[linux-audio-user] Audio interface recommendations

JP Mercury swirlee at stickist.com
Fri Jan 14 14:00:29 EST 2005


On Thu, 13 Jan 2005 19:57:41 -0500, Jon B wrote
> Recommendations so far:
> 
> 1. Echo Indigo I/O
> 
> Looks good.  Only thing I'm worried about is the converters being
> inside the computer.  Is it really well-shielded and flat noise 
> floor? I guess if there's some whine but it's *much* lower than a typical
> sound card, I could live with that.  They look pretty inexpensive,
> regardless.  $180 or so.  Maybe I should just get one and try it.

The converters in the Indigo sit just outside the computer. The card plugs in
and the converters/amplifiers/jacks stick out about an inch from the CardBus
slot.  

Here's a picture:
http://www.stereophile.com/images/archivesart/1104indigo.1.jpg

The sound quality I have found to be very quiet, even at high gain- definitely
a cut above any internal PCI sound cards I have heard. 

Here's an article that talks about Indigo's sound quality:
http://www.extremetech.com/article2/0,1558,1325716,00.asp

> > They deliver real-time performance at 96kHz, 24 bit
> > down to 32 samples.
> 
> By "down to 32 samples" are you talking buffer size?  Is this what
> JACK calls "frames/period"?

Yup. Your latency is "frames per period" / sampling rate. 

> So PCMCIA is definitely capable of low latency, comparable to an
> internal sound card?  (Comparable to PCI, I  guess?)

It seems to be less an issue of the bus (PCI vs PCMCIA) and more an issue of
how the hardware is configured-- IRQ assignments, DMA on disks, kernel
tweaking, etc. For me, portable low latency was the deciding factor for going
with the Indigo IO and it has paid off.

> I am looking for something in between these in price range.  $300 or
> so.  The Indigo would probably be ok, but maybe better than that... 
> Is there anything with MIDI, too?  I haven't learned enough about 
> MIDI interfaces to understand the kind of latency involved, or used 
> it very much with ALSA, but something that could handle both at low latencies
> would be great.  (Or two separate things, but I only have one PCMCIA
> slot.)  I have a Midisport 1x1, but it has bad latency in windows, 
> and I haven't bothered to figure out how to get it working in Linux.

Your latencies in MIDI are going to come mostly from the transmission protocol
itself. It uses a slow data rate, so it'll always have millisecond latency. 

Good Luck,
-JP Mercury




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