Stereo vs front left & right channels from 5.1/7.1

Napalmhardcore

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I know this sounds a stupid question (and probably is) but here goes.

Using a PS2/3 you have composite/component out with the red and white for stereo (or in the case of PC, a 3.5mm to red and white RCA). Particularly in the case of the consoles (being there are not other outputs to supplement this method) it is intended as a stereo connection. When you use another method such as HDMI or digital optical, it may be sending out a 5.1 or 7.1 signal. If you have stereo speakers only and were using one of the various bitstreams or PCM with 5.1/7.1, and were using no DSP effects to emulate surround (what my AV receiver calls straight decode), would the sound coming from the speakers be the same information (ignoring sample rate and bit depth) as that of the signal specifically intended for stereo?

As I said I know it sounds stupid, but I've not been able to find any info that clarifies this. I just wasn't sure if because a dedicated stereo output wouldn't be able to rely on the other channels to provide sound it may carry more information (such as some of that which would go to the side speakers in a 5.1 setup).
 

ssddx

Glorious
Moderator
you mentioned that you have an AVR.

it knows how many speakers you have hooked up and will decode accordingly.

you will get 2.0 sound if you only have two speakers hooked up regardless of if you hook up to it via hdmi, optical or rca/component.
 

Napalmhardcore

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What I was getting at is, if you use only two speakers (or 2.0 I guess) out of a 5.1/7.1 signal, is that the same as using stereo from a connection which can only do stereo (like the left right signal from a composite/component connection)?

BTW ssddx, you helped me recently. I'm the guy who asked for advice on what I needed for my setup, for which I'm grateful :)
 

ssddx

Glorious
Moderator
so by that i take it you are asking....

is using a HDMI (single plug) connection the same as using composite (rd+wh+ye) or component (rd+bl+gr+wh+rd) or OPTICAL/COAX+one of the previous for video feed?

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the answer is both YES and NO.

does it accomplish basically the same thing? YES, you will get stereo sound.

is the quality of the signal the same? NO, going digital (either optical or hdmi) is going to give you a better signal.

also... in the case of getting soiund from a pc it would be best if you do NOT double amplify. the headphone out port is amplified (since it needs to power unpowered 2.0 speakers and unpowered headphones) and your avr is amplified (since it also powers unpowered speakers) so you could get some signal distortion. using a line-level output is a better idea than this. honestly i would only go this route if you have a soundcard which has "virtual surround" capabilities and you want to use it with your AVR. if not... then i would go digital instead.

going optical fixes the problem of signal quality however its also limited to compressed DTS audio for surround sound. only 2.0/2.1 sound is available as uncompressed PCM. basically... if you add any more speakers to your setup your sound quality is going to be less using optical than hdmi. as it stands now it would be about equal.

remember you not only have to worry about the AUDIO but also the VIDEO content as well. if you have HDMI and can use it....then i suggest doing it unless there is a definite reason for not doing so. those reasons would be 1) you want to use the virtual surround capability of your soundcard or 2) you have a strange multimonitor config and dont want to run one of the monitors through the AVR because you are worried about some sort of delay in comparision with the other monitors or 3) the avr is located a fair distance away from your pc and you need to run a long cable to it in which case a direct passthrough of hdmi wouldnt make sense given the distance.

running one hdmi cable as a passthrough is a bit neater for cable organization provided its close to the pc and it is a 100% no issue solution with a ps3 since are no issues. with ps2 the best you are going to get is component cables (rd+bl+gr+wh+rd) so you should use that (provided you can take that as an input to your screen)

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sorry if i forget the details of your setup..... (you could link me to that post if you want) as i go through so many posts its easy to forget names and details without re-reading.

also... you will not be missing out on sounds. instead of coming out the 1x center, 2x front and 2x rear all the soundwill come out your 2x fronts. basically it is all compressed into 2.0 sound. the only way you would be "missing sounds" is if you have your system set up on your AVR as a 5.1 or if you have your windows settings as 5.1.


TLDR: 3.5mm to rca works... however there are much better ways to connect provided there arent valid reasons for going with 3.5mm over those ways which i described above. in any case you would want to use a line level output not the headphone jack.
 

Napalmhardcore

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I think that's the answer I was looking for. Over the last week I've learned a lot about different audio signals and was aware of the limitations of sample rate and bit depth of optical for example.

Basically what confused me is page 38 of the manual, where it says about straight decode mode. With straight decode, it seems it would be sending the front left and right speaker only the information for the front left and right channels as it would in a 5.1/7.1 setup. Basically I wanted to know if that is a thinner mix of sounds than you would receive from something which was intended to be stereo in the first place. The tread in which you helped me is here.

I am not double amplifying, currently just running stereo out to my AVR from the PC and HDMI for PS3/4. I have another reason for not running HDMI from my PC through the receiver which is that, I regularly play older video games and the receiver only outputs particular resolutions, but I need access to resolutions such as 1600x1200 etc for titles that don't support widescreen.

BTW, it will soon be redundant (as I have more equipment on the way) but I am curious anyway. When using an analogue output from PC, what is the optimum bit depth and sample rate to use? While the Speakers will produce sound when it is set to 24 bit, 192 KHz, I'd imagine it doesn't actually get the full benefit (otherwise there would be no reason to go digital).
 

ssddx

Glorious
Moderator
oh. now i remember that other post...

you say that you arent doubleamping.... are you using a line level output connection? that is what you should be using (if you even have one).

also why arent you using spdif optical out (or hell... even spdif coax)? for 2.0/2.1 it is just as good as hdmi. the only reason i can see not to use it is if you have your sound card doing "virtual surround" processing.

use the high bit depth. that isnt the main difference between digital and optical. remember that headphones and speakers can benefit from a higher bit depth too and those are analog connections.

the first difference is that digital isnt as succeptible to electrical noise from other components as analog is. this means that you wont get buzzing, whining or other electrical noises from distortion which could happen with unshielded analog connections in close proximity to EM sources.

the second is that digital is processed by the device you are sending the digital signal to (your receiver) instead of the soundcard in your computer. this means that if you have a cheap sound card or onboard sound aboard the motherboard and you have a spdif optical or coax connection you can send the data for processing by the receiver instead. this is why if you are using a high end sound system you really dont need a high end sound card. in fact this is what i do. my $1300 sound system is hooked up via my video card (basically it does the same thing... the sound data is exported to the avr). i dont think i even have my asus motherboard audio drivers/software program installed since i dont use it. sounds are generated and processed when in game and directly sent out to the receiver for processing (normally in dolby or PCM)
 

Napalmhardcore

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I assume it is line level that I'm using. I've always run out to powered speakers and have never had any noticeable noise or anything. Here is a picture of the outputs. I use the green, front speaker out connection. Also as you can see, no optical out, and it's only since my AVR arrived that I've had the means to connect digitally. Originally I was going to use the HDMI for audio. It was only after setting everything up that I realised it wouldn't be viable (resolution restrictions). I have a Sound Blaster Omni on the way as well as a DSS-2. I realise the AVR can emulate surround, but it will be messy routing wires so they aren't in my way and using extensions every time I want to use it, so the DSS-2 should come in handy.

As for the PC analogue question, what sample rate? Or is it just a case of, as high as one wants but due to the nature of analogue it will be prone to interference?
 

ssddx

Glorious
Moderator
the lime connector (front audio/headphones) is listed as line-out in your manual so i guess it is a line-level output as well..

it looks like you do have spdif coax though (which is digital)

what do you mean messy with wires? it would only require a single wire to the avr. headphones are always nice, but its possible to have both as an option depending on where your avr is.

a good soundcard has the ability to emulate surround sound. which might work out better for some games. not sure how well an avr does at such emulation though.

pretty much hit that right on the head. i've heard that higher sample rates also affect the bass output your speakers (either connected via analog or digital... since its a windows setting) have.

nothing wrong with analog... (after all speaker wire through the walls is analog) howevever just by the nature of how it works its more succeptible to interference. most of this is going to be caused at the source (ie from the electrical noise inside your computer or other devices) but its possible to be affected by outside sources if the em strength is high enough. generally that isnt the case though.
 

Napalmhardcore

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I have a pair of PX-21's for use with my PS3/4, both of which sit in a compartment to the right hand side of the desk (intended for a PC but my case is too tall). The cable for the headphones ends in a split, one side the USB connector, the other a 3.5mm headphone jack. My AVR is on a shelving unit to my left (top shelf). I'd either have to connect the headphone jack to the AVR (which would require a 6.3mm adapter), then run a USB extension from the PS3/4 to the USB connector on the headphones (for power and chat). Alternatively I could plug the USB connector (from the head-set) directly to the USB port on the PS3/4 and have a stereo extension cable running to the AVR. Either way there will be a cable going across.

I've never really had much trouble with analogue interference. Though seeing how I have the Sound Blaster on the way it shouldn't really be an issue anyway. The Sound Blaster will also allow me to use my AKG headphones for gaming on my PC as it has a built in mic. Also it has Dolby Digital Live, which as I understand it is required for the DSS-2 to process surround.

Thank you for taking the time to answer my questions, I really appreciate it :)
 

ssddx

Glorious
Moderator
i wouldnt be plugging those kind of gaming headphones into the receiver 1/4 output for fear of blowing them. receiver headphone amplifiers can pump quite a bit more power out than a 3.5mm or usb jack.

i would be connecting them instead to the source device (pc, ps2/3/4). i thought by clutter you meant that you couldnt hook all of your devices up to your receiver (not the sharing one pair of headphones bit).

in many cases you wont hear audio interference. its only a "could happen" scenario. i would still probably use spdif out though unless you want to have the sound card process "virtual surround" for games on those speakers of yours. your call of course.

no problem. dont forget to click the big green button if i answered your question.
 

Napalmhardcore

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I'd not actually considered the possibility of blowing the PX-21's, however it never seemed like an elegant way of doing it anyway. When it arrives I'm planning on using the optical out from the Sound Blaster Omni to go to my receiver.

The DSS-2 will be fit for purpose. I don't think the Sound Blaster Omni does virtual surround so I think I'll need to either use the DSS-2 with it or, have the optical go into my AVR and use the silent cinema with my AKG headphones (although as you mentioned, I don't know how good that will be compared to the DSS-2, which is specifically designed to emulate surround).

It would have been nice if the Sound Blaster Omni worked with the consoles (as the Sound Blaster Recon3D does), as it would have allowed me (if I so wished) to use my AKG headphones and use the built in mic (on the Sound Blaster) for chat. I think I'm going to be happy with what I've got for a while anyway. When and if I want to upgrade I'll look at what's available at the time.

Thanks again.
 
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