Beginner-Need Help With SPDIF
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New member Username: SoftlyspokenmagicspellsPost Number: 1 Registered: May-08 | Hello all, I just purchased a Philips Flat screen HDTV the other day and it seems the only option for connecting my RCA sound system to it is through the SPDIF port. Can anyone explain what this really is? I purchased a digital audio cable from Best Buy (guy said it would work) and it seems to actually FIT the port, but doesn't work. I attached the cable from my TV to the "Digital Audio In" port on my home theater, but there is no audio. Do I need a different kind of cable? Or am I doing something wrong? Also, what needs to be done with the "Subwoofer Digital Audio In" port? |
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Silver Member Username: CclashhPost Number: 230 Registered: Jan-08 | Do you have a cable or a sattelite set top box? What devices such as DVD, etc.. will you be using? How many digital audio inputs are there on the RCA receiver? |
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Silver Member Username: JrbayLivonia Detroit area, Michigan USA Post Number: 180 Registered: Feb-08 | Also a model number on your RCA system would be helpful |
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Silver Member Username: CclashhPost Number: 231 Registered: Jan-08 | Jim, I cannot see your last post?? Never mind I got it... |
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New member Username: SoftlyspokenmagicspellsPost Number: 2 Registered: May-08 | Hi, thanks for the response. The RCA receiver model is RT2390 and the cable I am trying to use is the Dynex brand: Coaxial Digital Audio Cable. Also, I don't have a cable set top box, I just have a cable line running into the back of my television. I will be using a DVD, cable tv, and Nintendo Wii. There are plenty of red and white ports on the back of my RCA, but only one "Digital Audio In" and "Subwoofer Audio Out." Any ideas? |
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Silver Member Username: JrbayLivonia Detroit area, Michigan USA Post Number: 181 Registered: Feb-08 | The problem is that you do not have a cable box (or, I am assuming, a cable card on your TV), if you have the digital coax cable that you bought from Best Buy connected from your TV "Digital audio out" or SPDIF out to the RCA "digital audio in" or SPDIF in (both are orange and SPDIF means Sony/Phillips digital interface format) and you have the correct setting on the RCA then the TV is not digitizing the audio. The simplest solution may be to get a cable box that you can hook directly to the RCA. If you really do not want to do this, hooking the Red and White analog audio out of the TV to a red and white input to the RCA will work but it will not be 5.1 digital audio Hope this helps |
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New member Username: SoftlyspokenmagicspellsPost Number: 3 Registered: May-08 | Thanks Jim. I tested the same cable on the DVD player and it works great that way. I suppose I can survive with the sound system being used just on the DVD player for a while, because cash is tight. I attempted to hook the red and white analog into the tv, but there seems to be no place for it, because the back of the tv just has AV1, AV2, AV3, etc. Any ideas on that? Also, do you think there might be something wrong with the SPDIF port on the television? Should I get that checked out, or are you pretty sure it is because I do not have a set top box or sat.? Let me know, thanks for your help! |
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Silver Member Username: CclashhPost Number: 232 Registered: Jan-08 | I would recommend high def cable and from the looks of this you have only basic cable. I don't mean this in a bad way or anything but you have made the investment in an HDTV so to really enjoy it you need a high def source. Standard definition is not going to look that great on your TV as it was designed to accomodate higher resolution sources. If you went with high def you would also get a cable set top box that you could connect via SPDIF to your RCA system. Have you considered this at all? To answer your question about what SPDIF is.. The simplest answer is that it is a digital data stream versus an analog signal. The red and white connectors you see are stereo and analog. The advantage of the SPDIF is that with the proper signal your receiver can send unique sound to 5 speakers and a subwoofer (with the subwoofer being for bass) and is known as 5.1 digital audio. A simple way of looking at this would be to compare to stereo which I am guessing you understand. With stereo you have 2 speakers, the right and the left, with each speaker having its own unique sound coming from them. Again with 5.1 you have 5 speakers with their own unique sound coming from them. What this is trying to accomplish is to make the sound you hear as close tyo reality as possible. What the SPDIF does is send a digital signal to the receiver and the receiver turns the signal into the unique sound you hear coming from each of the 5 speakers. It looks like your TV is not sending the signal that the RCA needs to do this. Although you might want to make sure you have put the receiver on the correct input selection for the spdif. If you look at the back of the receiver it will tell you what input the SPDIF is -select that one when you are trying to do this. You are going to be somewhat limited in your ability to do this because your receiver only has one digital audio in so unless you use a switch for the SPDIF you will only be able to connect one device in this manner. Otherwise as Jim has suggested you can use the red and white or stereo. This is not going to be true 5.1 but it will be what is called Dolby pro logic which will attempt to convert the stereo signal to surround sound. The only other alternative besides the ones I have listed would be to upgrade to a receiver that will have the correct number of digital inputs and therefore accomodate true 5.1 for the DVD, Cable, etc... |
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Silver Member Username: CclashhPost Number: 233 Registered: Jan-08 | Hey Jim, Know any good places to get an SPDIF switch. I don't know but it would seem that if his TV has a digital coax out that it should work? Maybe its a setting we are missing in the TV's OSD? |
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Silver Member Username: JrbayLivonia Detroit area, Michigan USA Post Number: 182 Registered: Feb-08 | This has all the makings of a new FAQ for my website! Regarding the switch, oh yes there are digital audio switches and they are great but expensive. The ones I see have remote controls, and both RCA and Toslink ins and outs but for nearly $200.00 but why not buy a entry level receiver that would accomplish the same thing and improve the sound to boot? No surprise that there is a lot of conflicting information regarding digital audio out there. What I suspect is a continuation of the (insert famous [large, furry, scary] cable maker here) marketing strategy leading people to believe that if the cable isn't solid gold and cost more than a HTiB then it won't work. So this is my understanding so far (and I rely on the group to correct me if I am wrong) SPDIF is just a protocol or standard that allows two devices to "talk" to each other digitally. There are two types of connectors used for SPDIF that being RCA type and Toslink (mini). Toslink is relatively straight forward in that more expensive than "coax" but I like it because I am absolutely certain that a reasonably well made cable (not the cheapest but pretty darn close)will transfer EXACTLY the same information as the most expensive cable made. There may be issues with how fragile the cable is and how well the connectors fit in the sockets but the signal is passed. "Coax" gets more confusing because anything with an RCA plug on the end it technically "coax". It has a center conductor generally considered to be the positive conductor and a shield generally considered to be the negative conductor. So what is a "digital coax"? What I know is that cheap RCA type cable will work but is likely to cause trouble just like if you use cheap RCA cable to hook up a subwoofer (the one time I tried it the sub would not shut off because of the noise and the wire was replaced!). OK that said, what's the point. Well in this case why wouldn't a composite video switch work? So the bottom line here is: Cheapest way of dealing with this: RED/WHITE audio out from the TV (but Casey says there are no such thing) and the Wii while the DVD can use the digital input. This would work reasonably well. Cheapest way of going digital: Get a cable box and with no guarantee of success try a cheap (returnable) composite video 3 (or 4) in and 1 out switch. Best way: Cable box and a receiver that can switch digital audio. |
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Bronze Member Username: LevelzeroPost Number: 29 Registered: Aug-07 | Casey, What is the model of your television set? I can't imagine a set not having the red/white audio ports these days. |
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Silver Member Username: CclashhPost Number: 234 Registered: Jan-08 | Why does he have spdif and cannot use it. It must be there for some reason. Maybe that has to be enabled? |
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Silver Member Username: JrbayLivonia Detroit area, Michigan USA Post Number: 192 Registered: Feb-08 | I do not think the TV does the Analog to Digital conversion from the RF input at all but if it does then you are right Jeff it would have to be enabled. |
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Gold Member Username: John_sColumbus, Ohio US Post Number: 2255 Registered: Feb-04 | Hi guys. Just to make sure we're on the same page, let me state the obvious: no TV is going to convert analog audio to digital (PCM or Dolby) and pass the signal on its SPDIF output, whether its a signal on its RF in, or any of its analog inputs. It is my understanding that many -- maybe all -- modern TVs pass digital audio only when the signal is received by the ATSC tuner via an ordinary antenna. Apparently cable doesn't count because the TV's QAM tuner is engaged for that. You'd think the TV would pass the digital audio on the digital cable channels (both SD and HD) on its SPDIF output, but that doesn't seem to be the case with most TVs. Since this question comes up all the time here, I've looked up a number of owner's manuals regarding this very question. In no case has the function of the SPDIF out been clearly stated as to what it will or won't do. Who can blame people for being confused? The only thing the 75 page owners manual for one of my TVs says only this: "OPTICAL OUTPUT OF AUDIO RECEIVED WITH HD PROGRAMS "If your sound system has a SPDIF (optical) digital audio input you can connect it to the optical DIGITAL AUDIO OUT at the rear of [this] HDTV. This is active when receiving digital audio with the programs from the DTV/TV CABLE/ANTENNA input." OK, so they saying this applies to HD channels only. But does that mean only over-the-air reception, or does that include any "in the clear" HD channels the QAM tuner picks up on basic cable? I have not tested this TV, because I am not using it with a digital receiver. I am going to run a test next week when I get time. It's going to be a hassle, but inquiring minds need to know.  And yes Jim, this issue would make a very good FAQ on anybody's website. Casey, after you run a cable channel scan on the Philips, do you get any local HD channels? If so, did you not get audio on the TV's coax out on those channels either? |
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Silver Member Username: CclashhPost Number: 235 Registered: Jan-08 | I think we lost Casey  have not seen him since Wed. Thanks John I am really curious as to what purpose the digital out serves on these TV's. I mean it either has a signal or it doesn't. To me if this was only effective for high def stations that would be a serious design flaw simply because of the inconveniences it would cause. I mean you could be watching a high def station and switch to a standard def station and you would have to switch from the receiver back to the TV speakers or switch to another input on the reciver everytime you change a channel -to me that is a really bad idea which leads me to beleive that he must be able to get sound via SPDIF from the TV for any channel? |
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Silver Member Username: JrbayLivonia Detroit area, Michigan USA Post Number: 198 Registered: Feb-08 | You are correct Jeff but at this time next year we will all be lauding this connector as the second best thing since HDMI!!! When everything goes digital I think most of the current issues will be resolved (making room for a whole host of new ones! I trust John, that you will reveal the results of your test, if so I will write a FAQ. We may have lost Casey but being on the same page sure is interesting!  |
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Silver Member Username: MccambleyBREEZY POINT, NY USA Post Number: 489 Registered: Jun-05 | We have seen this question before. The optical out put on a TV is ONLY for the ATSC tuner built into the TV. Hook up a roof antenna to the TV and scan for channels. Once you have found your local stations and display them the sound then will be sent to your receiver from the optical out put. You will not get cable station from this out put or anything else you feed the TV but the antenna feed. |
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Silver Member Username: MccambleyBREEZY POINT, NY USA Post Number: 490 Registered: Jun-05 | My statement about ONLY ATSC tuner is incorrect, it is for both ATSC and the NTSC tuner in your TV. |
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Gold Member Username: John_sColumbus, Ohio US Post Number: 2257 Registered: Feb-04 | Thanks for your input Casey. The question is still what happens with the digital channels a QAM tuner picks up on cable. It seems to me that if the TV sees DD on its RF input -- regardless of whether that source is antenna or cable -- it then should pass this signal on to its digital output intact. |
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Silver Member Username: JrbayLivonia Detroit area, Michigan USA Post Number: 199 Registered: Feb-08 | Do you think there IS any digital information? This is interesting because my understanding was that any true digital cable system needed STB's or cards to work. I have never actually tried plugging in directly I just assumed it wouldn't work. |
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Gold Member Username: John_sColumbus, Ohio US Post Number: 2258 Registered: Feb-04 | "a QAM tuner is a device present in some digital televisions and similar devices which enables direct reception of digital cable channels without the use of a set-top box." http://en.wikipedia.org/wiki/QAM_tuner Casey's Philips TV has NTSC, ATSC, and QAM tuners. |
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New member Username: SoftlyspokenmagicspellsPost Number: 4 Registered: May-08 | Hey guys, sorry I haven't given an update on the situation. Thanks for all of your help and input! The other night, I thought I would give the SPDIF another try. MIRACULOUSLY the thing started working! On my RCA sound system the sound is audible under "DVD/Coax" and "SAT/Coax." I'm pretty darn sure I tried BOTH of those things the other day, so I don't know what changed. Who knows... There's a lot to figure out with these HDTV's. I am just relieved that my TV is not defective. Also, after over-analyzing the situation, I'm not sure HOW it is actually working. Because I don't have a digital tv signal yet, so I'm not sure what sort of sound is coming through the SPDIF. Analog? Oh well. Everything seems to be working now though. Thanks again for all of the advice. |
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Silver Member Username: CclashhPost Number: 236 Registered: Jan-08 | Casey, What are you using to connect the DVD to the TV -HDMI...? Are you getting Dolby Digtial 5.1 when you are playing DVD's? -Just curious... |
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Gold Member Username: John_sColumbus, Ohio US Post Number: 2259 Registered: Feb-04 | OK guys, let me clear up something now. I know Casey you said you only have only one "Digital Audio In", but actually you have two: one coax, and one optical. I assume you have your DVD player hooked up to the optical input, which would yield DD 5.1 in your sound system. You should avoid using the red/white inputs marked "DVD." Also, the reason there's a "Subwoofer Audio Out" jack on your receiver is because I believe RCA sells this receiver with another speaker set that includes a powered subwoofer. This is the connection port for a powered sub. |
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Gold Member Username: John_sColumbus, Ohio US Post Number: 2260 Registered: Feb-04 | For what it's worth, I did run a test on my flat panel's optical output. The TV is a Vizio VX37L, which has NTSC, ATSC, and QAM tuners. This display is a bedroom TV and is normally not used with an external audio system. I connected its optical output to an old 5.1 receiver I no longer use. After running a basic cable channel scan, the TV came up with 88 analog channels and a number of digital channels, including NBC-HD, ABC-HD, CBS-HD, Fox-HD, PBS-HD, and other lesser digital channels. The audio from all the digital channels (including about 35 music channels) came through to the receiver. All the HD channels were DD 5.1. When I tuned in any of the analog channels the TV speakers worked of course, but there was no audio coming out of the optical output into the receiver. I then hooked up a ordinary antenna and ran an antenna channel acan on the TV. As expected, DD 5.1 audio was heard from the (digital) HD channels but not from the analog SD version of those same channels. What I experienced is certainly no guarantee all TVs are going to work the same way. This seems to be the case with Casey's Philips, since he now says he is getting audio from has analog cable channels. I am surprised that any display would digitize ordinary analog audio and feed it from its digital output. |
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Silver Member Username: CclashhPost Number: 237 Registered: Jan-08 | "On my RCA sound system the sound is audible under "DVD/Coax" and "SAT/Coax." The digital inputs on that receiver are assignable so his whole probem could have been that originally he was selecting the optical input for the devices without knowing it. This also explains why the sound is audible on two different inputs coming from one source -the TV because they are both obviously set to Coax. In order for Casey to use the optical input he would need to follow the directions in his manual to assign a second input to optical and use the optical input for another device. For example the TV on SAT/Coax and the DVD on DVD/Optical. |
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