Re: Digital Speakers
Kris Kerwin wrote:
Hey all.
I'm running Woody, on the 2.4.18-bf2.4 kernel. I have a ES1371 soundcard
(that's soundblaster_something_or_other). Here's the problem. Speakers work
on this box when I have it switched to Windoze. Headphones work on Windows.
Speakers don't work on Linux, but the headphones do. My thinking - it's the
speakers. They're the really nice sort - the ones with the sub-woofer built
into the system, so I'm thinking that the speakers are digital only, and
don't want to deal with an analog signal. Anyway to get Linux to output
audio in digital format, not analog? Thanx.
Kris Kerwin
Your speakers are not digital. They may be hyped in the literature as
"digital ready" (right next to the part where they sell you insanely
overpriced "digital speaker wires"), but a speaker is an analog device. [1]
Speakers with built-in subwoofers tend to have what is known as a
crossover network built into the enclosure. All that does put a lowpass
filter on the subwoofer, and a high pass filter on the tweeter (possibly
a bandpass filter on the midrange speakers).
The speaker and headphone outputs of a sound card are an analog output
(if it was a digital output, you wouldn't really need a soundcard, would
you? you'd use a serial port, parallel port, USB port, etc...). The two
ports are actually quite similar (IIRC, about the only difference is
that the headphone jack has a higher characteristic impedance of the
output stage of the amplifier...). Nothing about the Windows vs. Linux
drivers is going to reconfigure your sound card and change a class AB
amplifier into a UART or other digital device (although you could
probably fake it... would be an interesting hack...).
</bored engineer Friday discussion>
Google on your sound card model and you'll find discussion of similar
problems others have faced. A quick scan of the articles hints that the
linux driver may be messing with the volume control of the speaker output.
--Rich
[1] I recall reading an article, possibly in IEEE Spectrum, a few years
back that covered an interesting comparison of speaker wire, comparing
from both a signal integrity approach and from empirical observations by
a listener. Despite the hype, "monster cable" from your favorite
overpriced catalog didn't perform any better than 18 gauge bell wire
from the hardware store. The key factors were that power was relatively
limited (in very high power speakers systems, heavier gauge may be
needed) and that the frequency is limited in a speaker system (you can
only hear up to 20 kHz or so, which doesn't require funky twisted-pair
speaker wire or careful controls of residual L and C effects of the wire).
_________________________________________________________
Rich Puhek
ETN Systems Inc.
2125 1st Ave East
Hibbing MN 55746
tel: 218.262.1130
email: rpuhek@etnsystems.com
_________________________________________________________
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