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How many audio channels over 1 pin spdif ? (x-fi)



 
 
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  #1  
Old November 24th 18, 05:38 AM posted to alt.comp.hardware.pc-homebuilt
[email protected]
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Posts: 533
Default How many audio channels over 1 pin spdif ? (x-fi)

Hello,

Take a look at this picture, it shows pins for audigy and x-fi elite pro soundblasters:

http://pinouts.ru/visual/gen/sb_audigy2_ad_ext.jpg

ascii version in case picture is no longer available:

2 40
.....................
.....................
1 39

pins seem to be numbered vertically from bottom to top 1, 2, then next column is probably 3 4 and so forth.

Not sure which pins would be important to make a custom cable.

pin 5 spdif 0 in

pin 9 spdif 0 out
pin 27 spdif 3 out
pin 29 spdif 1 out
pin 31 spdif 2 out

Which other pins would be important ?

It mentions these SPDIF output pins. 0,1,2,3

So that's 4 pins.

How many audio channels can travel over 1 pin ?

Also how would these be connected into a cable, should gnd be included or another other pins

What I am trying to figure out if the X-Elite Pro soundblaster is what I currently believe it is:

7.1 Surround Sound Analog outputs
5.1 Surround Sound Digital outputs

However if only 4 spdif pins available then how would it achieve 6 channels for 5.1 surround sound digital ?

I read somewhat 1 spdif connection via normal connectors/cables can carry two audio channels.

So this ad_ext connector has 4 spdif pins, is the x-elite pro soundblaster perhaps a 7.1 digital output device after all ? But hampered/nerfed/capped by cable design ?

Currently I am investigating sound quality of laptop/hdmi digital vs dreampc2006/x-fi analog both to same receiver (denon 1909).

The digital connection from laptop is remarkable... it produces very high quality sound, sharper/more so than the x-fi analog signals.

So I am very interested in trying to connect the x-fi digitally.

I will most likely purchase spdif cables fiber optic and coax from a local shop if they have it and they probably do. I will purchase these mostly to see if there is indeed a big quality difference in audio signal between analog and digital from x-fi. I am starting to believe this is indeed the case..

So even testing x-fi 5.1 surround sound would be interesting to see quality differences.

Currently the laptop hdmi receiver setup is not producing surround sound correctly.

This is probably caused by the receiver being in 7ch stereo mode which is wrong.

This simply duplicates a stereo signal over multiple speakers which is wrong I believe.

For example the "rear right" signal can also be heard on the "right speaker" this is wrong, the "rear right" signal should only be heard on the "rear right speaker".

I think I know how to configure the receiver to select/set a different surround mode, it may have to be channel direct, or perhaps dolby digital ext/plus that sort of thing.

I will experiment with that tomorrow to see if correct surround sound can be produced from the laptop via hdmi to receiver.

This annoyed me when playing world of warships or company of heroes on the laptop... the direction of sound didn't seem right at all, so it was noticeable.

I must say the x-fi elite analog setup worked much simple straight out of the box into the receiver basically, so for noobies the analog setup is much easier to get working correctly.

Creative was smart to seperated the 8 channels into 4x2 stereo signals... the receiver I think sends this forth to the speakers. However this signal is probably not digital hence some signal loss from digital to analog convert and back to analog to digital convert dac/cad

Today I spent many hours doing experiments and getting to know my receiver better and being able to configure it with just the 1 or 2 line display on the device itself instead of on screen display connected to monitor... cable probably too short anyway but I also wanted to learn to operate this device from itself without any other devices. I kinda like these technical challenges, guess it's my experience and age and mindset/determination to get it working, "failure is not an option" mindset from playing all that world of warships lol.

Also my x-fi elite pro came with this breakout box as I called it or as some call it official name now is i/o console. It also has spdifs... but only two spdifs out...

So are these the 4 pins from the ad_ext going to the breakout box ? forming two spdif outputs on it ?

What I also wonder about is the "flexi-jack" it can also be configured as an digital i/o.

Probably a spdif output.

It can work via RCA to mini cable or something like that.

So is this again the same 4 pins, perhaps 2 of them going /inout of that flexi jack ?

Or is this yet 2 additional spdif pins ?!?!?!?

So what is the actually ammount of spdif output pins/channels that this x-fi elite can do ?

Is it only 4 spdif pins output ?

Or is some whacky combination of:

ad_ext 4 spdif pins + digital i/o flexi jack possible ?

Perhaps resulting in a hardware/connection-wise output possibility of 6 spdifs outputs ?!?

Let's assume for a moment that this would be possible, would theoretically this be enough for 7.1 channels ? Or are 8 spdif pins neccessary for that ?

So this is where I am somewhat confused ?

Perhaps 3 signals can go over a 2 pin spdif output connector thanks to dolby/dts compression ? How does that work ? Same question as in beginning but kinda filling in the possible blanks here myself... which could be totally incorrect.

Bye for now,
Skybuck.
  #2  
Old November 24th 18, 09:44 AM posted to alt.comp.hardware.pc-homebuilt
Paul[_28_]
external usenet poster
 
Posts: 1,467
Default How many audio channels over 1 pin spdif ? (x-fi)

wrote:
Hello,

Take a look at this picture, it shows pins for audigy and x-fi elite pro soundblasters:

http://pinouts.ru/visual/gen/sb_audigy2_ad_ext.jpg

ascii version in case picture is no longer available:

2 40
....................
....................
1 39

pins seem to be numbered vertically from bottom to top 1, 2, then next column is probably 3 4 and so forth.

Not sure which pins would be important to make a custom cable.

pin 5 spdif 0 in

pin 9 spdif 0 out
pin 27 spdif 3 out
pin 29 spdif 1 out
pin 31 spdif 2 out

Which other pins would be important ?


Start with Wikipedia.

https://en.wikipedia.org/wiki/S/PDIF

You should use the proper "accessory" with your sound card.
If there is a front panel accessory, a box with a ribbon cable
intended for that connector, then use it.

SPDIF is digital. It runs at 6MHz. It can carry stereo (two channels).
It can carry encoded content (AC3) which unpacks to 5.1 sound.
It can also carry four channels without coding, but the resolution
uses half the bits. I've never seen any practical examples of the four
channel mode being used (no one is crazy enough to use it).

From a quality perspective, only the two channel mode is worth using.

I've never noticed any AV receivers in my travels, with four SPDIF
inputs, so I don't know why they'd have four of them like that.
Perhaps some Creative product has four SPDIF inputs ?

*******

If you're a hardware hacker, there are at least three ways
to send the signal.

1) The proper way, is transformer isolated, 0.6Vpp. 75 ohm coax
cable, RCA connector perhaps. Home theater systems or
older AV receivers, might use the proper interface. Transformer
isolation (similar to what Ethernet uses), removes grounding
differences as an issue. I think we had a discussion once, about
the abnormal grounding in your place.

2) The signal on the 40 pin cable, could be 3.3V TTL levels.
It might not be intended for driving a 75 ohm coax cable
directly. That's why you'd want to see the circuitry on the
Front Panel board for the sound card. A circuit is needed
to convert the signal on the 40 pin, into something the
AV receiver can use. It would be typical to put the "cheapest"
signal on the connector, and then the device receiving the
signal (the Front Panel board) is responsible for conversion
into a proper signal.

3) Converting the 3.3V signal to TOSLink using a $1 LED transmitter,
is typically the best means of delivering the 6MHz digital signal.
The TOSLink plastic fiber optic cable solves the ground loop problem.

With four S/PDIF you could send 8 channels in good resolution. But
I've never seen such a thing done with audio equipment. No pictures
of such.

*******

You're delusional if you think the SPDIF receives a different
signal than the analog channels do. When you use the analog channels,
you are using the Creative DAC chips, whatever they used for
conversion of the digital signal to analog. They're probably
damn good DACs. That's probably not the weakest link.

The worst part of a Creative product, is the DSP treatment
of the audio, before it's sent anywhere. One other poster
referred to this as "digital mutilation". That's because
they do stuff like add echo/reverberation, to give "depth"
to the signal. You should not do that to all music types.
Applied to a piano recording for example, the results could be
"muddy" sound.

Some sound card drivers, the "Special Effects" setting of "None",
doesn't work. A test shows the card is still adding concert hall
reverberation effect to the output signal. This is the part
you need to get rid of. I only studied this, because the sound
I was hearing was muddy. Sending test signals using Audacity
on one computer, and recording the analog output via LineIn
on a second computer, is how I discovered the "Special Effects"
were still enabled.

It's not the DACs on the Creative card, but it could be
the reverb. That would be just one example of "mutilation".

Paul
  #3  
Old November 24th 18, 12:37 PM posted to alt.comp.hardware.pc-homebuilt
Flasherly[_2_]
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Posts: 2,407
Default How many audio channels over 1 pin spdif ? (x-fi)

On Sat, 24 Nov 2018 03:44:33 -0500, Paul
wrote:


They're probably damn good DACs. That's probably not the weakest link.

-

Many more MBs have audio chipsets that are now to where standards
equal to the dedicated soundbaord, rendering it redundant from a
baseline perspective of audiophile-grade stereo signals.

There is also that same issue with another board, I use, adding native
chipset reverberation delays. It took an OEM driver utility to fix
and turn it off.

I really can't place a developer's mind, when the driver and utilities
include, usually for the only effects, several reverberation-class
delay parameters, randomly labeled as much for "features", even with
an audacity to title one such for a "Sewer Pipe".

Probably because an average user wouldn't go much beyond a minimum to
reproduce sound from a MB's soundchip. Somewhere between what's
allowable as "cute", and bold package lettering for advertising the
MB's audio performance. Consequent software audio and DSP modules may
then mean little if anything -- so a "Sewer Pipe" it is, as far as the
purchaser will go; ... who's could not then care if, at a
driver-level or minimum install, in addition, that a delay is
effectively hardcoded. Or that Creative, given existing interests to
include an OEM support with the resources to turn off an aesthetic
appeal for discerning listeners, to concordantly murmur over a
toilet-bowl being flushed.

Then again, the software, specifically, made my one and only Creative
Labs soundboard, a first choice to buy one, my last upon gratefully
replacing it with a Xonar series.

I use quad-duplicate stereo imaging and an additional TOSlink LED
carrier for two more, or six active channels being duplicated over a
single stereo source processing;- the TOSlink may be optionally
defined for its own sampling rate. There are, additionally, more
progressive options for modern theater usages, with dedicated
equipment for more channels, although I'm not interested in going
there. The TOSlink "seems muddiest", a bass definition for corrective
measures to speaker limitations, (rear passive radiators: "drum-skins"
in non-ported "Eastcoast" engineering), although a straight mixer
input from a DAC unit. That could possibly change with signal
rerouting, or auxiliary hardware processing, both
compression/expansion and EQ-ing, on each pair of the quads. Notably
a bad EQ pot and unacceptable noise from my first attempt to resolder
it for a by-pass condition. I'll recheck the soldering and possibly
swap a working low-pass filter pot, or I've another piece of Chinese
assembled gear that was built to take a crap. Or not: Mixer pathing
shouldn't matter for a base duplicity between either soundboard
stereo analogue outputs, and the DSP TOSlink's and an assumed fidelity
from the inline DAC unit.

(The last dedicated EQ, this one replaced, was entirely from a
digitally controlled interface screen, no sliders, and had its own
dedicated TOSlink input.)
 




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