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Old 11-25-2004, 04:49 AM   #1
Gabriel Torres
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Default SPDIF Connection

There has been a new article posted.

Title: SPDIF Connection
URL: http://www.hardwaresecrets.com/article/82

Here's a snippet:
Many users and technicians must have already noticed that CD-ROM drives have an output called SPDIF and many sound cards, especially the more expensive sort, also have a connector labelled SPDIF. But ...

Comments on this article are welcome.

Last edited by Gabriel Torres; 07-20-2012 at 07:54 AM.
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Old 04-27-2009, 06:13 PM   #2
Cee Jay
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I am no expert in digital audio connections, but after reading the S/PDIF article, i was left speechless. Is not S/PDIF a two channel digital audio format, as opposed to the digital bitstream audio that is supplied as the standard black or orage connector on the back of home theater receivers/DVD players, etc?

My dillemma is this. I have 6 JBL studio monitors and two monitor subs, all with one S/PDIF input and one output each, among others, such as analog and AES/EBU(digital XLR). I want to connect them to some sound card to have surround audio from a PC. I first (without having learned about S/PDIF) tried connecting the digital output from the DVD player to the front left speaker, then daisy chaining them all around to the other speakers via S/PDIF inputs and outputs. Uhhhhhh.....no way. Didnt work. The best that I could get was stereo.

After much investigation and research, I learned that S/PDIF is only a digital pair, and carries only two signals, say a left and right, a center and sub, rears, etc. Not all of the surround signals could be transmitted through one S/PDIF cable.

I then learned that you need MULTIPLE S/PDIF outputs, usually 3 of them, assigned as L/R, C/S, RL/RR. VERY high end equipment such as the Meridian G61R pre-amp have these, but those cost 8K and up.

So........how to connect these speakers to a PC. I need multiple S/PDIF outputs. Your article suggests that the "orange" outputs are S/PDIF outputs, but they carry more than a digital pair of signals. They carry all of the channels, no????? Is there not a difference?????? Help please.
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Old 10-13-2009, 04:00 PM   #3
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Default SPIDF Help

ANYONE??? Can anyone help me with this?
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Old 10-27-2009, 08:10 PM   #4
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Hello Cee Jay,

Sorry about not answering you before, for some reason I didn't see your original post.

Quote:
Originally Posted by Cee Jay View Post
I am no expert in digital audio connections, but after reading the S/PDIF article, i was left speechless. Is not S/PDIF a two channel digital audio format, as opposed to the digital bitstream audio that is supplied as the standard black or orage connector on the back of home theater receivers/DVD players, etc?
Both are the same thing. SPDIF is the name of this digital connection you are talking about; the black connector you mention is probably the optical connector (Toslink) and the orange connector is the coaxial connector.

Quote:
Originally Posted by Cee Jay View Post
My dillemma is this. I have 6 JBL studio monitors and two monitor subs, all with one S/PDIF input and one output each, among others, such as analog and AES/EBU(digital XLR). I want to connect them to some sound card to have surround audio from a PC. I first (without having learned about S/PDIF) tried connecting the digital output from the DVD player to the front left speaker, then daisy chaining them all around to the other speakers via S/PDIF inputs and outputs. Uhhhhhh.....no way. Didnt work. The best that I could get was stereo.
Of course it won't. The digital connection will carry a bitstream representing all the six channels. You will need to either find a way to configure each speaker to "tune in" to a certain channel (i.e. find a way to configure speaker 1 as front left, speaker 2 as front right, and so on) or to use a some sort of device to make this separation for you. If you post here the exact model you have I may research this for you.

Quote:
Originally Posted by Cee Jay View Post
After much investigation and research, I learned that S/PDIF is only a digital pair, and carries only two signals, say a left and right, a center and sub, rears, etc. Not all of the surround signals could be transmitted through one S/PDIF cable.
This is not correct. This connection will carry all channels available. Otherwise a single SPDIF connection between a DVD player or Blu-Ray player and a home theater receiver would only play stereo and you would need three wires, which is not the case (only one is needed).

Quote:
Originally Posted by Cee Jay View Post
I then learned that you need MULTIPLE S/PDIF outputs, usually 3 of them, assigned as L/R, C/S, RL/RR. VERY high end equipment such as the Meridian G61R pre-amp have these, but those cost 8K and up.
As explained, the problem is that you need to find a way for your speakers to "catch" the right signal from the digital stream. If they do not have a configuration switch on themselves to configure each one of them as front left, front right, rear left, rear right, the only way is by installing a device like the one mentioned. Probably your speakers do not have such configuration because they are intended to work under stereo mode only.

Quote:
Originally Posted by Cee Jay View Post
So........how to connect these speakers to a PC. I need multiple S/PDIF outputs. Your article suggests that the "orange" outputs are S/PDIF outputs, but they carry more than a digital pair of signals. They carry all of the channels, no????? Is there not a difference?????? Help please.
Explained above.

From all you posted it seems that the problem is with your studio speakers: they were designed to tune in only to the front left and front right channels only, because they were projected to be working only on a stereo environment, not on a 5.1 config. If you post the exact model we can download the manual and take a deeper look.

Cheers,
Gabriel.
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Old 07-18-2011, 07:33 AM   #5
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Default Sometimes analog is better!

Quote:
Therefore, it is always better to transmit audio in digital format.
Wow - that's a little over-simplified, both in theory and in practice.

It is true that a competently designed digital interface like SPDIF or HDMI will always transfer a DIGITAL signal with 100% accuracy and zero noise (or not at all) that does not mean that an ANALOG signal such as sound will be transferred either noise-free or distortion free (two different issues). It depends on the bit-rate used and the quality of the converters. Given that the bit rate of SPDIF and HDMI is high enough to out-perform all but the most expensive analog systems, that is not an issue in this case. Since we are only talking about playback and since we can these days assume the source material is already in digital form, the quality of the digital to analog converter is the critical issue.

Practically, if you have a very high quality amplifier and a relatively low quality source (such as a cheep DVD player or the MB audio on a PC) you will be best using a digital cable between the two as recommended in this article. However if you have a very high quality DVD player and a relatively low quality amplifier, you will usually be better off using an analog connection to take advantage of the relatively better digital to analog converter in the player. The caveat is that once in the analog domain issues such as cable quality and length and the electrical noisiness of the environment come into play as well, but for most reasonably compact setups, the quality of the digital to analog converter will decide the quality of the analog audio reaching your ears.
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Old 07-18-2011, 11:33 PM   #6
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Default It's About Time!

Nice article Gabriel, and certainly needed since the S/PDIF interface is not understood or explained very well, which is why I say, about time.

The S/PDIF interface was "borrowed" for use by Dolby Digital (DD) and DTS to send the 5.1 channel (or more) compressed digital data to a DD or DTS decoder which decodes it into it's individual audio channels, which then must be converted to analog with multiple DACs (Digital to Analog Converters). The decoded digital audio data sent to the DACs uses a 48kHz sampling frequency, rather than the 44.1kHz of standard CD audio. While most audio chipsets in PCs can handle at least 5.1 channels of digital audio, the vast majority are just DACs, and will not decode DD or DTS encoded digital audio streams. Additional software and usually hardware (chip) is needed to decode the DD and DTS data streams, which are different, incompatible formats. The Sound option in Windows 7 allows you to test a PC's capability and configuration for decoding the DD and DTS formats.

The main thing to remember is that while the S/PDIF interface is used to carry both CD digital audio data (known as PCM) and the two formats of digital surround sound, Dolby Digital and DTS, CD audio data only needs to be processed by a Digital to Analog Converter to create an analog signal. DD and DTS must first be decoded from their proprietary format into 5.1, 7.1, etc, channels of digital audio data that are then converted to analog by a DAC.

Cee Jay's JBLs are no doubt self-amplified speakers that contain a DAC. Their connection configuration could be accomplished in several ways, and can only be learned from reading the manual, as Gabriel said. While it is possible for a system of amplified speakers to include decoders for DD and/or DTS, that is highly unlikely, as that is usually included in a Home Theater receiver, a Home Theater preamp/processor, or equivalent professional component.

At one time a few separate DD or DTS decoding components existed, but none are seen in home or PC audio today. Some PC sound cards can decode DD and DTS, and a few mother boards have that capability too, but if they don't announce that capability on the box or in the product information, they won't support it.
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Old 07-19-2011, 07:33 AM   #7
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Cee Jay, I do what you are trying to do from my PC. I have a Creative SB X-Fi Platinum with an SPDIF out to my Onkyo Tx-NR1007 receiver, that powers my speakers, all JBL Studio Series. It sends 5.1 perfectly fine to the speakers. If you want to hook the speakers directly to the PC, I don't think that's possible. If they are powered speakers, use an amp with pre-outs, just make sure it has the proper decoders to work with the X-Fi which uses Dolby Live or DTS Connect.
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Old 07-19-2011, 08:59 AM   #8
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Is there any difference in signal quality when using Toslink comparing cheap onboard solutions to dedicated sound cards?
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Old 07-19-2011, 09:07 AM   #9
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Toslink is just a connection type, onboard solutions will be identical to dedicated cards, only difference is what features are supported. Most on-board solutions won't allow the higher end codecs or various pre-mixing features. Some of the newer ones do though and are considerably cheaper than a high end dedicated card. If you want high quality analog out of the sound card, go with dedicated though.
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Old 07-19-2011, 01:11 PM   #10
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I've been looking for a simple, inexpensive S/PDIF input amplifier for the past year. I have come to the conclusion they don't exist. The closest I have found is some monitor speakers with built-in amplifiers, which is not what I want. (All I want to do is listen to music played on my Linux PC via S/PDIF. I already have some very high-end monitors, and would like to connect the PC to a S/PDIF input amp). The only other alternative is a much higher priced A/V receiver, as the low end receivers no longer have this interface.

It seems the heyday of S/PDIF inputs was almost ten years ago. Lack of standardized channels beyond stereo limits user appeal, and lack of DRM limits vendor support.

Other than stereo output for a few folks building HTPC systems for older A/V units, I'm not sure why this interface still exists on so many system motherboards. It must be cheap, and since so few test it, not the cause of a lot of returns.

If anyone can prove me wrong and point me to a cheap, good S/PDIF amplifier, please do.

Last edited by hangfirew8; 07-19-2011 at 01:19 PM.
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