semi-pro PCI snd crd for linux

[Lennart Sorensen]

On Tue, Sep 04, 2007 at 12:24:43PM -0400, Chris Aitken wrote:
> I'm glad you put it that way. This is what I don't get. The way I 
> understand TRS is that it is stereo in /one/ plug. Tip, Ring, Sleeve 
> represents left and right channels going through one cable. So, your 
> statement, "A single TRS port is one channel" doesn't make sense to me.

So all TRS is is tip ring sleeve connectors.

There are two common (and completely incompatible) uses of the TRS
1/4" jack.  Consumer stuff uses it like they use the 1/8" stereo jack,
which is signal left, ground and signal right.  Since a signal by itself
is pretty susceptible to noise and interference, the pro users have a
different setup.  The balanced audio use of the same 3 connector 1/4"
jack is to have signal, ground and inverse signal.  This means the
signal is transmitted as a differential signal, and any noise picked
up by one signal like is likely to be encountered by the other one as
well which means when you take the difference between the two the noise
mostly cancels out in the equation, which means much much less noise.
Of course since they use two wires for the differential signal there is
only room for either left or right on a single plug.  So you need a pair
of plugs (just like consumer stuff often has white/red or white/black
pairs of RCA connectors to carry left and right except those connecters
are only two conductor each.).

So a balanced 1/4" and a stereo 1/4" may be physically identical, but
their use is different.  A balanced 1/4" is essentially a mono 1/4" with
an additional connection for the differential part of the mono signal.
This is why you need a left and right balanced connector to get a stereo
signal (and hence the Y adapter connects to left and right balanced to
provide a single 1/8" stereo jack).  In fact emu says that if you have
equipment that supports unbalanced audio with mono 1/4" jacks, you are
allowed to connect that with 2 conductor 1/4" patch cords (with TS
connectors rather than TRS connectors) to the balanced jacks, and it
will simply not use the differential part of the signal (since the cable
won't carry it).  Either way, they are mono jacks on the emu card.

> I'm just being lazy - I downloaded a tar.bz2 file - I'll look for
> instructions and install it from that. Again, should I bother - my card
> is "working" - will it work better with 1.0.14?

Does dmesg say it loaded the 'hana.fw' file?  I believe the main PCI
card works without it, but the companion card needs the firmware file to
work.  Lots of emu products use the same emu10002 based card but have
different companion cards or external boxes to provide different
features, all of which use firmware files to enable them.

--
Len Sorensen

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