New reworked driver for Wolfson/Cirrus Logic audio card

Hias,

A huge thank-you for all the work you've put into supporting the Cirrus Audio card.  Until now I've been using your kernel packages, and have just got round to trying the latest official 4.9 kernel which is also working very nicely.  It's a real shame that the Cirrus card has (or appears to have) gone out of production just when the software support became so good.  The older Wolfson cards are still available, so perhaps I'll get a couple and try modifying them to fit a 40-pin header.  Anyway, thanks again for everything you've done.  I really do appreciate it.

Tim

The Cirrus Card does seem to be out of stock everywhere - what a shame.  I just started working on an alternative ultrasound sensistive microphone, since the electret type I was using has been out of production for years and is now virtually impossible to get hold of.

What other options are there for recording audio at 192kHz with the Raspberry Pi?

Hi John,

I have done no calculations on my speakers, and also do not know where to get the data to do them.

The column speakers do have quite some volume ( in liters ) but the low drivers are not as big as a separate ( active ) subwoofer would have.

For the about 16 CM drivers I just guessed 400 Hz as a first attempt.

And with very steep filtering handover is more pronounced and thus easy to noticed if not set correct.

I understand your setup where you use line out and headset out to carry the same stereo signal, but filter them differently, and in combination with your external subwoofer speaker filter and mono , add combine this into 1 low signal that is amplified in that box.

My idea was to use the 2 channels  in 1 card to both carry , f.i. the left channel.

And then filter 1 to pass high, feed it to the on-board amplifier and feed the mid/high section of my speaker.

And let the other to pass low , feed it to the on-board amplifier 2 and feed the low section of my speaker.

This woud reduce my output to just the left channel, but with a separate amp for low and mid/high.

If I remember correctly from playing with the alsa options the filters for left and right are separate, and routing of 1 signal channel in both output channels is possible.

The experiment would be to see if one could obtain more effective output by filtering before amplification , and secondly if it would produce a noticeable result.

.....

Thinking of it a bit more now, using a second pi and card to drive the other channel would generate time differences in left/right channel reproduction and create distortion in the stereo image. And this is likely to be much more a disadvantage than the gain one could obtain from a bit more power.

So if I would choose Mono output, the idea might be useful, but for stereo external amps are required to get a bit more output power.

Regards, Marcel

Those on  chip D class amplifiers are remarkable for what they do, but personally I would not use them.  You could arrange to use that amplifier for just the high frequency components where less power is needed (above 1kHz). That would still lead to you needing a stereo amp for the LF though.  I am fairly sure that some Lenevo tablets use the 5102 power amp to drive their speakers, so that gives an idea of where they do well.

I am not sure whether you picked up on my observation that both the line out and headphone out are capable of driving 15 ohm loads (though I repeat I would not do it).  So conceptually you could have Left channel feeding two filters (one high pass, one low pass) and these two signals feeding the headphones out.  The Right channel could follow the same logic except it could feed the line out socket.

However I presume you are using speaker out to drive your speaker, which is capable of driving 3 ohm loads. And there you have just two channels ...

  There are so rediculously cheap small class d amps out there eg

PAM8403 Ultra Miniature Digital Power Amplifier Board Class D 2channels x 3W 8′′ | eBay

at 0,30 euros.

I would use a couple of those and protect my precious Wolfson!

As to connecting two Wolfsons/Pi together, I wouldnt.  unifying the two I2S clocks represents a huge effort

Thanks John,

Indeed I did not notice enough the line out  AND  headphones out both can carry the same signals with their own individual filters.

Combined with external amps one could indeed build a setup for bi-amped speakers.

I definitely want to experiment with that in combination with a multi channel amp I already own, it would just need 4 analogue  inputs to be active to 4 amp outputs.

If combined with speakers out one could do a how-mid-high separation but that is fun in theory only I presume.

On the D-amps indeed they do perform much better than people do credit them for.

My experiments with the PAM 8403 boards are positive, but I prefer the on-board amp in the cirrus logic audio card.

I really do recommend you test them once. Depending on the the effectiveness of your speakers it does create enough signal to enjoy your music.

Combined with the digital silence of the card , it is ideal for a bed side audioset to wake you up in the morning , without the sound of the sea during the night.

In need to do more reading on the amp used in the card....

Edit :.As the 5102 you mentioned is rated at 2*20 Watt max and should not be fed with less than 8 volts.....

Edit : confused the wolfson 5102 chip with an other popular chipmakers 5102.

Edit :  2 watt D-amps according to chip datasheet

Regards Marcel.

Hi John 

I hope that this finds you well!! I see the revised PCB could you send me the file for PCB fab  requirements like dimension length X Width (mm), Layers, thickness,

you have any picture to take a look the PCB assembly

Thanks in advance  

Hi,

Here is the KiCAD file that I used.  You may want to add to it,  feel free!  And if you are going to get some made with gold plated pads for the pogo connector, please let me know  ..... I would like to buy a couple if possible

Regards

John

Hi,

Here is the KiCAD file that I used.  You may want to add to it,  feel free!  And if you are going to get some made with gold plated pads for the pogo connector, please let me know  ..... I would like to buy a couple if possible

Regards

John

Postscript:-  I cannot post the file directly, forum rules.  If you pass a private message with an email address, I will send it straight to you

Hi John   I can't  send you a  private message ...we must be  connected first 

Best Regards 

John , follow also me 

Hello Athanasios (and others)

Producing printed circuit boards is certainly possible (and I have spoken to the fabricators), but I will need to add to the design I published some time ago.  I am putting this message out to the community in order to see what I should add to the design.  Hias has already suggested that the board should be larger so that it can support the wolfson.  But are there other useful things I should try and incorporate? I guarantee nothing, but suggestions are welcome!

Hi John

At first, I would like to thank you for your help

Your prototype board meets Hias, hardware modifications, I have tested it also and works perfectly. 

So why not to move forward with some printed circuit boards for test

Remain the problem with the CAD layout to generate the Gerber

All the best

Hi John

At first, I would like to thank you for your help

Your prototype board meets Hias, hardware modifications, I have tested it also and works perfectly. 

So why not to move forward with some printed circuit boards for test

Remain the problem with the CAD layout to generate the Gerber

All the best