[LAU] Neophyte questions re: selecting an audio interface

Chris Metzler cmetzler at speakeasy.net
Sun Jan 8 01:19:56 UTC 2012


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And thanks for your reply as well!

On Sat, 07 Jan 2012 00:20:38 +0100
Clemens Ladisch <clemens at ladisch.de> wrote:
>Chris Metzler wrote:
>> PCI
>> ---
>> Cons:
>> - Outdated technology -- PCI slots being slowly phased out of modern
>>   motherboards
> 
> In the consumer space, sound cards are switching over to PCI Express.

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


>> - 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?


>> - Computer-caused interference noise possible unless audio
>> converted to digital domain outside computer
> 
> I don't think this is a problem in practice.  I've never heard of
> actual noise problems of PCI audio interfaces; all the reports I did
> hear were from cheap USB devices that picked up noise from the
> computer's power lines.
> 
> (Asus and Creative are in a fight over who can build the sound card
> with the highest SNR value, and achieve 118 dB when recording, but
> these cards are designed for "HiFi enthusiast" consumers.)

I've certainly had some audible noise generated by video activity, but
not a lot and it's rare.  But I wouldn't want it if I was trying to
record the cleanest signal possible.


>> USB
>> ---
>> Cons:
>> - A single 24/96 channel means 2.3Mbps; 12Mbps nondirectional hard
>>   limit under USB 1.1 so only 2 channels full duplex,
> 
> 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?  Do I have you right?

Thanks again!

- -c

- -- 
Chris Metzler			cmetzler at speakeasy.snip-me.net
		(remove "snip-me." to email)

"As a child I understood how to give; I have forgotten this grace since
I have become civilized." - Chief Luther Standing Bear
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