optical out sound card for linux?

[Lennart Sorensen]

On Sat, Jul 07, 2007 at 08:29:45AM -0400, tleslie wrote:
> I just upgraded my Sennheiser HD570 to the new HD650 their best head
> phones.
> 
> Now plugged into my SB live sound card,
> the high energy song mixed with huge bass cause the
> headphones to make that bass sound like someone 
> hitting a shoe box with a hammer, its bad.
> 
> I read that with highest end head phones, they are 
> "extremely high impedance headphones"
> and they can suck large with cheap 
> sound amps, and I am guessing a sound blaster
> card is just that.
> 
> So i am going to buy a bithead head phone amp
> that is suggested as a cheap amp (400$) for a HD650
> (good ones go for about 4-5K$ and I ain't going there 
> now),
> so I want to feed the head phone amp with a optical
> input, and thus have a optical output
> from the sound card.
> 
> Has anyone in the group used a sound card on Linux
> with optical output?
> Does it "just work" ?
> Anything special I need to do or know,
> any recommended cards?
> Obviously the card needs to work well with Linux.
> 
> I assume that the card would just act as a digital pass through,
> not distorting the sound in any way by cheap analogue electronics?
> I am seeing references to digital sound over USB,
> anyone ever do that on Linux ... I have never even heard of that before,
> and wondering if it is just a windows only device driver thing.
> 
> Until I get this fixed, I have to avoid playing certain songs :(
> So ironic, get a amazing headphone, and can't play as much music with
> it until paired with an amp, I guess even if i researched and found this
> out before hand, i still would have bought the HD650, I just would have
> bought a amp at the same time!
> 
> as an aside, any one comment on how much better a 5K$ headphone amp is
> over a 400$ one? I am hoping this is a case of 400$ gives you 99.1% 
> and the 5K$ gives you 100% and is only worth it if you have money to
> burn, and that in general there is almost no difference.

Well digital has a few issues too.  You essentially have to convert
everything to a specific bit rate, and since conversion always causes a
loss of quality, that isn't too nice to do either.  After all if you
play an mp3 that is 44.1KHz, and send it across a 48 or 96khz digital
link, something has to convert the 44.1KHz signal into a 48 or 96KHz
signal.  Some conversion algorithms are good, some aren't.

A number of cards have digital support.  Alsa supports iec958 (spdif) on
a lot of sounds chips.  If you tell your software to use that port, then
the analog part of the sound card isn't really involved at all, but your
software has to send valid data for spdif.

You might want to instead just run the output of the sb speaker/line out
to an external amp, and set the amp on the sb live to 0dB (whatever
setting that is in the mixers range).

Of course make sure you didn't accidentally enable the
bass/treble/othercrap equalizer on the sb live.  In general I find my sb
live to have very good sound quality, although I am only using $100 head
phones with mine (using the front 1/4" head phone jack on an sb live
platinum which is specifically designed for headphones).  It is quite
likely though that the sound quality on the sb live is good, but the amp
starts to distort at high volume levels (which I guess you might need
with high impedence head phones) in which case just using an external
amp from the analog output would solve the problem.  It is also possible
a low end sb live doesn't sound as good as the high end ones does (even
the connectors on the low end one were plastic, while the high end used
gold plated metal connectors with much more solid contact).

--
Len Sorensen
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