Hi everyone,
I'm a bit new to the forums so nice to meet all of you.
I want to run digital audio from my PC to home stereo. I've just upgraded to an SBLive! soundcard with digital out. Previously I'd been using the analog front and left, routed through a thin telephone-like three conductor wire to my stereo, about 50ft away from the PC. It worked fine.
When I put in the SB card the analog worked fine there as well. So I cut off the phono plugs and put RCA's on this same cable and ran it from the SPDIF out on my Sound Blaster to the digital in of my receiver: Nothing.
I checked the cable, and there's no short or any such. Thinking the digital signal may be too weak to travel that distance on such a small wire, I ran a 16 gauge speaker wire the entire distance, and still, not a peep from the receiver.
Finally, I lugged my entire PC into the living room, and hooked them together with a two foot RCA cable. It worked and sounded perfect, so I know there's not a problem with my soundcard or receiver.
Unless someone else has any theories, my guess is that the power output on the SB card's digital out is rather low. If that's so, I guess I need to wire up a signal amplifier.
On the suggestion of another I tried one of those 3-volt Radio Shack headphone amps. Still didn't work, I'm thinking the amplifying transistors in the circuitry aren't made to switch at the high speeds needed for a digital signal.
What do you all think?
Does anyone have experience with this? Surely others want to hear digital music in a different room.
Well, thanks in advance for any help!
I'm a bit new to the forums so nice to meet all of you.
I want to run digital audio from my PC to home stereo. I've just upgraded to an SBLive! soundcard with digital out. Previously I'd been using the analog front and left, routed through a thin telephone-like three conductor wire to my stereo, about 50ft away from the PC. It worked fine.
When I put in the SB card the analog worked fine there as well. So I cut off the phono plugs and put RCA's on this same cable and ran it from the SPDIF out on my Sound Blaster to the digital in of my receiver: Nothing.
I checked the cable, and there's no short or any such. Thinking the digital signal may be too weak to travel that distance on such a small wire, I ran a 16 gauge speaker wire the entire distance, and still, not a peep from the receiver.
Finally, I lugged my entire PC into the living room, and hooked them together with a two foot RCA cable. It worked and sounded perfect, so I know there's not a problem with my soundcard or receiver.
Unless someone else has any theories, my guess is that the power output on the SB card's digital out is rather low. If that's so, I guess I need to wire up a signal amplifier.
On the suggestion of another I tried one of those 3-volt Radio Shack headphone amps. Still didn't work, I'm thinking the amplifying transistors in the circuitry aren't made to switch at the high speeds needed for a digital signal.
What do you all think?
Does anyone have experience with this? Surely others want to hear digital music in a different room.
Well, thanks in advance for any help!
A perfect solution to your problem might be a "customized" link similar to the one Elso Kwak suggested in the "digital transformer" thread some time ago.
You would pick up the S/PDIF signal at TTL level somewhere inside your soundcard, "boost" it with 74xx logic and drive a twisted pair cable balanced. At the receiving end, a proper line termination followed by a fast comparator can convert the signal back to TTL level.
You would pick up the S/PDIF signal at TTL level somewhere inside your soundcard, "boost" it with 74xx logic and drive a twisted pair cable balanced. At the receiving end, a proper line termination followed by a fast comparator can convert the signal back to TTL level.
After re-reading your post, one more hint: Your entire connection should be a 75 Ohm coaxial connection. Speaker cable or telephone wire will NOT work with a standard S/PDIF interface. Impedance matching matters more the longer the cable is. A standard S/PDIF connection was not designed for 50 ft cable length AFAIK, but it might work anyway. If you don't get it to work, a customized interface (as mentioned above) is the way to go.
Long Distance SPDIF
Hi Luke,
I tested my interface in the digital transformer thread with 13m (that is about 42 feet) common 75 Ohm coax. I did not hear any quality loss.
http://www.diyaudio.com/forums/showthread.php?postid=44053#post44053
For best results use double shielded coax and 75 Ohm BNC connector system.
Hi Luke,
I tested my interface in the digital transformer thread with 13m (that is about 42 feet) common 75 Ohm coax. I did not hear any quality loss.
http://www.diyaudio.com/forums/showthread.php?postid=44053#post44053
For best results use double shielded coax and 75 Ohm BNC connector system.
SPDIF in the long run.....
Actualy is the oposite see the caracteristics of the standard IEC958 Digital Audio Interface.
-Cable: 75ohm +/-5% (l<10m) or 75ohm +/-35% (l>10m)
As stated with more than 10 meters runs the inpedance of the cable can have a tolerance of 35%.
For more information(for the fews that do the home work)see:
http://www.epanorama.net/documents/audio/spdif.html
Regards
Jorge
Actualy is the oposite see the caracteristics of the standard IEC958 Digital Audio Interface.
-Cable: 75ohm +/-5% (l<10m) or 75ohm +/-35% (l>10m)
As stated with more than 10 meters runs the inpedance of the cable can have a tolerance of 35%.
For more information(for the fews that do the home work)see:
http://www.epanorama.net/documents/audio/spdif.html
Regards
Jorge
When dealing with digital audio and all flavors of video: Match your impedences. All along the path.
For S/PDIF: Use a 75 coax ohm cable. Belden cable model 1694 is excellent, but just about any 75 ohm cable should work.
If the connectors are BNC type, make sure you are using 75 ohm BNC connectors.
If the connections are RCA/Phone types, use a good quality connector. I do not know of any RCA/Phono connectors rated at 75 ohm.
If you have some restrictions that you are forced to use existing twisted pair cabling, you can use 75 ohm to 110 ohm transformers on the output, go through the twisted pair, then go 110 ohm to 75 ohm at your destination.
The transformers will cost more than 50 ft of 75 ohm coax plus connectors, so if you can re-run your cable, that is the way to go.
Aud_Mot
For S/PDIF: Use a 75 coax ohm cable. Belden cable model 1694 is excellent, but just about any 75 ohm cable should work.
If the connectors are BNC type, make sure you are using 75 ohm BNC connectors.
If the connections are RCA/Phone types, use a good quality connector. I do not know of any RCA/Phono connectors rated at 75 ohm.
If you have some restrictions that you are forced to use existing twisted pair cabling, you can use 75 ohm to 110 ohm transformers on the output, go through the twisted pair, then go 110 ohm to 75 ohm at your destination.
The transformers will cost more than 50 ft of 75 ohm coax plus connectors, so if you can re-run your cable, that is the way to go.
Aud_Mot
It works!
Ok,
I tried the coax and voila! Though the cable is connecting to RCA's on both ends, Radio Snack has nice screw-on adaptors from BNC to RCA. Turns out, the best solution was also the easiest one. I was even able to get white coax, you can't hardly see it along the wall.
Thanks everyone for the advice, these forums are great!
Ok,
I tried the coax and voila! Though the cable is connecting to RCA's on both ends, Radio Snack has nice screw-on adaptors from BNC to RCA. Turns out, the best solution was also the easiest one. I was even able to get white coax, you can't hardly see it along the wall.
Thanks everyone for the advice, these forums are great!
Transformer
Sorry,
I first discovered this thread after starting anew one. Look what I did....
http://www.diyaudio.com/forums/showthread.php?s=&threadid=54683
Sorry,
I first discovered this thread after starting anew one. Look what I did....
http://www.diyaudio.com/forums/showthread.php?s=&threadid=54683
Re: It works!
ditch the adapters, get BNC into the components and you'll be even happier. Especially at the receiver side, you want 75 ohm hardware all the way through, although with the long cable you have you probably won't see a siginificant improvement. It actually helps you by attenuating the reflected signal.
Peter
Luke M. said:
ditch the adapters, get BNC into the components and you'll be even happier. Especially at the receiver side, you want 75 ohm hardware all the way through, although with the long cable you have you probably won't see a siginificant improvement. It actually helps you by attenuating the reflected signal.
Peter
Hi everybody.
My setup is very similar to Luke's, as is my problem (although he seems to have solved his already).
Today I went out and bought 20m (60ft) of Tasker RGB75 coaxial cable and took care to connect good quality connectors on both ends. One being a mono 3.5mm jack plug (for the sound card digital out) and the other, an rca connector.
Hooked everything up and....nothing. By chance I discovered that if I only connect the signal pin of the RCA plug to the RCA digital input on my DAC, then it works fine.
Hooked up as a mono analog interconnect, the cable works fine, so it's wired correctly.
How is this possible?
My setup is very similar to Luke's, as is my problem (although he seems to have solved his already).
Today I went out and bought 20m (60ft) of Tasker RGB75 coaxial cable and took care to connect good quality connectors on both ends. One being a mono 3.5mm jack plug (for the sound card digital out) and the other, an rca connector.
Hooked everything up and....nothing. By chance I discovered that if I only connect the signal pin of the RCA plug to the RCA digital input on my DAC, then it works fine.
Hooked up as a mono analog interconnect, the cable works fine, so it's wired correctly.
How is this possible?
Breaker said:Hi everybody.
My setup is very similar to Luke's, as is my problem (although he seems to have solved his already).
Today I went out and bought 20m (60ft) of Tasker RGB75 coaxial cable and took care to connect good quality connectors on both ends. One being a mono 3.5mm jack plug (for the sound card digital out) and the other, an rca connector.
Hooked everything up and....nothing. By chance I discovered that if I only connect the signal pin of the RCA plug to the RCA digital input on my DAC, then it works fine.
Hooked up as a mono analog interconnect, the cable works fine, so it's wired correctly.
How is this possible?
Groundloop?
Thanks for the reply Elso
I did the following:
I have a ground loop isolator for (analog) audio use, so I put that in the signal path. Now I get no usable signal at all to my DAC.
I'm still unclear as to why the cable is not functioning as it should.
Let's assume the cable is wired correctly, as I'm sure it is. What would be my next step.
The cable is 75 Ohm and I managed to find that it has a resistance of 210 Ohms per km, that means this cable would have a 0,4 Ohm DC resistance. Is it just too long, surely not?
I'm reading about 0,1 V AC and 1,2 V DC at the RCA end.
Any suggestions are welcome.
I did the following:
I have a ground loop isolator for (analog) audio use, so I put that in the signal path. Now I get no usable signal at all to my DAC.
I'm still unclear as to why the cable is not functioning as it should.
Let's assume the cable is wired correctly, as I'm sure it is. What would be my next step.
The cable is 75 Ohm and I managed to find that it has a resistance of 210 Ohms per km, that means this cable would have a 0,4 Ohm DC resistance. Is it just too long, surely not?
I'm reading about 0,1 V AC and 1,2 V DC at the RCA end.
Any suggestions are welcome.
An audio ground isolator (breaker) is probably designed for audio frequency (44.1KHz). Digital spdif means megahertz (bitrate for stereo signal is aroung 1mbit).
You can either try with a ground breaker designed for cable (hundreds of megahertz there) or build one. Simplest one may be a 1:1 transformator build on a ferrite ring (from a dead pb mb) having 15 turns of wire recovered from a network cable (I think it's 0.4mm copper) on each winding and a 100nF capacitor in series with the input.
You can either try with a ground breaker designed for cable (hundreds of megahertz there) or build one. Simplest one may be a 1:1 transformator build on a ferrite ring (from a dead pb mb) having 15 turns of wire recovered from a network cable (I think it's 0.4mm copper) on each winding and a 100nF capacitor in series with the input.
First off..........
DC resistance and characteristic impedance are 2 very different things. One you read with an ohmmeter, the other needs a network analyser or TDR to measure. Since I know that you have neither of the last 2...........forget what the DCR is.
And just how are you measuring this signal?? I hope not with a DMM. Don't laugh.........I know guys who do.
Anyway............hook it up to your 'scope. Measure it with a 75R termination, and tell us what you get. Both level and any DC offset. (Should not be any of the latter.)
Jocko
DC resistance and characteristic impedance are 2 very different things. One you read with an ohmmeter, the other needs a network analyser or TDR to measure. Since I know that you have neither of the last 2...........forget what the DCR is.
And just how are you measuring this signal?? I hope not with a DMM. Don't laugh.........I know guys who do.
Anyway............hook it up to your 'scope. Measure it with a 75R termination, and tell us what you get. Both level and any DC offset. (Should not be any of the latter.)
Jocko
Thanks guys,
I must disappoint and admit to using a DMM to get the readings I mentioned. I know that resistance and impedance are different, and I mentioned the measurements as a kind of afterthought (I whipped out the DMM while typing the post), hoping that they might just means something to somebody, but as Jocko politely implies, they probably aren't worth much. Unfortunately I don't have a scope, so the DMM is as good as it gets. 
I'll try and scavenge the parts for the RF ground breaker danb1974 described. Hopefully that will improve things.
I know that there are pretty large differences between the 'grounds' of may various hifi components and my PC...I can literally feel the buzz! Unfortunately my kitchen is the only room in my appartment with earthing in the wiring, so creating a common earth/ground for my equipment is a challenge. I might give it a go though.
I must disappoint and admit to using a DMM to get the readings I mentioned. I know that resistance and impedance are different, and I mentioned the measurements as a kind of afterthought (I whipped out the DMM while typing the post
), hoping that they might just means something to somebody, but as Jocko politely implies, they probably aren't worth much. Unfortunately I don't have a scope, so the DMM is as good as it gets. I'll try and scavenge the parts for the RF ground breaker danb1974 described. Hopefully that will improve things.
I know that there are pretty large differences between the 'grounds' of may various hifi components and my PC...I can literally feel the buzz! Unfortunately my kitchen is the only room in my appartment with earthing in the wiring, so creating a common earth/ground for my equipment is a challenge. I might give it a go though.
Ok.......so you need a pulse transformer to break up the ground loop.
If you put it on on the RX side, you can use it come up with a differential output to the RX chip.
Newava makes a good one. Pulse Engineering is ok. I do not like the Scientific Conversions models, despite all their hype. Whatever you do, make sure that it is a 1:1 model.
Jocko
If you put it on on the RX side, you can use it come up with a differential output to the RX chip.
Newava makes a good one. Pulse Engineering is ok. I do not like the Scientific Conversions models, despite all their hype. Whatever you do, make sure that it is a 1:1 model.
Jocko
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.