I bought several meters of RCA cable to use as an unbalanced interconnect and am now contemplating matching it with BNC connectors, i.e. from Canare.
Other forum users have praised BNC over Chinch due to the good locking connection and since I am building my stereo by myself, I do not need to use Chinch.
Do you think this is a good idea or should I stick to RCA/Chinch connectors?
If going down the BNC route, which resistance should the BNC connectors have? Canare only has 75 and 50 ohm. Cable specifictions are below.
Conductor resistance: 85 ohm/km
Shielding resistance: 11.30 Ohm/km
Capacitance cond/cond: 70 nF/km
Test voltage: 000 veff (2 minutes)
Link to product
Thank you!!!
Other forum users have praised BNC over Chinch due to the good locking connection and since I am building my stereo by myself, I do not need to use Chinch.
Do you think this is a good idea or should I stick to RCA/Chinch connectors?
If going down the BNC route, which resistance should the BNC connectors have? Canare only has 75 and 50 ohm. Cable specifictions are below.
Conductor resistance: 85 ohm/km
Shielding resistance: 11.30 Ohm/km
Capacitance cond/cond: 70 nF/km
Test voltage: 000 veff (2 minutes)
Link to product
Thank you!!!
85 ohm is the resistance per kilometre length of the cable.
Are you confusing this with the impedance of an interconnect?
Impedance is important for digital interconnects, but for analogue audio, impedance is completely irrelevant until cable lengths get in the many hundreds of metres.
You can use a 75 ohm interconnect for normal audio. Standard phono leads are typically more like 40-50 ohms.
I would say that the cable is suitable for analogue purposes, in conjunction with either 75 or 50 ohm BNC connectors.
Are you confusing this with the impedance of an interconnect?
Impedance is important for digital interconnects, but for analogue audio, impedance is completely irrelevant until cable lengths get in the many hundreds of metres.
You can use a 75 ohm interconnect for normal audio. Standard phono leads are typically more like 40-50 ohms.
I would say that the cable is suitable for analogue purposes, in conjunction with either 75 or 50 ohm BNC connectors.
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They are way better than RCA BUT you will be one of the very few using them for analog L/R signal so interconnecting of friends devices is a no no.
I use 75 Ohm BNC for SPDIF (which uses the 75 Ohm standard) since ages and even though Chinese and Japanese gear makes use of this as well in Europe people are frowning when BNC is used. This while it is technically better. Also the dreaded "resale value" is always present like if we all are building stuff to sell it.
So for SPDIF I would not hesitate to use 75 Ohm cable and BNC connectors (making them non compatible with the analog connectors at the same time which is good) but for analog you will be a lonely audiophile when you fit all your gear with BNC connectors.
I use 75 Ohm BNC for SPDIF (which uses the 75 Ohm standard) since ages and even though Chinese and Japanese gear makes use of this as well in Europe people are frowning when BNC is used. This while it is technically better. Also the dreaded "resale value" is always present like if we all are building stuff to sell it.
So for SPDIF I would not hesitate to use 75 Ohm cable and BNC connectors (making them non compatible with the analog connectors at the same time which is good) but for analog you will be a lonely audiophile when you fit all your gear with BNC connectors.
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You have to arrange cable characteristics impedance and connector impedance only for high-speed (high-frequency) circuits (listen to @Galu). Audio circuits usually don't need that.Do you think this is a good idea or should I stick to RCA/Chinch connectors?
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Since you seem to be willing to go the extra mile for perfection (bnc/rca), have you seen Lemo’s nim/camac?
Very nice stuff, and even more outlandish than bnc 😉
Very nice stuff, and even more outlandish than bnc 😉
Yes, matching is for RF. Youncan get BNC to RCA converters if you want to be compatible.
Impedance of connectors is of no issue in the audio range; think RF frequencies (150kHz & up) for proper application. In AF range any rock solid near zero ohm interconnect will suffice, whatever the lockability, userability, goldmirrorability. Spdif is as stated above, on its own.
Assuming that "cellular PE" means polyethylene foam, 70 pF/m corresponds to a high-frequency characteristic impedance of about 60 ohm. If it is solid polyethylene, the high-frequency characteristic impedance is about 71 ohm. These values apply from a few hundred kilohertz onward.
In either case, it doesn't matter at all for normal analogue audio whether you use 50 ohm or 75 ohm BNC. If you think there is any chance that you will ever use those cables for S/PDIF, then 75 ohm is the logical choice.
In either case, it doesn't matter at all for normal analogue audio whether you use 50 ohm or 75 ohm BNC. If you think there is any chance that you will ever use those cables for S/PDIF, then 75 ohm is the logical choice.
Note to self: never leave a thread unattended and go to sleep 🙂.
I have to work now but will be in touch later on today.
I suspect that you are right and that I might have confused resistance with impedance. Ty! Vovk Z and Galu
I will also respond to the feedback!
I have to work now but will be in touch later on today.
I suspect that you are right and that I might have confused resistance with impedance. Ty! Vovk Z and Galu
I will also respond to the feedback!
I hope it is still polite to respond in a single post to everyone who contributed above.
Galu, yes I am now certain to have confused cable resistance and connector impedance. Thank you for making me aware.
Jean-Paul, yes. I will need to make some special cases for friends that have Chinch on one end. Possible, hypothetical future friends.
For DC current from external power supply to device or wall socket to device?
Vovk Z. This I understand now. Thank you. I read an interesting blog post on this topic here today.
myleftear I have seen Lemo’s nim / camac, although I did not go so far as to select a concrete model. I like that they are outlandish. They appear to cost quite a bit more than bnc connectors.
cbdb Yes, thank you. I have spotted the converters now 🙂
MarsBravo Yes, I understand now. Thank you. I mean, I understand that it is so, although I need to still understand the physics behind it. I will follow up on this later.
However, this brings the question, how do people choose alternatives to RCA connectors at all? Will actually any mechanically suitable 2 pole connector near zero ohm (do you mean now resistance or impedance?) suffice?
MarcelvdG, thank you. I will go for 75 ohm to keep my options open for the future. Now I just need to find a good connector. Canare seems to be rare in Germany.
I did not know that the isolation could affect the capacitance in such a way.
Galu, yes I am now certain to have confused cable resistance and connector impedance. Thank you for making me aware.
Jean-Paul, yes. I will need to make some special cases for friends that have Chinch on one end. Possible, hypothetical future friends.
For DC current from external power supply to device or wall socket to device?
Vovk Z. This I understand now. Thank you. I read an interesting blog post on this topic here today.
myleftear I have seen Lemo’s nim / camac, although I did not go so far as to select a concrete model. I like that they are outlandish. They appear to cost quite a bit more than bnc connectors.
cbdb Yes, thank you. I have spotted the converters now 🙂
MarsBravo Yes, I understand now. Thank you. I mean, I understand that it is so, although I need to still understand the physics behind it. I will follow up on this later.
However, this brings the question, how do people choose alternatives to RCA connectors at all? Will actually any mechanically suitable 2 pole connector near zero ohm (do you mean now resistance or impedance?) suffice?
MarcelvdG, thank you. I will go for 75 ohm to keep my options open for the future. Now I just need to find a good connector. Canare seems to be rare in Germany.
I did not know that the isolation could affect the capacitance in such a way.
Locking? Is your cat pulling cables out? (OK, I had classroom record players where wires got disconnected, nobody knew how it happened.... 😕 )
I've had BNC network connectors (yes, I am not as young as I look) come loose, again "for no reason".
I hate cinch/RCA too but it may be the best of our affordable choices. (And no bag of odd adapters to use with "other" gear.)
The "85" ohms (really 96 ohms) is a series loss for exactly one kilometer. They won't even sell you a whole km, and I think you don't have the 100m reel? And 100 meters of even the best unbalanced cable is begging for radio and fluorescent interference, we normally work audio coax at 1 to 10 meter lengths.
The 50 or 75 ohms is a shunt impedance at infinite length or frequency. It does not matter at audio.
Curious, I ran a 10-lump approximation for a 10 meter cable. Inside the audio band it is always >10,000 Ohms. Out at 3MHz it approaches 100 Ohms, and the asymptotic Z is surely 50 to 200 Ohms, but deeply swamped by the relatively huge 96r/km copper loss (which of course is insignificant against the 10k audio impedance).
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BNC vs RCA
The big advantage of BNC over RCA is that BNC has a controlled pin depth for it's center connector. This is of importance at RF frequencies, but does not matter at audio frequencies, which is why the BNC is considered superior to RCA for SPDIF.
The difference between 50ohm and 75ohm also applies to RF frequencies, and refers to the caracteristic impedance of the cable. The impedance of the cable, connector, and the equipment being hooked up all have to match. SPDIF and analog video use 75ohm, while most of the RF world uses 50ohm.
For audio, the only advantage to BNC would be the locking connectors keep the cables from coming unplugged.
The big advantage of BNC over RCA is that BNC has a controlled pin depth for it's center connector. This is of importance at RF frequencies, but does not matter at audio frequencies, which is why the BNC is considered superior to RCA for SPDIF.
The difference between 50ohm and 75ohm also applies to RF frequencies, and refers to the caracteristic impedance of the cable. The impedance of the cable, connector, and the equipment being hooked up all have to match. SPDIF and analog video use 75ohm, while most of the RF world uses 50ohm.
For audio, the only advantage to BNC would be the locking connectors keep the cables from coming unplugged.
I know of the drawbacks of being an alien just by having other plugs. Just like naim still sticks to their DIN (?) plugs, and Conrad being sort of forced to convert back from the nim-camacs...
OTOH, I always have to smile/grin when I see those ahem-highend RCA-connector which come with a locking-method of sorts...
To me, the main disadvantage of cinch connectors is their unreliability. In the good old days when the local radio station here still had mainly analogue equipment, we sometimes had problems related to cinch connector grounds that got disconnected. We never had problems with XLR connectors, even though there were far more XLR than cinch connectors in use. I can't comment on BNC reliability as we used only a few of those.
Thank you everyone for sharing. I synthesize:
For unbalanced audio BNC has the following advantages over RCA: locking, higher reliability
For unbalanced audio connector impedance does not need to match cable impedance. This only matters for higher frequency signals.
The disadvantage of using BNC instead of RCA is a lack of compatibility.
Thank you!
@PRR
For unbalanced audio BNC has the following advantages over RCA: locking, higher reliability
For unbalanced audio connector impedance does not need to match cable impedance. This only matters for higher frequency signals.
The disadvantage of using BNC instead of RCA is a lack of compatibility.
Thank you!
@PRR
As a non-engineer, I cannot follow. However, it looks like a cool simulation.
I have no intention of simulating anything, but the inductance can easily be calculated from the type of dielectric and the capacitance:
v = 1/sqrt(L C) where v is the speed of propagation and L and C are the inductance and capacitance per unit length
Hence, L = 1/(v^2 C)
C is specified as max. 70 pF/m. The dielectric is described as cellular PE. If that means polyethylene foam, then v is about 80 % of the speed of light in vacuum, if it is solid polyethylene, v is about two thirds of the speed of light in vacuum.
Hence, with 70 pF/m, L is about 248 nH/m for foam and about 358 nH/m for solid PE. The high-frequency asymptote of the characteristic impedance is sqrt(L/C).
v = 1/sqrt(L C) where v is the speed of propagation and L and C are the inductance and capacitance per unit length
Hence, L = 1/(v^2 C)
C is specified as max. 70 pF/m. The dielectric is described as cellular PE. If that means polyethylene foam, then v is about 80 % of the speed of light in vacuum, if it is solid polyethylene, v is about two thirds of the speed of light in vacuum.
Hence, with 70 pF/m, L is about 248 nH/m for foam and about 358 nH/m for solid PE. The high-frequency asymptote of the characteristic impedance is sqrt(L/C).
The big advantage of BNC and nearly every other connector out there over RCA is that the shield mates first. Most audio equipment is not earthed, so it sits at half mains at a high impedance until plugged in. Plugging in a RCA powered up all too often blows ICs