[alsa-devel] Balanced output support for Xonar: Patches for Virtuoso driver to add mixer option for balanced mono output (PCM179x dacs)

[Christian Wisner-Carlson]

I have the  H6 working somewhat. I added a lot of I2C resets (and a
loop to make sure the bus is free before trying to write to it).
HOWEVER, when the H6 is connected, and i switch from 128x OS, the
sound stops and becomes a high pitched whine or other noise, or just
stops, as if the DACs lost lock on the MCLK signal. The same thing
happens when i play ANYTHING at 96khz or 192khz sampling rate.
However, 88.2khz still plays at 64x OS. Given that a 24.576MHz
single-ended signalis being sent UNBUFFERED over an UNSHIELDED  ribbon
cable, this does not surprise me. I am guessing that the Asus drivers
probably use a lower MCLK rate. Any ideas? My old Audigy 2 buffered
the MCLK (24.576Mhz) with a 74F125, although I am reluctant to do
this. Perhaps I will try replacing the relevent part of the ribbon
cable with a shielded cable. Is this worth trying?

Christian Wisner-Carlson

On Mon, Nov 1, 2010 at 11:59 AM, Clemens Ladisch <clemens at ladisch.de> wrote:
> Christian Wisner-Carlson wrote:
>> I tested this thoroughly with an Asus Xonar Essence ST, although it
>> should also work with the HDAV, Essence STX, and probably other cards.
>
> D2/D2X, Xense.
>
>> The patches that I am posting only give one control regardless of
>> whether or not more than one DAC is connected. I have another patchset
>> that gives individual control of all 4 dacs in the Xonar Essence ST+H6
>> and HDAV+H6 setups (H6 is an optional daughterboard for surround sound).
>
> BTW: any new information about the H6 problem?
>
>> It allows for 4 balanced outputs, 8 unbalanced outputs, or any
>> combination of balanced and unbalanced outputs. HOWEVER, it adds 4
>> mixer controls and the code isn't very pretty.
>
> The controller can route any stereo pair to each DAC, so it would be a
> good idea to have one global control that also affects this routing so
> that, e.g., configuring the card for 4 outputs works correctly when
> playing 4-channel data.
>
> Alternatively, having low-level controls for each detail of the hardware
> is workable when somebody (i.e., you :-) writes a special graphical tool
> to configure the Xonar outputs (any the other settings).
>
> The Xense has one PCM1796 for the front channels and a CS4362A for the
> other channels.  Like the stereo-only cards, this would result in an odd
> number of channels in balanced mode, which is somewhat counterintuitive
> because the controller would need to be fed an extra unused channel.
>
>> Please tell me if this is not the correct way to post a patch, and
>> tell me if it seems like a candidate to be merged.
>
> Your mailer wrapped lines; see Documentation/email-clients.txt.
> Also see Documentation/SubmittingPatches.
>
> Overall, this patch looks good.  But I wouldn't want to apply it without
> the followup patch that handles the D2's four DACs.
>
>> @@ -532,6 +534,13 @@
>>               reg = PCM1796_OS_64;
>>       else
>>               reg = PCM1796_OS_32;
>> +
>> +     if (data->monomode)
>> +             reg = reg | PCM1796_MONO;
>> +
>> +     if (data->rightmono)
>> +             reg = reg | PCM1796_CHSL_RIGHT;
>> +
>>       for (i = 0; i < data->dacs; ++i)
>>               pcm1796_write_cached(chip, i, 20, reg);
>>  }
>
> This function's purpose is no longer to _only_ update the oversampling
> setting; please rename it to, e.g., update_reg20.
>
>
> Regards,
> Clemens
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