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Long range music server
Strav
post Jan 28 2010, 12:15
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He. I'm planning to build a rather decent sounding system where the source will be a either mac or pc based server. Now the main constraint is to route 3 different stereo signals to 3 different amps, each on a different floor.

Here are the solutions I'm considering (some might be obviously wrong, as I didn't find the proper information, any correction is gladly welcomed!):

1.
- Use as many as it takes, on-board (or preferably external) audio card with coax s/pdif outputs such as m-audio delta 66 http://www.m-audio.com/products/en_us/Delta66.html
- link it to the amps with low as possible impedance coaxial s/pdif cables.

2 (if that's even plausible).
- Use a/several pci card(s) that could output data through a fibre optics cable
- link that fiber optic cable through an optic capable DAC, then link it to the amp.
(if someone could explain me the whole concept of an optical s/pdif output on an audio card, why would that be needed if you need to convert the digital optical link to analog for the amp?)

3.
Same as 2 but using Usb cables and hubs to usb capable dacs.

From what I've read on the limitations of optical links (6meters max), perhaps I should discard this option.
If anyone can give me some advice on the best possible (yet affordable) way to get a clean signal from the source to the amp, that would really be appreciated. (btw, couldn't I use some device to perhaps regulate the signal in the coax cables half-way through?)

many thanks in advance!

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Skelsgard
post Jan 28 2010, 13:54
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If you're plannig on having one computer to ruled them all (sorry, stupid joke) then that Delta66 seems like a good choice. You would select which spdif output to be used when you'd want either A, B or C amp receiving the signal.
As for the connection, I don't think that USB cables that long are available, at least not longer than 6 meters.
Coaxial SPDIF would be your choice for affordable and if you're not convinced with the quality of SPDIF cables for sale than you can make you own, after all it's just a single mono RCA wire. You get a decent cable, get the plugs, build it and you're done. No more requirements needed than knowing how to weld with tin.
As for the quality, SPDIF is a digital signal so if the quality is bad then the amp won't understand the signal and won't be able to decode it, unlike analog which can have bad quality but it will still be audible.
So if the cable quality is decent, then the signal should be indistinguishable than that one carried by a high-end top notch overly priced SPDIF cable.


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pdq
post Jan 28 2010, 14:18
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QUOTE (Skelsgard @ Jan 28 2010, 08:54) *
As for the connection, I don't think that USB cables that long are available, at least not longer than 6 meters.

You can easily string multiple USB cables together, as long as you place an inexpensive USB hub at each connection. There is an upper limit to how many hubs you can place in series, something like four, I think.
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Qest
post Jan 28 2010, 20:22
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My whole house is wired for cable (good old RG-59). My music server with coaxial S/PDIF output (Musiland 01 USD, but a Creative 24-bit Live! card before that) is in the basement and I just bought a converter and plugged the S/PDIF into the cable, then hooked up my living room (one floor up and across the house) to my basement at the hub in the garage. Moral of the story: never had any problems with it.

So you could consider that if you have the infrastructure.
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Strav
post Jan 28 2010, 21:03
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Thanks for your answer, but I need a clarification. I thought everything that came out of an audio card (along with s/pdif), was an analog signal ready to be used by a plain dumb amplifier - since the job of an audio card is to convert digial to analog right? The whole point of using a pci audio card, was to avoid, in the end, to buy separate DACs for each of my amps. Now let say using s/pdif, I still must decode the signal before passing it to the amps, is there any way, while still using only one computer, and perhaps avoiding the usb/multi-hubs solution, to route the digital signal to those, in the end, unavoidable external dacs?

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Qest
post Jan 28 2010, 22:41
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I am afraid you are mistaken.

While most of a sound cards outputs are analog (and yes, "ready to be used by a plain dumb amplifier") S/PDIF outputs are digital and 'bypass' the digital to analog portion of the sound card.

If you are sending a digital signal out of your PC then you will need a DAC at each stereo - be it a separate component or built into the receiver/amplifier/whatever. This isn't necessarily a giant hole in your wallet though, there is such a thing as a cheap DAC.

If you use the analog outputs of your sound card(s) then you won't need a DAC at each stereo, just an amplifier, but there may be some degradation in the sound from travelling across your house. Someone else may be able to tell you more - I've never experimented with long analog signal runs, myself.
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Skelsgard
post Jan 29 2010, 00:22
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S/PDIF stands for Sony/Phillips Digital InterFace.
If you plug an SPDIF signal to a standard audio input in a receiver you'll get noise.
SPDIF can send AC3, DTS or PCM audio in digital form, to be decoded by the receiver. I believe it can carry up to 4 channels of PCM audio (a standard WAV file).

QUOTE (Strav)
Now let say using s/pdif, I still must decode the signal before passing it to the amps, is there any way, while still using only one computer, and perhaps avoiding the usb/multi-hubs solution, to route the digital signal to those, in the end, unavoidable external dacs?


Yes, but it depends on what you want.
If you want to have all 3 amps to get the same signal at the same time, then you'll need either 1 audio card with al least 3 SPDIF outputs and the possibility to control which output is being used (1, 2 or all 3) or 3 separate cheap audio cards with single SPDIF outputs, and software (player) to handle the sending of several signals thru several audio cards/outputs (most don't).
If you want to use 1 amp at any time, then you'll need the same card/s as above and any player that supports SPDIF output thru selection of a specific audio device (most do).

I've tested with the SPDIF output of my soundcard connected to the SPDIF input of a Sony amp with a RCA-to.-3.5-jack plug connected to a 10-meters decent quality RCA cable (built by myself) connected to another 1.5m RCA cable and the signal was decoded flawlessly, either AC3, DTS or PCM.
Considering all the unnecessary connections you would expect some loss of quality, yet there was none.

This post has been edited by Skelsgard: Jan 29 2010, 00:23


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yerma
post Jan 29 2010, 08:35
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Just curious, is the transmission of audio signals via long cables a prerequisite? Otherwise I would suggest a network based music distribution system like Squeezebox or Sonos...
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Strav
post Jan 29 2010, 11:25
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First, thanks for the advices (and the clarifications that came with them)!

Although I feel it's a shame to buy an audio card just to output via s/pdif, it seems now I have to look at what I can get from modest priced dacs.
To answer your question yerma, yes I did thought about using some kind of networked thin-client architecture thanks for mentioning it - I'll certainly have to weight the two setups before taking any decision.

Nice reading you people.

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