[LAU] Neophyte questions re: selecting an audio interface

[Clemens Ladisch]

Chris Metzler wrote:
> Yeah, this was one of the questions I meant to ask, and forgot --
> whether there are PCIe options.

AFAIK the only PCIe sound chips are made by Creative (consumer
cards, no good Linux support).  It is possible to put a PCIe/PCI
bridge chip on a card, but the only vendors that do are ESI and
Asus.  ESI uses Tenor chips, which aren't supported at all; Asus
Xonar cards are useful only if you do not need more than one stereo
consumer-level line input (but then they have very good ADCs; see
<http://www.alsa-project.org/~clemens/xonar-models.html>).

> Clemens Ladisch <clemens at ladisch.de> wrote:
>> Chris Metzler wrote:
>>> - Latency tuning possibly required (identifying IRQs associated with
>>>   PCI slots and picking slot accordingly)
>>
>> USB and 1234 controllers are PCI devices too, so you have exactly the
>> same IRQ problems, except that you cannot change the slot of an
>> onboard device.
>
> Good point.  But they don't typically share those IRQs, do they?  Or if
> they do, isn't it with a PCI slot, so that you might benefit by moving
> anything in that slot?

Maybe.  Usually, there are just too many onboard devices.

>> USB has lots of overhead.  It can just barely fit eight 16/48 channels
>> into USB 1.1; full-duplex 24/96 is not possible.
>
> Just to make sure I understand what you're saying here:  24/96 means
> 2.3Mbps, so full duplex would mean 4.6Mbps, which is less than the
> USB1.1 12Mbps hard limit.  But there's so much overhead in USB traffic
> that you don't really ever come close to having 12Mbps available in
> USB1.1, and in fact wouldn't have 4.6MBps available for one channel
> 24/96 full duplex?

No, two channels.  The limits are 512000 bytes/s per direction full
duplex or 1023000 bytes/s half duplex.

Mono would be possible, but I don't know of any such device.


Regards,
Clemens