be very happy if you could let me know how you managed to do this.

I've purchased the card, and for the life of me can't get it to work with Darkice/Icecast2.

Wanted to use Darkice and Icecast2 for streaming live binaural audio to a on-line radio web server (working on my other Raspberry Pi and Behringer UCA202)

Just that the Behringer is a tad noisy, hoping the Cirrus card is much less noise floor.

Wanting to stream MP3 live audio from the cirrus card through to a 3G mobile network here in the UK.

Regards

Hi Alan

We found it's a little tricky compiling Darkice over the Cirrus Logic image. We will make a disk image available over the next couple of days and let you know

bw

grant

Thanks for letting me know that you are on the case Grant.

Looking forward in hearing from you.

Regards

Alan

Hi Alan and all

We have a disk image that streams stereo audio using Darkice and the Cirrus Logic Card with Pi B+ or A+. It uses the Line In with bias voltage by dafault, and has been working well with electret condenser microphones.

It is available to download with notes from the soundCamp resources page here (where there are also images for the Wolfson and other setups)

Best wishes

Grant (soundCamp)

Great stuff Grant, one problem!

I need another 734PB of disk space to extract.. tried downloading twice, must be corrupt, same result.

Will try later this evening.

Regards

Alan

Hi Alan

Thanks for picking that up.

I'll check it out and see what's going on

bw

grant

Hi Alan and all

We have uploaded a verified new disk image to  the soundCamp resources page

soundCamp resources - Pi SD Card - Download

I hope that will work fine now

Let me know if you have any other issues

bw

grant

Hi Grant,

Thank you for your hard work, and to the others who are working on this cirrus logic audio card too.

I've tried the new image, it works, I've managed to stream on the test stream, there's a little interference coming through a "buzzz" which changes as you move the card and wires about, you can get it so that it is almost gone too.

Not sure if it has to get to the GUI? Would have liked headless, I've tried turning off the GUI but it's got some script running for the IP which stalls the command line. Changing the host name breaks some things too.

I'm confused as how darkice works without Icecast2.

My new account for the testing microphone site breaks the streaming as well, not sure why, there is a conflict of terms in the conf file to the information given after new account conformations.. being a fair newbie probably isn't helping me comprehend what is going on in that config file.

Was hoping to run SAMBA, WEB Server, noip ddns client, sakis3g, Icecast2 and stream to another online server, though I am quite interested with the microphone radio site, as it works on "switch on", so why not use this without me faffing about trying to get other things to work when not needed? probably the challenge! but an easy excuse not to try.

I hope to have some answers from the help guys on the microphone site, so with luck will have "Liverpool_3D_binaural" sound stream up and running soon.

I am so grateful for those who have worked hard to get things going, thank you very much guys!

Regards

Alan