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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.


[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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